Dynamic Model Simulation Research Articles

Experimental investigation of abnormal transverse flow enhancement of α particles in heavy-ion collisions

The mass dependence of the transverse flow for $Z=1$--5 fragments from the collisions of $^{40}\mathrm{Ar}+^{27}\mathrm{Al}, ^{40}\mathrm{Ar}+^{48}\mathrm{Ti}$, and $^{40}\mathrm{Ar}+^{58}\mathrm{Ni}$ at 47 MeV/nucleon is investigated experimentally in this article. The transverse flow values are determined using the in-plane components of the fragment transverse momenta, where three conventional methods, i.e., the kinetic flow tensor method, the transverse momentum analysis method, and the azimuthal correlation method, are applied to reconstruct the reaction plane in an event-by-event basis. It is demonstrated from the comparison of the present experimental mass dependent flow measurements and the model simulations using an improved antisymmetrized molecular dynamics model that the experimentally observed abnormal $\ensuremath{\alpha}$ transverse flow enhancement is closely related to the reaction plane reconstruction procedure in the flow extraction. We further investigate the physical existence of the abnormal $\ensuremath{\alpha}$ flow behavior using a two-particle azimuthal correlation method, which allows us to provide the relative flow magnitude information with an identification of fragment charge number without the knowledge of the reaction plane differing from the three conventional methods. It is found that the relative flow magnitudes deduced from the two-particle azimuthal correlation functions with an identification of $Z$, with the correction for the recoil effect imposed by the momentum conservation, show a monotonically increasing trend as a function of fragment charge number, with no exception of the $\ensuremath{\alpha}$ flow enhancement. These results, in addition to those from the improved antisymmetrized molecular dynamics model simulations, definitely provide experimental evidences for the inexistence of the abnormal $\ensuremath{\alpha}$ flow behavior in the heavy-ion collisions at the present incident energy region in nature.

Modeling Dynamic System for Prediction of Dengue Hemorrhagic Fever in Maros District

BACKGROUND: Efforts to control the incidence of dengue hemorrhagic fever (DHF) have been carried out intensively, however, there is no significant reduction in the number of DHF sufferers. Meanwhile, the predictive model is expected to be an early warning to anticipate the incidence of DHF. AIM: Therefore, this study aims to determine the dynamic model for predicting dengue fever incidence in Maros Regency from 2020 to 2040. METHODS: This study used the research and development (R and D) method with a dynamic systems approach. The study was conducted in Maros Regency and the data on dengue cases in Maros Regency from 2014 to 2018 were used as samples. Meanwhile, interpretive structural modeling (ISM) was used to determine policy scenarios in reducing dengue cases while the analysis of the dynamic model of dengue fever was conducted using the Powersim program. RESULTS: The critical elements of DHF prevention in the Maros Regency include the Jumantik program, 3M Plus, early warning systems, and outreach. Furthermore, the prediction of the average incidence of dengue fever from 2020 to 2040 has decreased based on dynamic model simulations by applying the Jumantik scenario (46.8%), 3M Plus (61.17%), early warning systems (74.4%), counseling (52.12%), and the combined scenario (97.87%). CONCLUSIONS: The incidence of dengue fever in the Maros Regency is prevented and controlled by the combination of the Jumantik program, 3M Plus, early warning systems, and counseling.

A New Tool for Building Energy Optimization: First Round of Successful Dynamic Model Simulations

