Simulations Of Dynamical Evolution Research Articles

Simulation of Dynamic Evolution of Ring Current Ion Flux by a Lunar Base Energetic Neutral Atom (ENA) Imaging

The distribution of energetic ion flux in the ring current region, such as a meteorological cumulonimbus cloud, stores up the particle energy for a geomagnetic substorm. It is helpful to study the geomagnetic substorm mechanism by using a lunar base ENA imaging simulation of the dynamic evolution of the ring current, and establishing the corresponding relationship between key node events of the substorm. Based on the previous observation experience and our simulation results of the dynamic evolution of the ring current, we propose a macroscopic model of substorms related to the dynamic evolution of ring currents and present the possibility of confirming the causal sequence of some of those critical node events of substorms with the lunar base ENA imaging measurement. IBEX, operating in the ecliptic plane, may even give examples of the telemetry of ring current ion fluxes through ENA measurements during substorms/quiets.

Personal sustained cooperation based on networked evolutionary game theory

Evolutionary game theory on complex networks provides an effective theoretical tool to explain the emergence of sustained cooperative behavior. Human society has formed various organizational networks. The network structure and individual behavior take on a variety of forms. This diversity provides the basis for choice, so it is crucial for the emergence of cooperation. This article provides a dynamic algorithm for individual network evolution, and calculates the importance of different nodes in the network evolution process. In the dynamic evolution simulation, the probability of the cooperation strategy and betrayal strategy is described. In the individual interaction network, cooperative behavior will promote the continuous evolution of individual relationships and form a better aggregative interpersonal network. The interpersonal network of betrayal has been in a relatively loose state, and its continuity must rely on the participation of new nodes, but there will be certain "weak links" in the existing nodes of the network.

Dynamic Evolution Simulation of Bus Bunching Affected by Traffic Operation State

Dynamic Evolution Simulation of Bus Bunching Affected by Traffic Operation State

Modelling self-interacting dark matter substructures – I. Calibration with N-body simulations of a Milky-Way-sized halo and its satellite

ABSTRACT We study evolution of single subhaloes with their masses of ∼109 M⊙ in a Milky Way-sized host halo for self-interacting dark matter (SIDM) models. We perform dark-matter-only N-body simulations of dynamical evolution of individual subhaloes orbiting its host by varying self-scattering cross-sections (including a velocity-dependent scenario), subhalo orbits, and internal properties of the subhalo. We calibrate a gravothermal fluid model to predict time evolution in spherical mass density profiles of isolated SIDM haloes with the simulations. We find that tidal effects of SIDM subhaloes can be described with a framework developed for the case of collision-less cold dark matter (CDM), but a shorter typical time-scale for the mass loss due to tidal stripping is required to explain our SIDM simulation results. As long as the cross-section is less than $\sim \! 10\, \mathrm{cm}^2\,\mathrm{g}^{ -1}$ and initial states of subhaloes are set within a 2σ-level scatter at redshifts of ∼2 predicted by the standard ΛCDM cosmology, our simulations do not exhibit a prominent feature of gravothermal collapse in the subhalo central density for 10 Gyr. We develop a semi-analytic model of SIDM subhaloes in a time-evolving density core of the host with tidal stripping and self-scattering ram pressure effects. Our semi-analytic approach provides a simple, efficient, and physically intuitive prediction of SIDM subhaloes, but further improvements are needed to account for baryonic effects in the host and the gravothermal instability accelerated by tidal stripping effects.

