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Explosion is a significant threat to chemical process safety, which often occurs suddenly with a wide range of impact, resulting in catastrophic disasters. Predictions of explosion hazards are required for regional safety assessment and disaster resilience enhancement of chemical industrial parks (CIPs). This paper, therefore, aims to develop a conceptual framework for systematically analyzing explosion evolutions and quantifying the potential hazards by combining system-theoretic process analysis (STPA) method with numerical simulation. The proposed framework consists of 5 steps: (i) establishment of hierarchical safe control structures (SCSs) of important chemical processing zones in the CIP, (ii) computational fluid dynamics (CFD) modeling for potential explosion evolutions in each zone by changing the examined parameters randomly, (iii) development of a convolutional neural network (CNN) prediction model through constant self-learning of CFD pressure field data, (iv) comprehensive assessment of blast damage by incorporating the outputs of the above numerical models into existing evaluation methods, (v) identification of unsafety control actions and causes, and safety constraints for the improvement of SCSs. Provided with monitoring data, the developed analysis architecture can predict explosion process hazards and recommend appropriate safety strategies in real time. This would service the multi-level requirements for explosion prevention and protection, supporting better-informed decision-making. The paper describes the concepts and implementation process of the method as a first step. [ABSTRACT FROM AUTHOR]

Miniature ion trap mass spectrometer enables mass-to-charge ratio analysis of ions via quadrupole field in a low vacuum environment. It plays an important role in on-site detection due to its portability and specificity. In order to gain a deeper understanding of the analysis mechanism of miniature ion trap mass spectrometers, a quadrupole MS ion trajectory numerical simulation model (QITNS) is established in this paper for ions trajectory calculation under the action of quadrupole field, exciting field and neutral gas molecule collision. Compared with the existing methods, the model in this paper is simpler and more direct, which effectively explored the effects of dipole excitation and quadrupole excitation on ion manipulation under high background pressure. The simulation results demonstrate that high RF amplitude, low auxiliary AC amplitude and quadrupole excitation can effectively improve the isolation resolution. Besides, it clarified the difference between the analysis mechanism of ion trap mass spectrometers under high background pressure (above 13.332 Pa) and absolute vacuum conditions. The relevant results are consistent with the conclusions of previous experiments and other theories, proving the applicability and accuracy of the proposed calculation model and solution method. This research bears the guiding significance for further understanding the mechanism of quadrupole mass spectrometry as well as designing and developing miniature mass spectrometers. [Display omitted] • A simple numerical model is proposed for quadrupole mass spectrometry by directly coupling resonance and attenuation terms. • The model can elucidate the key factors for improving the resolution of the ion trap mass spectrometer. • It can also elucidate the ion manipulation rules under high background pressure conditions for miniaturized ion trap. [ABSTRACT FROM AUTHOR]

A system of diffusion–reaction equations coupled with a dissolution–precipitation model is discussed in this paper. We start by introducing a microscale model together with its homogenized version. In the present paper, we first derive the corrector results to justify the obtained theoretical results. Furthermore, we perform the numerical simulations to compare the outcome of the effective (homogenized) model with the original heterogeneous microscale model. [ABSTRACT FROM AUTHOR]

In this paper, two new climate change mathematical models are extended using the stochastic-deterministic piecewise hybrid fractional derivatives, where the hybrid fractional order operator is applied to extend the deterministic model and the fractional Brownian motion operator is applied to extend the stochastic model. The steady states analysis of the propsed models are discussed. Two numerical methods are constructed to study the behavior of the proposed models. These methods are Caputo proportional constant Adams-Bashfourth fifth step method for solving the hyprid fractional deterministic model and the modified nonstandard Euler Maruyama technique to study numerically the fractional Brownian motion stochastic model. Several numerical test examples are given to demonstrate the efficiency of the methods and to support the theoretical results. [ABSTRACT FROM AUTHOR]

In this paper, a fractional nonlinear control strategy based on the nested saturations technique and the Caputo-Fabrizio derivative for a quadrotor aircraft, to maintain desired position and orientation in stationary flight and trajectory tracking tasks, is proposed and developed. In addition, the dynamic model is obtained by using the Euler–Lagrange formulation, and then it is generalized to an arbitrary order through the Caputo-Fabrizio derivative. The traditional nonlinear control based on the nested saturation technique is also developed and implemented on the quadrotor for comparison purposes between both control schemes. Numerical simulations demonstrated the superiority of the proposed control strategy for stabilizing the quadrotor at hover and reaching the desired position and orientation, over its integer-order counterpart. In addition, three additional desired trajectories are considered, keeping the same gains and orders, to demonstrate the robustness of the proposed control scheme under different operating conditions. In this sense, our controller presents significant performance improvements, which were validated through system simulations. Our proposed control system and its traditional counterpart were tuned experimentally using the response of the system to a desired trajectory. [ABSTRACT FROM AUTHOR]

The National Aeronautics and Space Administration (NASA) is currently developing the next generation of spacesuits for use in future exploration missions. This effort, referred to as the Exploration Extravehicular Mobility Unit (xEMU), has been underway since 2015 with the goal of demonstrating the new technologies during a mission to the International Space Station (ISS). Due to the complexity of the xEMU system, and particularly its portable life support system (PLSS), computer simulations are heavily relied on in the development process, from dynamic loads analysis to software verification. The models of the physical systems that are currently being used for system-level simulations are mostly empirical, where the underlying formulas are mathematical fits to test or simulation data. An advantage of this approach is the fact that these models are very performant and can be used in real-time applications such as user interface testing and operator training. The research presented in this paper describes a different approach to modeling and simulation. A simulation tool focused on life support systems for human spaceflight in general and PLSSs in particular has been under development at the Technical University of Munich (TUM) since 2006. The spacesuit specific variant of this tool is called The Virtual Spacesuit (V-SUIT) and is now being utilized in the current spacesuit development process at the NASA Johnson Space Center (JSC). In contrast to the previously mentioned empirical models, V-SUIT uses a first-principles-based, bottom up modeling approach, where basic physical, chemical or biological effects are modeled at the lowest level and the component and system models are created using these fundamental building blocks. This enables the simulation to account for effects, and especially off-nominal situations, that may not be within the range of validity of the empirical models. This paper presents the structure of and the rationale behind V-SUIT itself as well as a status report on the ongoing effort to integrate it with the existing simulation systems in use at JSC, which is based on Trick/GUNNS. As a proof of concept, a single component model from V-SUIT, that of the spacesuit water membrane evaporator (SWME), has been integrated with NASA's simulation tool. Results include comparisons of the performance of the two simulation systems and a description of challenges that were encountered during implementation. The paper closes with an outlook towards the future developments that are planned for V-SUIT within the xEMU development program. • A novel approach to dynamic system-level simulations is applied to a spacesuit. • Multi-disciplinary, bottom-up modeling instead of domain-specific, top-down models. • Performance shown to be fast enough to provide value during system development. [ABSTRACT FROM AUTHOR]