Several tools and pieces of software support building energy modelling for optimization, certification and comparisons of different scenarios and usages. Nevertheless, the consistent rise in accessible computational power and the expansion of ICT are pushing the development of new software functionalities and tools able to support cross-disciplinary work on smart building optimization. This paper introduces a new platform (under development) that combines the EnergyPlus dynamic simulation tool with extra-functionalities and pre-defined usage scenarios based on automatic actions to manage massive simulations and correlation analyses. The tool’s utility was tested in three experiments, with goals that we consider to be fundamental requirements: comparing simple retrofit actions to reduce net energy needs; analyzing the free-running potential of a demo building and the impacts of different low-energy technologies in terms of increasing thermal comfort (shading and ventilative cooling); and comparing measured sensor data indicators with simulated ones under real weather conditions for model verification. The results demonstrate the ability of the tool to automatically generate hundreds of EnergyPlus input building models by acting on building geometry; we focused on the most common uses for parametric dynamic simulations. Additionally, the way in which the tool combines the automatic modification of the building’s design and the parallel launching of multiple simulations allows the labor to be reduced. The user can execute complex tasks without spending any time working with model editing software and aggregating the results from multiple simulations.

Finding signatures of the nuclear symmetry energy in heavy-ion collisions with deep learning

A deep convolutional neural network (CNN) is developed to study symmetry energy (Esym(ρ)) effects by learning the mapping between the symmetry energy and the two-dimensional (transverse momentum and rapidity) distributions of protons and neutrons in heavy-ion collisions. Supervised training is performed with labeled data-set from the ultrarelativistic quantum molecular dynamics (UrQMD) model simulation. It is found that, by using proton spectra on event-by-event basis as input, the accuracy for classifying the soft and stiff Esym(ρ) is about 60% due to large event-by-event fluctuations, while by setting event-summed proton spectra as input, the classification accuracy increases to 98%. The accuracies for 5-label (5 different Esym(ρ)) classification task are about 58% and 72% by using proton and neutron spectra, respectively. For the regression task, the mean absolute errors (MAE) which measure the average magnitude of the absolute differences between the predicted and actual L (the slope parameter of Esym(ρ)) are about 20.4 and 14.8 MeV by using proton and neutron spectra, respectively. Fingerprints of the density-dependent nuclear symmetry energy on the transverse momentum and rapidity distributions of protons and neutrons can be identified by convolutional neural network algorithm.

Robust fuzzy stability control optimization by multi-objective for modular vehicle

Modular design becomes a trend in the automotive industry to increase competitiveness with vehicle platforms that combine multiple modules to provide different applications. This paper presents an optimized Fuzzy Logic Control (FLC) applied to modular all-wheel-drive vehicles, focusing on Electric Vehicles (EVs) and Hybrid Electric Vehicles (HEV) powered configurations. The vehicle behavior is determined by dynamic model simulation, in which the Magic Formula is applied to define the tire slip, associated with the load transfer during curves or drive/break situations. The controller acts as an electronic differential and changes the in-wheel motor torques to correct the vehicle trajectory during a standard maneuver. A multi-objective optimization based on the genetic algorithm determines the FLC configuration. The vehicle parameters (EV and HEV) have been modified to analyze the optimized FLC and, in all cases, the control showed an improvement in behavior to the vehicle without control. Finally, the FLC was implemented in a simple microcontroller and a hardware-in-the-loop simulation was developed to simulate a real vehicle operating condition and analyze this performance.

Influence of a damping parameter on helicity-independent all-optical switching.

Ultrafast magnetization switching has aroused much interest in recent years. Due to the complicated physical mechanisms, helicity-independent all-optical switching (HI-AOS) still lacks comprehensive understanding. In this article, we revealed the influence of damping on HI-AOS based on the simulation of the semiclassical atomic spin dynamics model. The results suggested that the smaller damping not only contributes to the increase to the maximum required pulse duration and the pulse fluence threshold for switching but also slows down the rate of magnetization dynamics. Our simulation results could provide some theoretical foundation to explore the optimization parameters of HI-AOS.

Analysis of Sub-Atmospheric Pressures during Emptying of an Irregular Pipeline without an Air Valve Using a 2D CFD Model

Studying sub-atmospheric pressure patterns in emptying pipeline systems is crucial because these processes could cause collapses depending on the installation conditions (the underground pipe covering height, type, fill, and pipeline stiffness class). Pipeline studies have focused more on filling than on emptying processes. This study presents an analysis of the following variables: air pocket pressure, water velocity, and water column length during the emptying of an irregular pipeline without an air valve by two-dimensional computational fluid dynamics (2D CFD) model simulation using the software OpenFOAM. The mathematical model predicts the experimental values of the study variables. Water velocity vectors are also analysed within the experimental facility, assessing the sensitivity of the drain valve to different openings and changes in water column length during the hydraulic phenomenon.