Urban food-energy-water nexus: a case study in Beijing

Food, energy and water (FEW) are indispensable, irreplaceable and safeguarding resources with tangled interlinkages among each other, often framed in terms of ‘nexus’. Cities have become the bustling hubs of resource consumption and production, facing the most intense stress. Globally, food security, fresh water shortage and fossil energy exhaustion have become the greatest challenge for the sustainable development of cities in the future. Systematic analysis and simulation of dynamic evolution of urban FEW demand and supply and its nexus would add significant and practical value for macro-management such as ensuring the security of urban resource. Taking Beijing as the case study, we established a dynamic model for the FEW demand and supply from the perspective of cross-ectoral and cross-regional nexus with the Stella modelling platform, then it was run for simulating the dynamic changes and nexus characteristics of FEW during the interval between 2016 and 2035.The results showed that:①The gap between local production and demand of these three resources in Beijing will continue to increase. In 2035, Beijing will need 2.16 million tons of grain, 0.83 million tons of meat, 4.6 billion m3 of water and 91.65 million tons of standard coal of energy while the resources produced and supplied by locality independently will be 0.21 million tons, 0.23 million tons, 3.3 billion cubic meters and 16.5 million tons of standard coal respectively. Beijing has to draw on cross-boundary production to meet FEW-use with the increasing gap between local supply and demand. ②There is a developing trend of the absolute quantity of interaction among FEW. Structurally, the ‘outsourcing’ feature is obvious and the indigenous nexus links of three resources are shifting to back-end supply chain such as transportation and treatment. ③The change of nexus indexes are mainly affected by the mutual and strong dependence between food and water. Food and energy depend more and more on each other; in contrast, the inter-relationship between water and energy is more stable. In addition, inter-regional FEW nexus is strengthened. ④To improve systematic management of urban resources, we need to capture multi-tradeoffs of the FEW system comprehensively and establish a multi-regional and multi-factor integrated and collaborative resource management mechanism.

Dynamic evolution simulation of sintering pool in selective laser sintering walnut shell/Co-PES composite

In view of the difficulties in the observation of sintering pool and too many factors influencing the dynamic evolution process of sintering pool during the selective laser sintering (SLS) process of biomass composite materials, the structural morphology of sintering pool during the SLS process of walnut shell/Co-PES (WSPC) powder and its dynamic evolution process were studied. Based on the DFLUX subprogram, a moving double ellipsoid heat source model was established. Considering heat conduction, heat radiation, heat convection and thermophysical parameters changing with temperature, the three-dimensional finite element model of WSPC powder was numerically simulated in the process of SLS. Through numerical simulation analysis, the surface shape of sintering pool is circularand the cross section one is deep bowl, and the sintering forming process is a process in which the sintering pool is continuously superposed along the sintering direction. By comparing the experimental results with the numerical simulated results, the experimental results are in good agreement with the simulated results. The dynamic evolution law of sintering pool during SLS process of WSPC powder and the change law that sintering pool size increases with the increase of preheating temperature and laser power and the decrease of scanning speed were obtained.

Water transport throughout the TRAPPIST-1 system: the role of planetesimals

ABSTRACT Observational data suggest that a belt of planetesimals is expected close to the snow line in protoplanetary discs. Assuming there is such a belt in the TRAPPIST-1 system, we examine possibilities of water delivery to the planets via planetesimals from the belt. The study is accomplished by numerical simulations of dynamical evolution of a hypothetical planetesimal belt. Our results show that the inner part of the belt is dynamically unstable and planetesimals located in this region are quickly scattered away, with many of them entering the region around the planets. The main dynamical mechanism responsible for the instability are close encounters with the outermost planet Trappist-1h. A low-order mean-motion resonance 2:3 with Trappist-1h, located in the same region, also contributes to the objects transport. In our nominal model, the planets have received a non-negligible amount of water, with the smallest amount of 15 per cent of the current Earth’s water amount (EWA) being delivered to the planet 1b, while the planets Trappist-1e and Trappist-1g have received more than 60 per cent of the EWA. We have found that while the estimated efficiency of water transport to the planets is robust, the amount of water delivered to each planet may vary significantly, depending on the initial masses and orbits of the planets. The estimated dynamical ‘half-lives’ have shown that the impactors’ source region should be emptied in less then 1 Myr. Therefore, the obtained results suggest that the transport of planetesimals through the system preferably occurs during an early phase of the planetary system evolution.