Photovoltaic (PV) systems have become an integral and widespread part of renewable energy generation. In combination with energy storage, they offer a variety of advantages such as increased self-sufficiency or improved grid stability. However, geographic location, subsidies, energy tariffs, size of PV panels and battery, and other factors significantly influence the overall performance and profitability of the system. Solving this complex task of system design and component dimensioning is not easy. The diversity and multitude of parameters therefore usually requires the help of, more or less complex, computer simulations. This led and still leads to a high publication activity on techno-economic and other optimizations for such systems. However, the operating strategies and component models are often oversimplified, leading to results with significant errors. The goal of this paper is to provide in-depth insight into component modeling and parametrization for PV module, battery energy storage, and inverter, as well as giving suggestions on appropriate control strategies. The focus lies on the description of suitable simple-but-accurate models and their parametrization. In order to avoid the effort of having to conduct measurements for component characterization, an approach relying on values presented in product data sheets is considered. Furthermore, the effects of model simplifications, as they are found in many publications, are shown. Finally, the importance of an uncertainty analysis for the entire simulation is discussed in order to gain insight into the accuracy of the calculated simulation results and their dependency on model- and input-parameters. • Photovoltaic system modeling/simulation. • Component modeling for PV module, battery energy storage and inverter. • Suitable simple-but-accurate models and their parametrization • Characterization relying on product data sheets with minimal informations. [ABSTRACT FROM AUTHOR]

A composite contact algorithm for a complex particle system containing polyhedrons and super-ellipsoids is proposed in this paper to simulate the grinding process of ore in a ball mill. In this algorithm, the contacts between polyhedrons are calculated based on the overlapping volume method, and the contacts between super-ellipsoids are determined by a deepest point method. The contacts between super-ellipsoids and polyhedrons are obtained by transforming super-ellipsoids into polyhedrons, and then using the overlapping volume method between the polyhedrons. The increase in the number of faces of the super-ellipsoid contributes to the closer shape to the real shape. In this paper, experimental researches and numerical simulations are carried out to validate the accuracy of this composite contact algorithm. Furthermore, the influence of the ratio of super-ellipsoids and polyhedrons, the number of faces of converted super-ellipsoid, and the sharpness of the super-ellipsoid on the computational efficiency are compared in both box filling process and particles mixing process in a rotating tumbler. Finally, the stability and feasibility of this composite contact algorithm is tested in a ball mill application containing more particles. Unlabelled Image • A contact algorithm for polyhedron-super-ellipsoid particle system is proposed. • Experiments and numerical simulations are carried to validate this algorithm. • The computational efficiency of this composite contact algorithm is studied. • The stability and feasibility of this algorithm is tested in a ball mill application. [ABSTRACT FROM AUTHOR]

• The numerical model's setup for the steel fibre reinforced concrete (SFRC) segment. • Numerical simulations of GPR detection for SFRC segment under different conditions. • Optimum frequency selection of the SFRC segment. • Validation of an SFRC segment detection based on a model test. • Calculation of the equivalent relative dielectric constant (ERDC) of SFRC segments. The SFRC segment is gaining attention in shield tunnels due to their better mechanical properties. However, the existence of steel fibres poses a greater difficulty when attempting to utilize ground penetrating radar (GPR) for nondestructive quality inspection compared to conventional reinforced concrete segments. This paper presented a refined numerical model of SFRC segments with gprMax software, to investigate the penetration characteristics of GPR. The numerical model incorporated four different steel fibre contents, namely 0%, 0.5%, 2.5%, and 5%. The model also included an internal void and a surface metal plate to compare and analyze the waveform characteristics of GPR with the normal sections of the segment. The orthogonal test of numerical simulation investigates the imaging characteristics, power attenuation patterns, and imaging features of three different GPR frequency gradients: 200 MHz, 500 MHz, and 1000 MHz. This analysis helps in selecting the appropriate detection frequency based on the observed energy attenuation patterns and imaging characteristics. Then, the model test was conducted at the selected frequency to study the penetration performance of GPR. The research results indicate that the numerical model established in this paper demonstrates good effectiveness in studying the waveform characteristics of steel fibre-reinforced concrete under various conditions. The numerical model established in this paper realized the study of the penetration characteristics and imaging features of different steel fibre contents, GPR frequencies, and detection targets. Analysis of waveform characteristics, power attenuation, and imaging results indicates that GPR at 500 MHz exhibits better detection performance for SFRC segments. The results of the numerical simulation were verified through model tests of real SFRC segments, demonstrating that 500 MHz has good penetration performance for SFRC segments. This paper also proposed a calculation method for equivalent relative dielectric constant (ERDC) based on the model test results and validated its rationality through the analysis of numerical simulation results and real GPR waveforms. [ABSTRACT FROM AUTHOR]

Second-order macroscopic continuum models have been constantly improving for decades to reproduce the empirical observations. Recently, a series of experimental studies have suggested that the stochastic factors contribute significantly to destabilizing traffic flow. Nevertheless, the traffic flow stability of the stochastic second-order macroscopic continuum model has not received the attention it deserves in past studies. More importantly, we have found that the destabilizing aspect of stochasticity is still not correctly validated in the existing theoretical stability analysis. In this paper, we analytically study the impact of stochasticity on traffic flow stability for a general stochastic second-order macroscopic model by using the direct Lyapunov method. Numerical simulations have been carried out for different typical stochastic second-order macroscopic models. Our analytical stability analysis has been validated, and our methodology has been proved more efficient. Our study has theoretically revealed that the presence of stochasticity has a destabilizing effect in usual stochastic macroscopic models. • Stability condition of a general stochastic second-order macroscopic continuum model. • The Lyapunov method outperforms the eigenvalue method. • The stochastic macroscopic models respond differently to the presence of stochasticity. • The presence of stochasticity has a destabilizing effect in usual stochastic macroscopic models. [ABSTRACT FROM AUTHOR]

Highlights • Constitutive equations for a vertical rod bundle are reviewed. • Dependence of distribution parameter on flow conditions is discussed. • 1D momentum equation by considering void fraction distribution is discussed. • Effect of channel size on interfacial area concentration is discussed. Abstract In view of the quality assurance of two-phase flow simulations, CSAU (Code Scalability, Applicability, and Uncertainty) methodology and code V & V (Verification and Validation) have been proposed. The estimation of simulation uncertainty is indispensable in using best-estimate computational codes. A key of successful two-phase flow simulations is to use the state-of-the-art constitutive equations to close the mathematical system used in two-phase flow analyses. The advanced constitutive equations should be developed based on “physics” behind phenomena and should consider scaling parameters which enable their application beyond test conditions used for a code validation. Two-phase flow simulations in a rod bundle is important in various industrial apparatuses such as heat exchangers and nuclear reactors. Constitutive equations for two-phase flows in a vertical rod bundles have been advanced in recent five years. In view of this, this paper provides a comprehensive review of most advanced constitutive equations for two-phase flow analyses in a vertical rod bundle. The constitutive equations of two-phase flow parameters reviewed in this paper are flow regime map, void fraction, void fraction covariance and relative velocity covariance, interfacial area concentration and wall friction. In addition, an exact formulation of one-dimensional momentum equation in two-fluid model considering void fraction distribution is discussed. [ABSTRACT FROM AUTHOR]

• Comparison for the first time of FEM and RC in TEM transient simulation. • RC replicates results of FEM under steady state with deviations lower than 3 % • RC replicates also values, trends and rates of variation under transient conditions. • RC presents negligible computational cost. This paper demonstrates that resistance–capacitance models provide equal results than models based on finite-element software when predicting the performance of a thermoelectric module under transient-state conditions. Previous papers on this topic fall short as comparing finite-element models with simplified versions of resistance–capacitance models. It was confirmed that resistance–capacitance models replicate results of finite-element models in the simulation of a thermoelectric module under steady-state conditions. Deviations lower than 3 % in electric power and efficiency (ratio of electric power to heat input) are obtained for temperature differences between heat source and heat sink as large as 200 K. Similarly, deviations lower than 3 % are obtained for simulation of a thermoelectric module under transient-state conditions. Resistance-capacitance models not only replicate values, trends and rates of variation predicted by finite-element models under step, linear and sinewave variations in the boundary conditions, but they also do this with negligible computational cost. [ABSTRACT FROM AUTHOR]