Research on the Differential Mechanisms of Knowledge Cross-Border Searching on Firms’ Dual Innovation in the Digital Context: Based on Simulation of System Dynamics Model

Acquiring and combining heterogeneous knowledge resources across organizational boundaries are an important path for the success of enterprises’ innovation. From the perspective of the relation attributes between knowledge elements, this paper divides knowledge cross-border searching into two types: domain knowledge searching and architectural knowledge coupling searching. Then, we construct a system dynamics model and use Vensim PLE software to carry out simulation analysis to explore the differential mechanisms of knowledge cross-border searching influence firms’ dual innovation in the context of digital transformation. The analysis results show that domain knowledge searching positively affects firms’ iterative innovation, while there is an inverted U-shaped relationship between architectural knowledge searching and firms’ disruptive innovation, indicating that different types of knowledge cross-border searching have differential effects on firms’ dual innovation. The simulation results also address that digital resources can promote enterprises' dual innovation in the process of knowledge cross-border searching. The research results reveal that the internal laws of knowledge cross-border searching affect enterprises' dual innovation in the context of digital transformation and provide a theoretical reference for enterprises to effectively use digital technology to adopt knowledge searching activities.

A novel, scalable, and modular bioreactor design for dynamic simulation of the digestive tract.

In vitro gut model systems permit the growth of gut microbes outside their natural habitat and are essential to the study of gut microbiota. Systems available today are limited by a lack of scalability and flexibility in the mode of operation. Here, we describe the development of a versatile bioreactor module that can be easily adjusted for culture size and capable of sensing and controlling of environmental parameters such as pH control of culture medium, rate of influx and efflux of the culture medium, and aerobic/anaerobic atmosphere. Bioreactor modules can be operated as single units or linked in series to construct a model of a digestive tract with multiple compartments to allow the growth of microbiota in vitro. We tested the growth of synthetic and natural bacterial communities in a multicompartment continuous dynamic culture model simulation of the mammalian gut. The distal compartments of a sterile system inoculated with the synthetic bacterial community at the proximal module attained a stable bacterial density by 24 h, and all the genera present in the inoculum were firmly established in the distal modules simulating the large intestine at 5 days of continuous culture. A natural bacterial community simultaneously inoculated into the distal modules attained a stable bacterial composition at the phylum level by Day 7 of continuous culture. The findings illustrate the utility of the system to culture mixed bacterial communities which can be used to study the collective biological activities of the cultured microbiota in the absence of host influence.

Design of the Active Control Algorithm to Reduction of the Vibrations due to Interaction High-Speed Railway Vehicle Bogie and Structure

This study analyzes excessive vibrations that occurred on the railway vehicle bogie with the computer simulation of a 4-DOF half car railway bogie dynamic physical model and Euler-Bernoulli flexible bridge beam with the simply supported boundary conditions has been introduced considering some limitations which affect problem formulation. To reduce these excessive vibrations other than conventional suspension systems such as passive one, an active suspension system has been designed and attached to the primary suspension system of the railway bogie car. Then, to control these active suspension systems, a control algorithm based on PID and SMC is considered. The coupled equation of motion of the railway bogie car and flexible Euler-Bernoulli bridge beam is obtained by Hamilton’s principle in the time domain with the active suspension system. Finally, to demonstrate the effect of the active suspension system with the PID and SMC algorithm upon these excessive vibrations, a computer simulation has been implemented, and the results are presented comparatively. Consequently, the maximum railway vehicle bogie vertical displacement and vertical acceleration have been significantly reduced.