Research on the Construction of Early Warning Index System of Network Public Opinion Emergency Based on Computer Simulation

Under the current social background of our country, the dissemination environment, dissemination background, audience characteristics, media environment and event types of network public opinion are constantly developing and changing, and the influencing factors will also have new changes. The early warning index system of network public opinion emergencies is an important part of the crisis management of network public opinion. The analysis of network public opinion is based on the complete and accurate grasp of network public opinion. The early warning of network public opinion emergencies is based on the full exploitation and utilization of network public opinion data. Through the analysis and judgment of public opinion, the early warning mechanism of network public opinion emergencies can be improved. Computer simulation is a fast and economical important research tool, and the effectiveness and accuracy of computer simulation depends on the performance of computer simulation software tools. Using computer simulation and simulation of the process of user concept in event propagation, dynamic evolution simulation of events is analyzed according to the results of user concept, and hot events are identified.

Research on the Construction of Early Warning Index System of Network Public Opinion Emergency Based on Computer Simulation

Under the current social background of our country, the dissemination environment, dissemination background, audience characteristics, media environment and event types of network public opinion are constantly developing and changing, and the influencing factors will also have new changes. The early warning index system of network public opinion emergencies is an important part of the crisis management of network public opinion. The analysis of network public opinion is based on the complete and accurate grasp of network public opinion. The early warning of network public opinion emergencies is based on the full exploitation and utilization of network public opinion data. Through the analysis and judgment of public opinion, the early warning mechanism of network public opinion emergencies can be improved. Computer simulation is a fast and economical important research tool, and the effectiveness and accuracy of computer simulation depends on the performance of computer simulation software tools. Using computer simulation and simulation of the process of user concept in event propagation, dynamic evolution simulation of events is analyzed according to the results of user concept, and hot events are identified.

Research on Dynamic Evolution Simulation and Sustainability Evaluation Model of China’s Power Supply and Demand System

Power supply and demand systems are important support systems for industrial production and residents’ lives. They have multiple influencing factors, and complex mechanisms of interaction exist among these factors. In view of the present sustainability problems faced by China’s power supply and demand system, this research adopts a system dynamics (SD) model to simulate the evolution of China’s power supply and demand system, and analyzes the interaction mechanism of various elements of the system. Based on this, an innovative index system for the evaluation of the sustainability of power supply and demand systems is proposed based on the four elements of total amount, structure, technology and environment. Furthermore, by integrating Principal Component Analysis (PCA) and State Space (SS) method, a PCA-SS evaluation model is constructed to explore the development bottleneck of China’s power supply and demand system. The results show that there is still a large gap between the actual sustainability and the ideal range, and that the sustainability of structural and environmental layers needs further improvement. This research expands the knowledge system regarding the evaluation of the sustainability of power supply and demand systems and provides a theoretical reference for the optimization of China’s power supply and demand system.

Hyperdynamics made simple: Accelerated molecular dynamics with the Bond-Boost method

Hyperdynamics methods have significant potential for accelerating simulations of dynamical evolution in solids and solid-like materials, which is mediated by rare events. In this paper, we illustrate the main concepts associated with understanding hyperdynamics through a series of one-dimensional examples. These examples, which are mostly based on the Bond-Boost method, indicate the rigor of hyperdyamics methods and their potential to resolve key bottle-necks in simulating long-time evolution of materials. A significant advantage of hyperdynamics methods is their capability to resolve the small-barrier problem, which is ubiquitous in materials simulation. We present a simple boost potential with benefits for solving the small-barrier problem and discuss future challenges in hyperdynamics simulations.

Research on Comparison and Evolution Mobile Customers Participate Type in Open Innovation

Mobile Customer participation type in open innovation, enterprise innovation development path, needs to address important issues. This paper proposed mobile customer sto participate typology based on three dimensions, which are the customers’ autonomy in the process, the nature of the firm‐customer collaboration, and the stage of the innovation process. Then proposed mobile customers to participate in the type of open innovation framework. Through the static comparative and dynamic evolution simulation found: mobile customers tend to be open to participate in the development of new products pre innovation, the tendency to begin to choose the low participation of degrees of freedom, and ultimately tend to opt for a high degree of freedom to participate.