Due to environmental and economic advantages, the production and utilization of renewable and eco-friendly fuels derived from residues have received attention globally. Gasification, a thermo-chemical waste valorisation method, is considered a flexible recycling method in terms of the employed feedstock, gasifier type, and the applications of the producer gas. Numerous operational parameters predominantly define the producer gas quality in conjunction with feedstock traits. As the defining parameters in a gasification process are interdependent and likely affect the process in a complex way, it is seemingly irrational to individually study the impacts of each variable and find an optimized operational condition experimentally. In this context, implementing mathematical and computer-based models is a pertinent strategy for accelerating research and developments in this field. Among all conceivable modelling approaches, thermodynamic equilibrium modelling is the most prevalent one, frequently adopted in various biomass gasification-related studies, but due to the consideration of several simplifying assumptions, particularly the equilibrium state condition, the reported deviations between experimental and modelling results are considerable. Various modification methods, such as restricted chemical equilibrium modelling, tar and char inclusion, use of modifying coefficients, and addition of heat dissipation factor, are proposed in thermodynamic modelling-based studies to enhance the modelling accuracy. Consequently, this paper aims chiefly to review all aspects of thermodynamic modelling and simulation, whether using stochiometric, non-stochiometric, or Aspen Plus modelling approaches, and to highlight the effectiveness of different modifications methods by considering the findings of studies conducted over the last decade to update the current knowledge concerning biomass gasification. • Gasification can contribute to solve the waste management issues and help meet the future energy needs. • Most studies on biomass gasification are based on thermodynamic equilibrium models. • Aspen Plus is a design tool and most prevalently employed simulator used for thermodynamic analysis. • Assumptions and simplification of problematic parameters, especially tar formation, reduce modelling accuracy. • Several modifications are proposed to enhance credibility of the thermodynamic-based models. [ABSTRACT FROM AUTHOR]

Road network microsimulation is computationally expensive, and existing state of the art commercial tools use task parallelism and coarse-grained data-parallelism for multi-core processors to achieve improved levels of performance. An alternative is to use Graphics Processing Units (GPUs) and fine-grained data parallelism. This paper describes a GPU accelerated agent based microsimulation model of a road network transport system. The performance for a procedurally generated grid network is evaluated against that of an equivalent multi-core CPU simulation. In order to utilise GPU architectures effectively the paper describes an approach for graph traversal of neighbouring information which is vital to providing high levels of computational performance. The graph traversal approach has been integrated within a GPU agent based simulation framework as a generalised message traversal technique for graph-based communication. Speed-ups of up to 43 ×  are demonstrated with increased performance scaling behaviour. Simulation of over half a million vehicles and nearly two million detectors at a rate of 25 ×  faster than real-time is obtained on a single GPU. [ABSTRACT FROM AUTHOR]

In this paper, a novel numerical simulation approach based on the finite element method for dynamically modeling the excavation process of shield tunneling is proposed, with the shield-ground interactions well captured. This method is capable of mimicking the alternating modes of advancing and stopping of a shield boring machine during underground construction, with the important effects of the cutterhead rotation and slurry support pressure considered. Under the cutting action, the soil at the excavation face would experience irreversible deformation and damage, such that additional support needs to be provided by the cutterhead blades and slurry to maintain stability. The impacts of key construction parameters are examined, including cutterhead rotary speed, advance rate, and slurry support pressure, on shield tunneling operations and ground responses. The numerical model is rigorously validated against physical model experiments. This work provides useful insights into the mechanistic processes in the stratum during shield tunneling, including the spatiotemporal evolution of ground deformation patterns and stress redistributions. The results offer valuable guidance for optimizing shield tunneling operations and enhancing tunneling safety and efficiency. [ABSTRACT FROM AUTHOR]

This paper aims to improve existing models for drag, lift, and pitching torque coefficients of cylindrical disc particles with a wider range of aspect ratios and particle Reynolds numbers. The full body-fitted direct numerical simulations (DNS) are carried out for three-dimensional flow past cylindrical discs in order to quantify the coefficients at aspect ratios from 0.2 to 0.6, incidence angles from 0°to 90°, and Reynolds numbers from 0.1 to 300. The CFD results are validated against the aerodynamic coefficients of both spherical and non-spherical particles presented in the literature. A full set of new correlations for the coefficients, dependent on aspect ratio, incidence angle, and Reynolds number, is further derived according to the CFD predicted data. The results show that the new correlations have a promising performance for the disc particles considered in this study. [Display omitted] • CFD simulations are performed for drag, lift, and pitching torque coefficients. • A complete set of correlations for C D , C L , and C T is proposed. • Proposed correlations work well outside the Stokes regime. • The correlation predictions agree with the CFD simulations. [ABSTRACT FROM AUTHOR]

This paper investigates the dynamic behavior of a Van der Pol oscillator (used as an archetypal self-sustained oscillator) coupled to a bistable nonlinear energy sink (BNES). We first show using numerical simulations that this system can undergo a multitude of motions including different types of periodic regimes and so-called strongly modulated responses (SMR) as well as chaotic regimes. We also show that a BNES can be much more efficient than a classical cubic NES but this is not robust since a little perturbation can switch the system from harmless to harmful situations. However, even in the most unfavorable cases, it is possible to find a set of parameters for which the BNES performs better than the NES. A multiple time scales approach is then addressed to analyze the system. In this context, we show that the so-called Multiple Scale/Harmonic Balance Method (MSHBM) must be modified (compared to its usual use) to consider the specific feature of the BNES, i.e., that it can have a nonzero-mean oscillating motion. This allows us to derive a so-called amplitude-phase modulation dynamics (APMD) which can reproduce the complex behavior of the initial system. Because of the presence of a small perturbation parameter (i.e., the mass ratio between the BNES and the VdP oscillator), the APMD is governed by two different time scales. More precisely, it appears as a (3,1)-fast–slow system whose motion is constituted in a succession of slow and fast epochs. Founding a (3,1)-fast–slow APMD is interesting since that implies a more complex dynamics than in the case of a classic NES whose APMD is only (2,1)-fast–slow. A fast–slow analysis is finally conducted within the framework of the geometric singular perturbation theory. From the computation of the so-called critical manifold and the analytical expressions of the APMD fixed points, a global stability analysis is performed. This enables us to interpret a certain number of regimes observed on numerical simulations of the initial system. • A Van der Pol oscillator is coupled to a Bistable Nonlinear Energy Sinks is studied. • The so-called MSHBM is modified to consider specific features of the BNES. • The obtained amplitude-phase modulation dynamics (APMD) is a (3,1)-fast–slow system. • Fast–slow analysis of the APMD is performed. • This enables to interpret a certain number of regimes observed on numerical simulations. [ABSTRACT FROM AUTHOR]