Projected climatic changes lead to biome changes in areas of previously constant biome

AbstractAimRecent studies in southern Africa identified past biome stability as an important predictor of biodiversity. We aimed to assess the extent to which past biome stability predicts present global biodiversity patterns, and the extent to which projected climatic changes may lead to eventual biome changes in areas with constant past biome.LocationGlobal.TaxonSpermatophyta; terrestrial vertebrates.MethodsBiome constancy was assessed and mapped using results from 89 dynamic global vegetation model simulations, driven by outputs of palaeoclimate experiments spanning the past 140 ka. We tested the hypothesis that terrestrial vertebrate diversity is predicted by biome constancy. We also simulated potential future vegetation, and hence potential future biome patterns, and quantified and mapped the extent of projected eventual future biome change in areas of past constant biome.ResultsApproximately 11% of global ice‐free land had a constant biome since 140 ka. Apart from areas of constant Desert, many areas with constant biome support high species diversity. All terrestrial vertebrate groups show a strong positive relationship between biome constancy and vertebrate diversity in areas of greater diversity, but no relationship in less diverse areas. Climatic change projected by 2100 commits 46%–66% of global ice‐free land, and 34%–52% of areas of past constant biome (excluding areas of constant Desert) to eventual biome change.Main conclusionsPast biome stability strongly predicts vertebrate diversity in areas of higher diversity. Future climatic changes will lead to biome changes in many areas of past constant biome, with profound implications for biodiversity conservation. Some projected biome changes will result in substantial reductions in biospheric carbon sequestration and other ecosystem services.

Digestive behavior of unemulsified triglycerides with different chain lengths: In vitro dynamic and static simulated digestion models

Glyceryl tributyrate (GTB), glyceryl tridodecanoate (GTD) and glycerol tripalmitate (GTP) are typically short, medium and long-chain fatty acid glycerides, respectively. Their digestion behaviors play decisive roles in their health benefits. In this study, the digestion behaviors of unemulsified GTB, GTD and GTP were compared in the dynamic simulation digestion model (artificial gastric digestive system and semi-dynamic intestinal digestive system) and static simulation digestion model. In these two models, the digestibility is GTB > GTD > GTP. In the gastric phase, 4.5%–24.5% of triglycerides were hydrolyzed, and this phenomenon was more obvious in the dynamic model. In addition, the transition of digestive behaviors from the stomach to the intestine was smoother in the dynamic model. The particle size of GTB is usually smaller than those of GTD and GTP, and this difference was weakened in the dynamic model. The high melting point of GTD and GTP also hindered their binding with digestive enzymes in digestion. Our research filled the gaps in the study of the digestion behaviors of unemulsified triglycerides with different chain lengths in different models.

Dynamic Pore-Scale Modeling of Residual Trapping Following Imbibition in a Rough-walled Fracture

We present a new, fully dynamic pore-network modeling platform that is employed to conduct a systematic pore-scale study of capillary trapping under various two-phase flow conditions in a rough-walled fracture. The model rigorously solves for the fluid pressure fields, incorporates detailed descriptions of pore-scale fluid interface dynamics, and explicitly accounts for flow through wetting layers. This modeling platform further benefits from heavy parallelization and advanced domain decomposition techniques to achieve computational efficiency. We first build an equivalent pore network of a rough-walled Berea sandstone fracture using its high-resolution x-ray images. Next, to validate the dynamic model, primary drainage and imbibition simulations are conducted with fluid properties and boundary conditions matching their experimental counterparts. We show that the predicted two-phase fluid occupancy maps for both displacement processes agree well with those observed experimentally using x-ray computed tomography. Afterward, a comprehensive simulation study of flow patterns and capillary trapping during imbibition is performed under varying flow conditions, fluid properties, and initial saturations. The generated results provide significantly improved insights into the effects of wettability, gravity and viscous forces, and initial non-wetting (NW) phase saturation on the morphology and size distribution of the trapped NW phase clusters and the final residual NW phase saturation. By revealing the interplay among the capillary, buoyancy, and viscous forces, our results create a guideline on how the removal of NW phase from fractured media can be influenced by adjusting the operational settings. These findings have broad implications for predictions of capillary trapping behavior in fractured media.

