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Hydrothermal treatment of sludge within the pulp and paper industry can have a wide range of possible reactor solid loads for different sludge types. The objectives of this work were to determine the effect of reactor temperature and solid load on the properties of sludge hydrochar and to simulate hydrothermal treatment of sludge within a pulp and paper mill. Laboratory experiments were first performed within reactor temperature and solid load ranges of 180–260 °C and 10–50%, respectively, and the effects of sludge treatment were determined by comparing parallel mill-scale simulations. Based on the results, both reactor temperature and solid load had a statistically significant effect on the solid, ash, carbon and energy yields of sludge hydrochar. Increasing solid load minimized carbon dissolution to the liquid phase and increased the solid and energy yield of the attained hydrochar. According to mill-scale simulations in a 9 m 3 batch reactor, treating primary sludge alone produced an energy surplus of 22–36 GJ through char incineration, decreasing to 12–22 GJ and 3.4–9.1 GJ for mixed and secondary sludge, respectively. Mixing primary and secondary sludge reduced the overall energy surplus by 2–8% compared with treating the sludge streams separately in two reactors. [ABSTRACT FROM AUTHOR]

Abstract A number of problems associated with dimensional stability of paper products have to do with hygroexpansion in response to changes in humidity or moisture content. The main underlying mechanism of hygroexpansion in paper is the effect of the change of fiber cross-sections transferred through fiber bonds. In fact, the transverse expansion of fibers can be an order of magnitude greater than the longitudinal expansion. Addressing such problems using modeling on the microscale is associated with large computational costs since both the bonds and the fibers need to be resolved. We present a method for modeling the hygro or thermal expansion of interconnected fiber networks modeled with beam elements and connected through beam-to-beam contact. Being a line structure, beams can only support pointwise contact, which poses a challenge for modeling the force transfer induced by the deformation of the cross-sections at the contact point. The idea of implementing the stress transfer is to use a concurrent multiscale approach in which the bond level is resolved in detail using the configuration of the fibers and the computed strains are passed over to the beam elements. We verify and prove the applicability of this approach by comparing it with continuum models. We demonstrate the advantage of using this approach in terms of its tremendous saving in time. The use of beam models for modeling the hygro- or thermal expansion of fiber networks enables considering relevant sizes in the problems involving dimensional stability, in particular those associated with embedded inhomogeneities. We will show the applicability of the model by providing insights into published experimental observations on the hygroexpansion properties of paper products. Finally, we will demonstrate that the use of a 2D model to simulate the inter-fiber bonds in a network, not only leads to underestimation of out-of-plane deformations, but also to overestimation of the contribution of the transverse deformation of fibers to the in-plane dimensional change of the network. [ABSTRACT FROM AUTHOR]

In this study, a computer model based on discrete element method is employed to simulate the unsteady state heat transfer from the fuser roll to the toner and coating layer during the Xerography printing of coated papers. The model coating layers consisted of randomly arranged spherical pigment and latex particles with commercially relevant size distributions. Effects of coating characteristics, toner size, multiple toner layers, toner melting energy, toner thermal conductivity, coating layer thermal conductivity, and fuser roll temperature and pressure were investigated. Iso-thermal contours of fusing time were generated to demonstrate the relative importance of different fusing conditions and toner properties. Simulation results showed that temperature variation highly depended on the toner size, toner melting energy and the fuser roll temperature. Moreover, simultaneous coupling of the compressive stress and heat transfer indicated that the pressure exerted by the fuser roll did not significantly affect the rate of heat transfer. [Copyright &y& Elsevier]