This paper deals with the usage of a toolkit Control Design & Simulation in development software LabVIEW for simulation of a two-position controller. This automatic control can be used to regulate regulation processes with high rise time such as temperature processes. Many of these processes can be categorized as second order systems. Main topic of this paper is the description of on-off controllers, their abilities and shortcomings and the way of use of such controllers to regulate processes of a second order. The publication then describes the development software LabVIEW, mainly useful toolbox Control Design & Simulation. This module was then used to design, simulate and optimize two-position controller. [ABSTRACT FROM AUTHOR]

In this paper, a novel sliding mode observer is proposed for systems that do not satisfy common conditions required for fault estimation, in particular the so-called matching condition and minimum phase condition. Other works attempt to circumvent the matching condition by using multiple observers in cascade, or higher order sliding modes, whilst the minimum phase condition can be relaxed at the cost of some faults and the states being not estimated, or the fault estimation being corrupted by the fault time derivative (or other dynamics). For the proposed scheme in this paper, only one observer is required, the minimum phase condition is relaxed to detectability, and the matching condition is greatly simplified to a condition related to the system dimensions which makes the scheme also applicable to the case where there are less outputs than faults. Finally, a simulation example is conducted to verify the effectiveness of the proposed observer. [ABSTRACT FROM AUTHOR]

Psychological factors affect the movement of people in the competitive or panic mode of evacuation, in which the density of pedestrians is relatively large and the distance among them is small. In this paper, a crowd is divided into groups according to their social relations to simulate the actual movement of crowd evacuation more realistically and increase the attractiveness of the group based on social force model. The force of group attraction is the synthesis of two forces; one is the attraction of the individuals generated by their social relations to gather, and the other is that of the group leader to the individuals within the group to ensure that the individuals follow the leader. The synthetic force determines the trajectory of individuals. The evacuation process is demonstrated using the improved social force model. In the improved social force model, the individuals with close social relations gradually present a closer and coordinated action while following the leader. In this paper, a grouping algorithm is proposed based on grid density and relationship via computer simulation to illustrate the features of the improved social force model. The definition of the parameters involved in the algorithm is given, and the effect of relational value on the grouping is tested. Reasonable numbers of grids and weights are selected. The effectiveness of the algorithm is shown through simulation experiments. A simulation platform is also established using the proposed grouping algorithm and the improved social force model for crowd evacuation simulation. [ABSTRACT FROM AUTHOR]

This paper addresses the problem of powered descent control of a lunar lander during its final landing phase, where soft and precise landing at the target cite is required. In the literature, this problem has been solved considering a fully actuated lunar lander. Recently, landers are designed as complex systems with several onboard payloads and subsystems for completing demanding mission tasks. There are increasing constraints on mass budget and space availability onboard a lander. In order to meet these requirements, a novel controller using a single thruster is proposed. The proposed controller has three control inputs (thrust and two gimbaled angles) to control the six degrees of motion of a lander; these control inputs are non-affine. The proposed controller is designed based on variable structure control technique augmented with a high order filter, an immersion and invariance-based mass estimator and a sliding mode angular velocity observer. The stability analysis using Lyapunov theory and the results of the numerical simulations along with Monte Carlo simulations of the system show that the precise landing of the lunar lander using a single thruster is feasible. • The position and attitude control of a lunar lander using a single thruster is examined. • A novel controller along with lander mass and angular velocity observers are designed. • The proposed controller is based on variable structure control technique. • The Lyapunov theory is applied to prove the stability of the proposed control scheme. • Results of numerical simulations show the feasibility of the proposed control scheme. [ABSTRACT FROM AUTHOR]

• The extremal ellipsoid surface reflecting the dynamic mechanism of the gyrostat system is derived. • The bifurcation of the Casimir power and energy leaps are found to be the indicators of different definitive dynamics. • The state changes of the displacement orbit of the gyrostat are simulated by the COMSOL finite element platform. Most of the existing research on gyrostat systems uses the Melnikov method to analyze chaotic dynamic characteristics. The mechanism of chaotic motion from the energy perspective of gyrostat systems has rarely been analyzed. The gyrostat system with positive damping disturbance is modeled in this paper. Casimir energy and power are given. The mechanism of the orbital expansion and contraction of the gyrostat is revealed through the sign change of Casimir power and the ellipsoid of Casimir energy. The bifurcations of the Casimir power corresponding to the state bifurcation and Lyapunov exponent spectrum reflect the evolution and transition of gyrostat's dynamics. The energy-level leap expressed by the variance of Casimir energy is found to determine the bifurcation of dynamics for the first time. The coexistence of the gyrostat is explained using Casimir power and local stability of equilibrium point. The COMSOL finite element simulation platform is built to study the state changes of the displacement orbit of the frame gyrostat model. A comparison is performed for the displacement results conducted by the COMSOL and the numerical simulation for the gyrostat system kinematic model. The different displacement states of the gyrostat system under free motion and in the presence of damping disturbance and external torques are obtained. [ABSTRACT FROM AUTHOR]

The subsea capping stack is crucial equipment for emergency rescue in a blowout scenario, which determines the success or failure of the emergency rescue. The secondary risk prevention of the blowout emergency continues to face a persistent challenge. This paper proposes a methodology framework for emergency risk of the subsea capping stack, which aims to realize the quantitative risk assessment of installation operation by integrating numerical simulation and an Artificial neural network (ANN) model. Herein, the numerical model of fluid impact for the capping stack is constructed, and the impact forces of the blowout fluid are analyzed. The calculation results indicate that the blowout pressure, water depth, and installation height significantly affect the impact force during emergency operations. Furthermore, a genetic algorithm optimizing the neural network (GA-BP) model for quickly predicting the blowout impact force is established to improve emergency response efficiency based on sufficient simulation data. The prediction model has a minor mean absolute percentage error (MAPE), and its accuracy is also verified compared with the SVM model. Besides, the developed model speeds up the processing time from hours to seconds compared to numerical simulation. Therefore, it can provide a decision-making basis for emergency engineers at the site of blowout accidents more efficiently. • An integrated methodology is proposed to quantify the installation risk for the subsea capping stack. • The simulation model of the capping stack during the installation process is constructed to predict the impact forces. • A prediction model is developed to speed up the processing time from hours to seconds compared to numerical simulation. [ABSTRACT FROM AUTHOR]

This paper analyzes the stability and passivity problems for a class of memristor-based fractional-order competitive neural networks (MBFOCNNs) by using Caputo's fractional derivation. Firstly, impulsive effects are taken well into account and effective analysis techniques are used to reflect the system's practically dynamic behavior. Secondly, by using the Lyapunov technique, some sufficient conditions are obtained by linear matrix inequalities (LMIs) to ensure the stability and passivity of the MBFOCNNs, which can be effectively solved by the LMI computational tool in MATLAB. Finally, two numerical models and their simulation results are given to illustrate the effectiveness of the proposed results. [ABSTRACT FROM AUTHOR]