Sustainability of religious communities.

This article focuses on the relationship between church population and sustainability. We carried out the study on a sample of Presbyterian churches in South Korea, and implemented dynamic optimization of the church population based on the Susceptible-Infected-Recovered (SIR) epidemic model. In particular, System Dynamics (SD) and Agent-Based Model (ABM) simulations are performed for a prototype model with key parameters that contribute to church growth. Potential parameters reflecting sustainability for churches trigger dramatic growth in church populations. We categorized five dimensions of sustainability with various multi-dimensional indicators in order to measure the level of sustainability, and we obtained the values of the indicators by analyzing a number of news articles searched with a text mining technique. As time-dependent values of sustainability are imposed on the generic SD model for church population dynamics as sustainable potential parameters, the optimized result reproduces specific features for the church population. We discuss the roles of key parameters for sustainable church growth, and the contributions of the churches to sustainability.

3-D Path Planning With Multiple Motions for a Gliding Robotic Dolphin

This paper presents a three-dimensional (3-D) path planning method that combines the gliding with dolphin-like motions for the gliding robotic dolphin. A specific task that the robot uses the gliding motion for long-distance cruise and the dolphin-like motion for maneuverable obstacle avoidance is employed. The results of simulations and aquatic experiments validate the full-state dynamic model and the specific task, further offer some theoretical supports for 3-D path planning. Further, the 3-D path planning method is composed of three main components: 1) gliding path generation; 2) improved Astar (A*) algorithm; and 3) segmented Bezier curve smoothing. First, the gliding path is generated autonomously with the kinematic constraints that are obtained via the simulations of dynamic model. Furthermore, when the obstacles are detected by the sonar, an improved A* algorithm is employed to avoid the obstacles. Afterward, considering the path planned by A* is unsmoothed, a segmented Bezier curve method is presented. Simulation results demonstrate the effectiveness of the method, offering valuable insight into the utilization of hybrid underwater robots in the context of real-time task execution.

Plantar fascia loading at different running speed: a dynamic finite element model prediction

Loads on the plantar fascia could be influenced by running speed and relate to its pathology. This study calculated and compared plantar fascia strains under different running speed conditions using a dynamic finite element foot model and computational simulations. The model was previously validated featuring twenty bones, bulk soft tissue, muscles/ligaments, and a solid part of plantar fascia. A runner performed running trials under one preferred speed (PS), two lower (PS - 10% and PS - 20%) and two higher (PS + 10% and PS + 20%) speed conditions. The movement data were processed to drive musculoskeletal modelling and calculated boundary/loading conditions for the subsequent finite element analyses. The results show that peak strains of the plantar fascia increased with increasing running speed. From PS – 20% to PS + 20%, peak strain in the proximal and distal fascia regions increased by 96.78% and 58.89% respectively. Running speed could directly affect plantar fascia loading, which should be considered in running regimens and rehabilitation programmes. However, prescribing speed control for runners is worth pondering as it influences the trade-off between maximum single-step loads and loading frequency, which in coalescence determine the risk of plantar fascia injury and warranted further investigations.

Simultaneously enhanced strength and ductility of TIG welds in Inconel 718 super-alloy via ultrasonic pulse current

Abstract This paper presents a novel self-induced ultrasonic arc welding (U-TIG) with high-efficient, which improves tensile strength and ductility of TIG welds in Inconel 718 super-alloy simultaneously. The effects of ultrasonic frequencies on arc shape, weld forming and weld penetration characteristics were systematically studied by high-speed camera and optical microscope. The characteristics of grains and precipitated phases in the weld metal were quantitatively analyzed by backscattered electron microscope, electron backscatter diffraction. The evolution models of grains refinement and reduction-dispersion with Laves phase were constructed based on molecular dynamics model and numerical simulation. The evolution diagrams of microstructures in tensile stretching revealed the mechanism of enhancing strength and ductility. Ultrasonic pulse current not only reduces and refines Laves phase, respectively by 81.8% and 52.2%, but refines grains (almost 33%) with higher orientation. The excellent distribution of the finest grains and Laves phase with dispersion is corresponding to ultrasonic frequency nearly 80 kHz, which benefits ductility enhancement of welds from 311% to 410%. Grains refinement leads to the increasing of grains boundary length and zigzag, meanwhile, the morphology of Laves phase changes from long-strip shape to refined pebble one, which is responsible for tensile strength improvement, closing to base metal of 92%.