Research on Simulation Customers Participate Type in Open Innovation

This paper proposed customers to participate typology based on three dimensions, which are the customers’ autonomy in the process, the nature of the firm‐customer collaboration, and the stage of the innovation process. Then proposed customers to participate in the type of open innovation framework. Through the static comparative and dynamic evolution simulation found: customers tend to be open to participate in the development of new products pre innovation, the tendency to begin to choose the low participation of degrees of freedom, and ultimately tend to opt for a high degree of freedom to participate.

Corrigendum to “Medical image analysis methods in MR/CT-imaged acute–subacute ischemic stroke lesion: Segmentation, prediction and insights into dynamic evolution simulation models. A critical appraisal” [NeuroImage: Clinical 1 (2012) 164–178

[This corrects the article DOI: 10.1016/j.nicl.2012.10.003.].

Medical image analysis methods in MR/CT-imaged acute-subacute ischemic stroke lesion: Segmentation, prediction and insights into dynamic evolution simulation models. A critical appraisal.

Over the last 15 years, basic thresholding techniques in combination with standard statistical correlation-based data analysis tools have been widely used to investigate different aspects of evolution of acute or subacute to late stage ischemic stroke in both human and animal data. Yet, a wave of biology-dependent and imaging-dependent issues is still untackled pointing towards the key question: “how does an ischemic stroke evolve?” Paving the way for potential answers to this question, both magnetic resonance (MRI) and CT (computed tomography) images have been used to visualize the lesion extent, either with or without spatial distinction between dead and salvageable tissue. Combining diffusion and perfusion imaging modalities may provide the possibility of predicting further tissue recovery or eventual necrosis. Going beyond these basic thresholding techniques, in this critical appraisal, we explore different semi-automatic or fully automatic 2D/3D medical image analysis methods and mathematical models applied to human, animal (rats/rodents) and/or synthetic ischemic stroke to tackle one of the following three problems: (1) segmentation of infarcted and/or salvageable (also called penumbral) tissue, (2) prediction of final ischemic tissue fate (death or recovery) and (3) dynamic simulation of the lesion core and/or penumbra evolution. To highlight the key features in the reviewed segmentation and prediction methods, we propose a common categorization pattern. We also emphasize some key aspects of the methods such as the imaging modalities required to build and test the presented approach, the number of patients/animals or synthetic samples, the use of external user interaction and the methods of assessment (clinical or imaging-based). Furthermore, we investigate how any key difficulties, posed by the evolution of stroke such as swelling or reperfusion, were detected (or not) by each method. In the absence of any imaging-based macroscopic dynamic model applied to ischemic stroke, we have insights into relevant microscopic dynamic models simulating the evolution of brain ischemia in the hope to further promising and challenging 4D imaging-based dynamic models. By depicting the major pitfalls and the advanced aspects of the different reviewed methods, we present an overall critique of their performances and concluded our discussion by suggesting some recommendations for future research work focusing on one or more of the three addressed problems.

Evolution of Massive Black Hole Triples. I. Equal‐Mass Binary‐Single Systems

We present the results of N-body simulations of dynamical evolution of triple massive black hole (BH) systems in galactic nuclei. We found that in most cases two of the three BHs merge through gravitational wave (GW) radiation in a timescale much shorter than the Hubble time before ejecting one BH through a slingshot. In order for a binary BH to merge before ejecting the third one, it has to become highly eccentric, since the GW timescale would be much longer than the Hubble time unless the eccentricity is very high. We found that two mechanisms drive the increase of the eccentricity of the binary. One is the strong binary-single BH interaction, which results in the thermalization of the eccentricity. The second is the Kozai mechanism, which drives the cyclic change of the inclination and eccentricity of the inner binary of a stable hierarchical triple system. Our result implies that many supermassive BHs are binaries.