• The DEM simulation modeling method for sunflower seed particles was proposed. • The optimum DEM parameters for the sunflower seed particle were determined. • Bulk density and repose angle of sunflower seed were investigated by EDEM. • A sunflower seed DEM model with simulation results close to the actual was found. • The results facilitated the improvement of the simulation accuracy. A modeling and simulation method was developed to comprehensively describe and build discrete element model for non-spherical particles based on the discrete element method (DEM). To popularize the application of sunflower seeds in computer digital simulation technology, the motion patterns and dynamic response characteristics of sunflower seeds in key processes such as sowing and harvesting are explored with the help of discrete element analysis methods to optimize the dimensional parameters and structural performance of related mechanical components. This paper takes edible sunflower seeds 1013 as the research object, and proposes a discrete element analysis model building method for individual sunflower seeds and groups of sunflower seeds particles by testing and analyzing the triaxial dimensions and three-dimensional volumes of sunflower seeds and the shape simplification of the seeds. 6 sunflower seed multi-sphere models (25 sub-spheres, 28 sub-spheres, 31 sub-spheres, 34 sub-spheres, 37 sub-spheres, 40 sub-spheres) with different accuracy and 2 sunflower seed polyhedral models (cuboid and triangle pyramid) with different shapes were established using the multi-sphere and polyhedron filling methods. The physical tests and angle of repose simulation tests were applied to measure and calibrate the intrinsic parameters and contact parameters of sunflower seeds. The physical test results of the bulk density and angle of repose are compared with the simulation test results to verify the feasibility of the discrete element modeling method for sunflower seeds proposed in this paper. The results show that the simulation results of bulk density and angle of repose are closer to the experimental results when the multi-sphere model is 31 sub-spheres and the polyhedral model is cuboid, considering fewer spheres and faster simulation rates. And the accuracy and applicability of the discrete element model and parameters of sunflower seeds are further verified through the simulation test of the productivity of the spiral conveying device of the 4ZXRKS-4 sunflower combine harvester test bed. [ABSTRACT FROM AUTHOR]

Construction planning takes place at many levels. This paper pertains to the level called lookahead planning, during which planners make their plan more realistic as construction tasks approach execution. To improve the quality of lookahead planning, the construction industry has benefited from implementing the Last Planner® System (LPS) that emphasizes creating reliable workflow. Successful lookahead planning relies on task anticipation by breaking down tasks to the level of operations, designing those operations, and making tasks ready by identifying and removing their constraints so that tasks can become executable assignments. This paper presents a study, using computer simulation, of the relationship between improving Task Anticipated (TA) in lookahead planning and overall project duration. The results indicate that increasing TA can have a positive influence on reducing project duration. The authors recommend that industry practitioners use the TA metric to gauge their planning performance and then to improve on it. [ABSTRACT FROM AUTHOR]

This paper presents an extensive examination of the wake characteristics and hydrodynamic performance of a 1:60 scale horizontal axis tidal stream turbine under yawed inflow conditions. Experimental investigations were conducted in a laboratory flume, while numerical simulations utilized the actuator line method and large-eddy simulation technique. The turbine was subjected to an inflow turbulence intensity of 6% and was tested at five different yaw angles (5°, 10°, 15°, 20°, and 30°). The findings demonstrate a substantial reduction in the power coefficient as the yaw angle increases, with a notable drop of 47.1% recorded at a yaw angle of 30°. Furthermore, numerical simulations of wake characteristics, including mean velocity and turbulence intensity, were examined and compared with measurements, yielding satisfactory agreement. The yawed wake flow exhibited asymmetrical distributions of mean velocity and deviations from the centerline. Additionally, distinct deformations of the yawed wake in the y - z cross sections were observed, indicating a discernible curled kidney shape that intensified with larger yaw angles. Moreover, interactions between the turbine wake and support structures affected the width and turbulence intensity of the near wake, introducing additional unsteadiness that accelerated wake recovery. • The impact of yaw on tidal turbine performance and wake behavior has been studied through water flume experiments and numerical simulations. • Power loss is observed under yawed inflow, with the maxiamun reduction of 47.1% at yaw angle of 30°. • The aggravation of wake deflection and the acceleration of velocity recovery are observed as yaw angle increases. • Yaw misalignment causes a curled kidney shaped profile in wake cross sections. • Blade tip vortices, nacelle wake, stanchion wake and their interactions severely affect the near wake characteristics. [ABSTRACT FROM AUTHOR]

[Display omitted] • Lattice beam model extended to self-healing in cementitious materials. • A new rate dependent discrete damage-healing model is presented. • Healing response derived from healing-agent chemo-physical properties. • Detailed information is provided on the size and disposition of cracking and healing zones throughout a transient analysis. • The model provides valuable information required for designing a self-healing system. • Model validated using experiments with healing under fixed and moving crack conditions. • Nature and extent of damage-healing zones determined numerically. This paper describes the development of a discrete lattice model for simulating structures formed from self-healing cementitious materials. In particular, a new approach is presented for simulating time dependent mechanical healing in lattice elements. The proposed formulation is designed to simulate the transient damage and healing behaviour of structures under a range of loading conditions. In addition, multiple and overlapping damage and healing events are considered. An illustrative example demonstrates the effects of varying the healing agent curing parameters on the computed mechanical response. The model is successfully validated using published experimental data from two series of tests on structural elements with an embedded autonomic self-healing system. The meso -scale model gives detailed information on the size and disposition of cracking and healing zones throughout an analysis time history. The model also provides an accurate means of determining the volume of healing agent required to achieve healing for all locations within a structural element. The importance of the information provided by the model for the design of self-healing cementitious material elements is highlighted. [ABSTRACT FROM AUTHOR]

In this paper, the chemotaxis partial differential equations models which describe the movement by one community in reaction to one chemical or biological signal are given and solved numerically on surfaces. The models and the numerical method concerned are in terms of a generic form of chemotaxis models. We develop a new semi-implicit finite element scheme based on the gradient and Laplacian recoveries to linearize the equations. Meanwhile, we modify the proposed semi-implicit scheme as a characteristic form and present a novel strategy for the discretization of characteristic derivative on surface. The lumped mass modification is employed for positivity preservation. And the related analysis results are provided. We investigate the accuracy and convergence of the proposed method by numerical tests. And the simulations of blowing-up solution, pattern formulations and aggregations of bacteria demonstrate the applicability of the proposed methods. [ABSTRACT FROM AUTHOR]

Abstract Considering that network community might have a profound effect on the cascading failure of R&D network, we generate the weighted scale-free R&D network and quantify the network community through network modularity Q. Afterwards, we propose the cascading failure model of R&D network based on SIR-CA model, and analyze the special effects on the cascading failure of R&D network through numerical simulation. The simulation results show that network modularity Q has a U-shaped effect on the robustness of R&D network, there is a negative correlation between the delay effect and the robustness of R&D network. Additionally, we verify that overlapping firms have more significant influence than those firms with the same degree and K-shell on the robustness of R&D network. This paper reveals the law of cascading failure of R&D network considering the network community, which is of practical significance to enhance the robustness of R&D network, and enrich the theory of dynamics of the network community. Highlights • The cascading failure model of R&D network based on the SIR-CA model. • The impact of community structure on the cascading failure of R&D network. • The effect of the delay effect on the cascading failure of R&D network. • The effect of overlapping firms on the cascading failure of R&D network. [ABSTRACT FROM AUTHOR]

Abstract Antarctic krill (Euphausia superba) is one of the most abundant commercial species in the world and still has great potential for further development and utilization. It is, however, very important that the resource is utilized in a sustainable manner in terms of efficiency and selectivity, which can be enhanced through proper design of pelagic trawls that are used for harvesting the species. Pelagic trawls rely heavily on hydrodynamic forces acting on the netting to form desirable shapes. It is thus crucial to understand hydrodynamic forces acting on the trawl to predict its performance. A large Antarctic krill trawl with a net opening circumference of 200 m was designed for a fishing vessel (2855 kW) and analyzed by numerical simulation and physical model tests. A numerical model of Antarctic krill trawl was established based on the finite element method. The principle of minimum potential energy was employed to determine the equilibrium configuration and the tension distribution of the trawl in a uniform current. The Newton–Raphson method was applied to solve the equilibrium equation. A series of physical model tests were conducted in a flume tank to verify the result from numerical simulation. The results showed that the trawl with a net opening circumference of 200 m had superior hydrodynamic performance and could be well matched with fishing vessels of the class for the efficient production of Antarctic krill. This paper demonstrates the use of scientific methods for the design of large Antarctic krill trawls and the application of numerical simulation to study the hydrodynamic performance. Highlights • A new Antarctic krill trawl is designed. • Study on hydrodynamic performance of the Antarctic krill trawl. • Verifying the accuracy of numerical simulation. • Calculation of shape and tension distribution. [ABSTRACT FROM AUTHOR]