COVID-19 Outbreak: Model-Driven Impact Analysis Comparing Oman and Pakistan

Motivated by the rapid spread of COVID-19 all across the globe, we haveperformed simulations of a system dynamic epidemic spread model in differentpossible situations. The simulation, not only captures the model dynamic of thespread of the virus, but also, takes care of population and mobility data. Themodel is calibrated based on epidemic data and events as they happened. Thesimulation results are quite disturbing, indicating that, during a process of stringent social distancing and testing strategies, a small perturbation can lead toquite undesirable outcomes. The simulation results, although consistent in expected outcomes across changing parameters’ values, also indicate a substantialmismatch with real numbers. An analysis of what can be the reason of this mismatch is also performed. Within these contradictions, a comparative analysisof COVID-19 outbreak between two geographically close but demographicallyvery different countries – that is Oman and Pakistan – is performed.

Experimental analysis on hydrodynamic coefficients of an underwater glider with spherical nose for dynamic modeling and motion simulation

In this paper, we present a study of an underwater glider with a cylindrical body, a conical end shape and a spherical nose with NACA0009 airfoil wings. In the experimental section, we investigate the hydrodynamic coefficients of drag and lift as well as the torque on the glider then analyze the launch velocity, launch angles, angular velocity, and displacement range as the main parameters for evaluating of motion dynamics. In the numerical section, we investigate the optimal performance of the glider using the meta-heuristic optimization method in order to find the path and range of motion of the moving mass and control of the sea glider, which is very important for navigation scope. To be specific, body and wings hydrodynamic coefficients are obtained in the velocity range of [0.2, 1] m/s; According to the results, the drag coefficient increases with increasing velocity, while the lift coefficient increases up to velocity of 0.8 m/s, then decreases at velocity of 1 m/s. Also, the wing drag coefficient decreases with increasing velocity, while the wing lift coefficient increases with increasing velocity. In the next step, in order to calculate an optimum ratio between obtained depth and horizontal distance, the designed algorithm investigate the glider launch angle and finally, the 10 degrees launch angle is chosen as the optimum angle. Subsequently, the analysis performed on mass center displacement range shows that the oscillation interval [- 0.045, 0.085] m is an optimum displacement domain.

Responses of vegetation greenness and carbon cycle to extreme droughts in China

Increasing drought stress under climate change exerting large impacts on vegetation has aroused growing concern, yet how vegetation greenness and carbon cycle respond to extreme drought is not well understood. In this paper, we studied this issue with various data sources including satellite observation, flux sites upscaling estimation, atmospheric inversion, and Dynamic Global Vegetation Model (DGVM) simulations over China during the period 2000–2015. We found a highly consistent negative response of greenness and carbon fluxes to extreme droughts, with the largest reduction in Gross Primary Productivity (GPP, a standardized anomaly of -1.26 ~ -0.33), a slightly smaller extent decrease of Net Ecosystem Productivity (NEP, -0.74 ~ -0.14) due to concurrent decrease of respiration, and reduced Leaf Area Index (LAI, -0.39 ~ -0.20). Besides, there was a large spatial heterogeneity across different regions and biomes, where Loess Plateau was one of the most vulnerable regions. The ambient climate conditions were found to modulate the drought response. Drought sensitivity of greenness and GPP peaked where mean annual temperature is around 25 °C, while that of NEP decreased along increasing precipitation gradients.