Simulation of Dynamic Failure Evolution in Brittle Solids without Using Nonlocal Terms in the Strain-Stress Space

Simulation of Dynamic Failure Evolution in Brittle Solids without Using Nonlocal Terms in the Strain-Stress Space

Solitary waves in asymmetric coupled waveguides with quadratic nonlinearity

By means of direct numerical methods, we study spatial solitons and their stability in a pair of asymmetric linearly coupled waveguides with intrinsic quadratic nonlinearity. Two cases are considered in detail, viz., when the coupling constants at the fundamental and second harmonics are equal, and when the coupling at the second harmonic is absent. These cases correspond to the physical situations in which the coupled waveguides are, respectively, closely or widely separated. Two different kinds of the asymmetry between the waveguides are considered. The first corresponds to a difference in the phase mismatch between the fundamental and second harmonics in the two cores. Unfoldings of the previously known bifurcation diagrams for the symmetric coupler are studied in detail, and the stability of different branches of the solutions are tested. Simulations of dynamical evolution of unstable solitons demonstrate a trend of their rearrangement into stable solitons coexisting with them. The second kind of asymmetry is the special case when one waveguide is linear, while the other one possesses quadratic nonlinearity. In contrast to the case when both waveguides are nonlinear, in this case the soliton solutions for the two limiting cases of closely and widely separated waveguides are not much different. All the solitons in this system are found to be stable. The obtained results, and especially bifurcations between solitons of different types, suggest straightforward applications to all-optical switching.

Evolution of N-body open clusters

Realistic n-body simulations of dynamical evolution of open clusters are discussed and compared with observations. Most of the models have 1000 bodies with initial masses following a power-law mass function of slope α = – 2.75 and mean mass 0.5 M⊙. Stellar evolution and mass loss are considered in detail. Neutron stars or white dwarfs (depending on the initial stellar mass) are generated by instantaneous changes in individual masses, when stars reach the end of their main sequence life. Close approaches between particles are treated by a two-body regularization technique that allows one to follow binary evolution in detail. Two types of tidal perturbation are considered: a smooth linearized galactic tidal field, simulated assuming that the clusters move in a circular orbit at 10 kpc from the galactic centre; and transient shocks, simulated by encounters with extended interstellar clouds of different mass spectrum, density and space concentration. Excellent agreement is found between the distribution of lifetime for galactic clusters and the life of the models. The combined action of evolutionary stellar mass loss and binaries (for clusters with 1000 bodies and a realistic mass function) is enough to arrest the core collapse. Tidal heating shapes the halo of the cluster and produces a distinctive density and velocity distribution. Encounters with standard clouds do not alter the life-time of the clusters; only giant molecular clouds produce a catastrophic disruption. Effects of mass segregation and preferential escape of light stars can account for the observed depletion of low luminosity stars in the better studied central region of clusters.

N-Body Simulations of Realistic Open Clusters

N-body simulations of dynamical evolution of open clusters have been computed with the purpose of comparing them with observations. Special effort has been put into reproducing conditions present in galactic clusters. Most of the models contain 1000 bodies with masses following a power-law mass function of slope a = −2.75 and mean mass 0.5M⊙. Neutron stars or white dwarfs (depending on the initial stellar mass) are generated by instantaneous changes in individual masses, when stars reach the end of their main sequence life. Close approaches between particles are treated by a two-body regularization technique that allows to follow binary evolution in detail. Two types of tidal perturbation are considered: a smooth linearized galactic tidal field is simulated assuming that the clusters move in a circular orbit at 10kpc from the galactic centre; transient shocks are simulated by encounters with extended interstellar clouds of different mass-spectrum, densities and space concentration. It is found that the combined action of evolutionary mass loss and binaries (when the cluster has a realistic mass function) is enough to arrest the core collapse. Tidal heating shapes the halo of the cluster. There is good agreement with the observed density and velocity distribution of open clusters and with reported changes in their mass function.