Highlights • A life‐cycle maintenance cost analysis method for fault diagnosis is proposed. • Time‐dependent false and missed alarms in fault diagnosis are considered. • A false and missed alarm weight optimization method is proposed. • A life‐cycle maintenance cost is minimized with the proposed methods. Abstract Fault diagnosis aims to diagnose system failures and to enable timely maintenance that, in turn, can minimize system maintenance costs. In order to evaluate and maximize the benefits from fault diagnosis, the life‐cycle maintenance cost should be analyzed. This paper presents a framework for life‐cycle maintenance cost analysis that considers time‐dependent false and missed alarms in fault diagnosis. First, time‐dependent false and missed alarms are proposed. The false and missed alarm rates are not static but vary depending on the health state of the engineered system, which changes over time. Second, a life‐cycle maintenance cost analysis framework is proposed. This is based upon a stochastic simulation method that can incorporate time‐dependent false and missed alarm rates and various uncertainties, such as health degradation and health restoration through maintenance. Third, a fault diagnosis model design method is proposed, based upon the proposed life‐cycle maintenance cost analysis framework. The proposed method incorporates optimal false and missed alarm weights into the life‐cycle maintenance cost. As a result, the proposed ideas enable accurate estimation and minimization of the overall life‐cycle maintenance cost. The effectiveness of the proposed methods is demonstrated via a numerical example and an electro‐hydrostatic actuator case study. [ABSTRACT FROM AUTHOR]

Abstract Manufacturing machinery is becoming increasingly complicated, and machinery breakdowns not only reduce efficiency, but also pose safety hazards. Due to the needs for maintaining high reliability within facility operation, various methods for condition monitoring are suggested as the importance of maintenance has increased. Among the various prognostics and health management (PHM) techniques, this paper introduces a model-based fault detection and isolation (FDI) technique for the diagnosis of machine health conditions. The proposed approach identifies faults by extracting fault signal information such as the magnitude or shape of the fault based on a defined relationship between a fault signal and observer theory. To validate the proposed method, a numerical simulation is conducted to demonstrate its fault detection and identification capabilities in various situations. The proposed method and data-driven methods are then compared with regard to their fault diagnosis performance. [ABSTRACT FROM AUTHOR]

Highlights • Two different vibration suppression schemes are presented and compared. • The vibration suppression schemes are incorporated into model construction. • The proposed controller can tolerate its own uncertainties that randomly occur. • Simulations provide some technical basis for a more economical choice in practice. Abstract This paper addresses the attitude stabilization and vibration suppression problem for flexible spacecraft subject to model parameter uncertainty, controller perturbations, external disturbances and input constraints. The attitude model of flexible spacecraft is described and converted into a state space form in terms of passive and active vibration suppression schemes. A novel state feedback controller is proposed based on the exactly available expectation of a new variable, which is introduced to model a randomly occurring controller gain perturbation. Based on Lyapunov stability theory, sufficient conditions for the existence of the nonfragile H ∞ controller considering input constraints are given based on linear matrix inequalities (LMIs) in terms of additive perturbation and multiplicative perturbation. Then, the developed controller subject to required constraints can be obtained, where the nonfragile property is fully considered to improve the tolerance to uncertainties in the controller. Numerical simulations are performed to demonstrate the effectiveness and superiority of the proposed control strategy in attitude stabilization and vibration suppression, where it should be noted that the passive vibration suppression scheme is superior for high natural frequencies while the active vibration suppression scheme is superior for low natural frequencies. Moreover, the low natural frequencies have more influence on the performance of attitude stabilization and vibration suppression. [ABSTRACT FROM AUTHOR]

Abstract A developed numerical simulation technique for buffeting longitudinal wind forces on rectangular buildings is presented in this paper. This technique mainly aims to generate time histories with prescribed probabilistic characteristics for the longitudinal wind load turbulent component which is considered as a zero mean stationary multivariate one-dimensional stochastic process, then the instantaneous wind load time histories are obtained by adding each mean wind load component to the corresponding generated time history of the turbulent component. A simplified procedure, which takes the advantage of aerodynamic admittance function, is proposed to estimate the longitudinal wind load on buildings in the frequency domain. A very efficient simulation algorithm based on spectral representation method which depends on superposition of trigonometric functions with random phase angles is used to perform the transformation from the frequency domain to the time domain. A MATLAB function is coded to implement the proposed simulation technique. By testing the proposed technique statistically, it has been noted that there are good agreements between the temporal and target auto/cross-correlation functions of the simulated wind forces, and by testing it structurally, the generated instantaneous wind load time histories show a good ability in giving a reasonable dynamic response for the studied building. [ABSTRACT FROM AUTHOR]

Highlights • The SCESVB configuration specimen proposed in this paper has the function to arrest crack propagation. • The reflected compressive stress wave confine the outgoing crack propagation. • The angle of V-shaped bottom of SCESVB specimens has effect on crack arrest function. • Propagation toughness is not an independent concrete parameter, and it is related to crack speed. Abstract Concrete structures usually contain cracks or microcracks. Under dynamic loading, such as impacts, blasts and earthquakes, these cracks may initiate and propagate, weakening concrete strength and structure's stability. It is thus necessary to carry out the research on the crack dynamic fracture behavior and to develop crack arresting technique for cracked concrete structures under dynamic loads. In this study, impact tests were performed using a drop-weight impact device. A single crack emanating from a semicircle and a V-shaped bottom (SCESVB) specimen was proposed. The V-shaped bottom has the function of arrest on the propagation of the pre-crack. Crack propagation gauges (CPGs) were used to measure crack propagation parameters. Three angles 120°, 150° and 180° were designed for the V-shaped bottom of the SCESVB specimens. The crack propagation behavior was simulated by the finite difference code AUTODYN, and the dynamic stress intensity factor (DSIF) was calculated by the finite element code ABAQUS. The critical DSIF was determined by the crack initiation time and the propagation time measured by the CPG. The experimental and numerical simulation results show that the SCESVB specimen is suited to studying crack propagation behavior and crack arresting behavior for concrete under dynamic loads. During the crack propagation process, the crack may arrest in a short time, and the critical DSIF at initiation is higher than that at propagation for the concrete. [ABSTRACT FROM AUTHOR]

Abstract We show in this paper how strain engineering alters the fundamental characteristic of a martensitic transformation (MT) and gives it a new set of properties including large quasi-linear elastic strain response with nearly vanishing hysteresis and low elastic modulus. The work is motivated and inspired by a recent experimental study on elastic and inelastic (transformation) strain matching in a pre-strained nano-composite with Nb nanowires embedded in a NiTi shape memory alloy matrix. In particular, we demonstrate by computer simulation that dislocations at Nb/NiTi interfaces produced by the pre-straining are responsible for the unprecedented properties. Microstructural evolution captured in the simulations reveals that local stress fields associated with the dislocations regulate the nucleation and growth of martensite, turning the otherwise sharp, strong first-order transition into a continuous, high-order like transition. The simulations predict that the stress-strain hysteresis and modulus of the composite decrease with increasing amount of pre-strain, which agrees well with the experimental measurement. This study suggests a design strategy by introducing non-uniform stress fields for enhanced properties of shape memory alloys. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Abstract As one of the most common obstacles in milling process, regenerative chatter will result in lessened productivity, poorer product surface finish and decreased cutting life of the tool. In order to suppress chatter, the spindle speed variation (SSV) has been proposed and researched for a long time. However, the previous researches mainly focus on the basic waveform variation, such as sine, cosine, square and triangular waveforms and didn't consider the effect of phase on milling stability, which weren't suitable to the complex and high spindle speed milling conditions. Based on the previous studies, this paper proposes the concept of multi harmonic spindle speed variation (MHSSV) including the phase factor for chatter suppression. The dynamic equations with MHSSV are derived to describe the milling process. Due to the existence of the milling period and the speed variation period, the least common multiple of these two periods is adopted as the Floquet period in semi-discretization method (SDM) for stability analysis. Because the speed variation function can be described by some finite parameters, the genetic algorithm is used to optimize these parameters in order to suppress chatter more effectively. As a result, the optimized milling process has higher stability limits, especially in the high speed zone, which validates the effectiveness of the multi harmonic spindle speed variation. In addition, the numerical simulation of milling process is implemented and verifies the correctness of the proposed method. Highlights • The dynamic equations with multi harmonic spindle speed variation including are derived to describe the milling process. • The stability analysis method based on semi-discretization is derived. • The speed variation is described by finite parameters and the genetic algorithm is used for parameters optimization. • The numerical simulation of milling process is implemented and verifies the correctness of the proposed method. [ABSTRACT FROM AUTHOR]

Abstract STRIM (Statistical Test Rule Induction Method) has been proposed as a method to effectively induce if–then rules from the decision table, and its effectiveness has been confirmed by simulation experiments. The method was studied independently of the conventional rough sets methods. This paper summarizes the basic notion of the conventional rule induction methods and newly formulates the idea of STRIM, and then considers the relationship between STRIM and conventional methods, especially VPRS (Variable Precision Rough Set), and shows that STRIM develops the notion of VPRS into a statistical principle. In a simulation experiment, we also consider the condition that STRIM induces the true rules specified in advance. On the other hand, real-world datasets are often small and/or contain missing and contaminated values in the decision table from various reasons. In order to apply STRIM to real-world datasets, we examine the capacity of STRIM in such circumstances by a simulation experiment, after studying the question of what size dataset is required for STRIM. Such studies and examinations are very important to confirm if STRIM is properly applied to real-world datasets, and the results are reasonable. Graphical abstract Highlights • The rule induction by STRIM and the conventional Rough Sets, particularly, VPRS. • The relationships and differences between them. • The superiority of STRIM to the conventional methods at various points. [ABSTRACT FROM AUTHOR]

This paper focuses mainly on the system design and performance analysis of the landmark-based INS/Vision Navigation System (INS/VNS). Firstly, the state and observation equations of the landmark-based INS/VNS are established. Secondly, the observability of the landmark-based INS/VNS with different number of landmarks is analyzed according to the rank of observability matrix. And Kalman Filter (KF) is designed for the landmark-based INS/VNS to estimate the errors of the navigation parameters for Unmanned Aerial Vehicle (UAV). Finally, the performance of the landmark-based INS/VNS is analyzed and compared with that of the landmark-based IMU/Vision Navigation System (IMU/VNS) via simulations. [ABSTRACT FROM AUTHOR]

Recently, the market promotion of wireless power transfer (WPT) products has generated great expectations for systematic design and optimization of practical WPT system (especially the coupler). The existing optimization methods usually employ the Finite Element Analysis (FEA) to simulate the magnetic field, where the effects and requirements of overall circuit are neglected. To address this issue, an optimization approach for the coupler based on circuit simulation is proposed in this paper, and the secondary compensation capacitor is further optimized to improve the system performance. The simulation model is embedded into Simulink and the calculation part is embedded into MATLAB, where the objective is to achieve the maximum efficiency by searching three variables under adequate constraints. The numerical results imply that the proposed method is more effective and accurate than the traditional trial-and-error way, and that it suits the practical WPT system design excellently. [ABSTRACT FROM AUTHOR]

This paper focuses on the problem of weak stabilization, strong stabilization and optimal control for a class of semilinear systems with distributed delay in a Hilbert space. We propose new family of feedback controls to discuss the weak and strong stabilization of this class of equations. Sufficient conditions for weak and strong stabilization are investigated as well. Moreover, we show that one of the used family of feedback controls is the unique solution of an appropriate minimization problem. Furthermore, some results in finite dimension are given. The obtained results are illustrated by an examples with numerical simulations for physical systems with distributed delay. [ABSTRACT FROM AUTHOR]

In order to facilitate the replacement of damaged components and prevent the weak-story mechanism of frame structure after strong earthquakes, a novel assembled self-centering buckling-restrained brace (ASC-BRB) is proposed in this paper. The proposed bracing system is comprised of the buckling-restrained brace (BRB) system and the self-centering (SC) system. The SC system consists of two sets of steel strands and one group of disc springs stacked in series to achieve the goal of large deformability and post-hardening behavior. The detailed configuration, fundamental working mechanism, and restoring force model of the ASC-BRB are first presented. Different from SC systems with bilinear elastic behavior of existing SC-BRBs, the SC system of ASC-BRB exhibits trilinear elastic behavior due to its special configuration. Then, quasi-static tests are conducted to validate the effectiveness of the proposed ASC-BRB. The experimental results indicate that the ASC-BRB has a flag-shaped hysteretic response with excellent self-centering capability, stable energy dissipation capability, and appreciable deformation capacity with a maximum ductility coefficient of 25.58. More importantly, the specimen can exhibit the anticipated post-hardening behavior. The refined numerical model of ASC-BRB is established and verified by the experimental results, which can effectively analyze the mechanical behavior of the main components of ASC-BRB, making up for the deficiency of the tests. According to the problems discovered in the tests and numerical analyses, an improved configuration of the ASC-BRB is proposed and validated by the numerical simulation of the BRB system before and after improvement. The numerical results indicate that the improved BRB system exhibits more stable hysteretic behavior, and the stress levels of the inner and outer tubes become much lower after replacing 1-shaped cores with steel angle cores. • An innovative assembled self-centering buckling restrained brace (ASC-BRB) with high post-yield stiffness was proposed. • Experimental results indicated that the proposed ASC-BRB exhibited stable hysteretic behavior, appreciable self-centering capability, large deformability, and prominent post-hardening behavior. • The theoretical restoring force model of the ASC-BRB coincided well with the experimental hysteretic curve. • The refined numerical model could effectively analyze the mechanical behavior of the main components of the ASC-BRB. • An improved configuration of the ASC-BRB was proposed and validated by the numerical simulation. [ABSTRACT FROM AUTHOR]

In this paper, the authors presented a concept of a construction of a parametric model of barely visible impact damage (BVID) in carbon fiber-reinforced composite structures based on a reconstruction of X-ray computed tomography scans, ultrasonic B- and C-Scans as well as numerical simulations of such a type of impact loading. Considering the results of the experimental tests made it possible to model the resulting BVID with a realistic geometry and the location of delaminations, while the results of the numerical simulations allowed confirming and adjusting the damage extent. The original procedure of the BVID reconstruction from non-destructive testing data was developed and presented in the paper for the purpose of preparing the parametric computer-aided design (CAD) models. Using both numerical and experimental results the generic shapes of BVID for the set of various impact energies and various impactors were achieved. The determined dependencies of changing the damage extent with respect to various energies and impactors made it possible to parametrize BVID. The resulting generic models of BVID were validated on the X-ray computed tomography scans. [ABSTRACT FROM AUTHOR]

Safeguarding and type approval of automated vehicles is a key enabler for their market launch in our complex traffic environment. Scenario-based testing by means of computer simulation is becoming increasingly important to cope with the enormous complexity and effort. However, there is a huge gap when assessing the safety of the virtual vehicle while the real vehicle will drive on the road. Simulation must be accompanied by model validation to ensure its credibility since errors and uncertainties are inherent in every model. Unfortunately, this is rarely addressed in the current literature. In this paper, a modular process is presented covering both model validation and safeguarding. It is characterized by the fact that it quantifies a large number of errors and uncertainties, represents them in the form of an error model, and ultimately integrates them into the safeguarding results. It is applied to a type-approval regulation for the lane-keeping behavior of a vehicle under various scenario conditions. The paper contains a thorough validation of the methodology itself by comparing its results with actual ground truth values. For this comparison, a binary classifier and confusion matrices are used that relate the binary type-approval decisions. The classifier demonstrates that the methodology of this paper identifies a systematic error of the simulation model across several safeguarding scenarios. Finally, the paper provides recommendations for alternative configurations of the modular methodology depending on different requirements. • Comprehensive overview about the validation of systems simulations. • Modular VV&UQ framework with aggregation of model errors and uncertainties. • First application of a VV&UQ approach to automated vehicles. • Detailed validation of a deterministic and a non-deterministic VV&UQ methodology. [ABSTRACT FROM AUTHOR]

In this paper, the robust consensus problem of fractional-order multi-agent systems with input saturation and external disturbances is studied under a directed fixed topology. It’s the first time to consider the fractional-order agent subject to input saturation. When there exist input saturation and external disturbances simultaneously, by means of the Mittag–Leffler stability theorem and low gain feedback technique, a control protocol is presented to guarantee the robust consensus can be achieved. Moreover, as a special case, the leader-following consensus can be achieved when there only exists input saturation. Finally, the results are verified by several simulation examples. [ABSTRACT FROM AUTHOR]

Industrials have an intensive use of numerical simulations in order to avoid physical testing and to speed up the design stages of their products. The numerical testing is indeed quicker to set-up, less expensive, and supplies a lot of information about the system under study. Moreover, it can be much closer to the physical tests as the computation power increases. Despite the rise of this power, time consuming simulations remain challenging to be used in design process, especially in an optimization study. Crash simulations belong to this category. These rapid dynamic computations are used by RENAULT during the sizing of the vehicle structure in order to ensure that it meets specifications set up to reach safety criteria in case of accidents. They are completed using finite element software such as VPS (Virtual Performance Solver) developed by ESI group that will be used in this study. For car manufacturers, the goal of the optimization study is to minimize the mass of the vehicle (and thus its consumption) by modifying the thicknesses of some parts (from 20 to 100 variables). Industrials such as RENAULT currently perform optimization studies based on numerical design of experiments. The number of computations required by this technique is from 3 to 10 times the number of variables. This is too much in order to be intensively used in a design process. In order to decrease the time-to-market and to explore alternative technical solutions, we explore the potential of using a parametrized reduced order model in the optimization studies. The parametrized reduced order model gives an estimation of the high-fidelity result for a new set of parameters without using the solver, by analysing the existing results of previous computations with various sets of parameters. The developed reduced order model is called ReCUR. It is partly based on a CUR approach embedded in a regression analysis. The regression statistical model uses the data of a few calculations made with the solver. Other tools such as clustering and linear programming are used to get the regression analysis more efficient. It is hoped to drastically reduce the number of required simulations of a standard optimization study. In this paper, the construction of the reduced order model will be presented. Then, the relevancy of using the reduced order model into a design process will be exhibited through the treatment of two industrial test-cases. Some improvements of the method as well as several potential uses will then be outlined. The applications will highlight the promising power of the method to shorten design process using optimization and long-run simulations. [ABSTRACT FROM AUTHOR]

Synthetic population is a key input to agent-based urban/transportation microsimulation models. The objective of population synthesis is to reproduce the underlying statistical properties of real population based on available microsamples and marginal distributions. However, characterizing the joint associations among a large set of attributes is challenging because of the curse of dimensionality, in particular when attributes are organized in a hierarchical household-individual structure. In this paper, we use a hierarchical mixture model to characterize the joint distribution of both household and individual attributes. Based on this model, we propose a framework of generating representative household structures in population synthesis. The framework integrates three models: (1) probabilistic tensor factorization, (2) multilevel latent class model, and (3) rejection sampling. With this framework, one can generalize not only the associations of within- and cross-level attributes, but also reproduce structural relationships among household members (e.g., husband-wife). As a case study, we implement this framework based on the household interview travel survey (HITS) data of Singapore, and then use the inferred model to generate a synthetic population pool. This model demonstrates great potential in reproducing the underlying statistical distribution of real population. The generated synthetic population can serve as a replacement for census in developing agent-based models, with privacy and confidentiality being protected and preserved. [ABSTRACT FROM AUTHOR]

This paper addresses a novel economic model predictive control (MPC) formulation based on a periodicity constraint to achieve an optimal periodic operation for discrete-time linear systems. The proposed control strategy does not rely on forcing the terminal state by means of a terminal equality constraint and hence it does not require a priori knowledge of a periodic steady trajectory. Instead, at each sampling time step the economic cost function is optimized based on a periodicity constraint over all the periodic trajectories that include the current state. The recursive feasibility and the closed-loop convergence to a periodic steady trajectory are discussed. Moreover, an optimality certificate of this steady trajectory is provided based on the Karush–Kuhn–Tucker (KKT) optimality conditions. Finally, an application to a well-known water distribution network benchmark is presented to demonstrate the proposed economic MPC in which the closed-loop simulation results obtained with a linear model and a virtual–reality simulator are both provided. [ABSTRACT FROM AUTHOR]

Rumor spreading has a profound influence on people’s well-being and social stability. There are many factors influencing rumor spreading. In this paper, we recommended an assumption that among the common mass there are three attitudes towards rumors: to like rumor spreading, to dislike rumor spreading, and to be hesitant (or neutral) to rumor spreading. Based on such an assumption, a Susceptible–Hesitating–Affected–Resistant(SHAR) model is established, which considered individuals’ different attitudes towards rumor spreading. We also analyzed the local and global stability of rumor-free equilibrium and rumor-existence equilibrium, calculated the basic reproduction number of our model. With numerical simulations, we illustrated the effect of parameter changes on rumor spreading, analyzing the parameter sensitivity of the model. The results of the theoretical analysis and numerical simulations illustrated the conclusions of this study. People having different attitudes towards rumors may play different roles in the process of rumor spreading. It was surprising to find, in our research, that people who hesitate to spread rumors have a positive effect on the spread of rumors. [ABSTRACT FROM AUTHOR]