Thin-walled tubular deployable composite boom (DCB) has gained significant attention due to its lightweight, simple structure and high packaging efficiency. The experimental and numerical simulation methods were employed in this paper to investigate the folding behavior of the DCB. Using T700/epoxy unidirectional reinforced prepreg as raw material, DCB specimens were prepared by the vacuum bag method. To complete the folding experiments of DCB specimens, a folding mechanism was designed and manufactured. Folding experiments of DCB specimens were conducted and folding moment versus rotational displacement curves were measured. In addition, a Finite Element Model (FEM) was established to predict the folding behavior of the DCB. Different failure criteria were considered in the numerical analysis, including the Tsai‐Hill criterion and maximum stress criterion. Prediction results using the FEM were compared with experimental results, and both sets of results were in good agreement. It is shown that the DCB can achieve the folding function without failure. The research results in this paper are of great significance to the practical engineering application of the DCB. [Display omitted] • Six tubular deployable composite boom specimens and a precise folding mechanism were designed and prepared. • Folding experiments were conducted to measure the folding moment and rotational displacement curves. • A finite element model for predicting the folding behavior of the tubular deployable composite boom was established. [ABSTRACT FROM AUTHOR]

Abstract: A detailed mathematical process integration model of a pulp and paper mill in the Northern Sweden has been developed. The main objective of this work has been set to describe the practical development of the model with particular emphasis on the development of the digester and evaporation plant sub-models. Actual plant measurements have been used to validate the model. By implementing the sub-models into the complete plant model, the influence of different operation parameters on the overall plant performance has been investigated. Furthermore, introductory studies with the main objective to minimize the plant energy cost have been carried out. [Copyright &y& Elsevier]

Abstract: In this paper, the prospect of integrating a combined paper&pulp mill with fuel production via biomass gasification was investigated. In the study, three different types of gasifiers (circulating fluidised bed, entrained flow and indirect gasification) and three fuel processes (dimethyl ether, methanol and Fischer-Tropsch wax synthesis) were investigated using computer simulations. The paper reports differences from the stand-alone cases and the integrated cases, using the electricity equivalence efficiency as a measure. Only 6 out of the 18 integrated cases studied displayed a positive result from integration and no obvious fuel selection that stand out as the most beneficial one, however the synthesis of dimethyl ether is, in combination with all gasifiers assessed a rather good choice, with an change in efficiency from integration ranging from −1% to 4%. Dimethyl ether is not the best choice if the electrical equivalence is to be maximised however. In this case the combination of circulating fluidised bed gasification and methanol synthesis should be pursued. The production of Fischer-Tropsch wax should according to the chosen measure not be produced; however there is an added value in the production of a non-oxygenated fuel which has not been taken into account in this particular study. All cases leads to a reduction of 0.4–0.9 kg CO2 per kg of dry biomass used in the process for fuel synthesis and the possibility to export bark is a more significant factor in this respect than which type of fuel is synthesised. [Copyright &y& Elsevier]

Abstract: Effects of suction pressure and permeability on the steam heating characteristics of the wet paper are studied. Experimental results show that suction pressure enhances the energy absorption in the wet paper and effects of suction pressure strongly appear in the high-permeability paper, and also absorbed energy rate is decreased with increasing in heating time. From the numerical simulation results it is found that increase in moisture content and decrease of pressure gradient reduce the absorbed energy rate. Dimensionless numbers are derived from the basic equations to summarize the experimental and numerical simulation results. [Copyright &y& Elsevier]

In the present comment, the results of recently published by Li Shu and Yonglin Ju "Numerical Study on the Condensation Characteristics of Various Refrigerants Outside a Horizontal Plain Tube at Low Temperatures" in International Journal of Thermal Sciences 2022 are discussed. It is shown that one of the conclusions of the work that "at low saturation temperatures, the periodic-averaged heat transfer coefficient in the numerical simulation is lower than that calculated with Nusselt's equation, especially at large wall subcooling", is not supported by the results of simulation performed by the author of this comment. [ABSTRACT FROM AUTHOR]

This paper employs a numerical approach to investigate the impact of liquidity shocks on European options in modeling markets. To accurately capture the behavior of European options under liquidity shocks, a coupled system of differential equations is employed, consisting of a degenerate parabolic equation and a diffusion-free equation. The primary focus is on developing and analyzing implicit-explicit methods for numerically simulating European option pricing, specifically considering the presence of liquidity shocks while ensuring the positivity of the solution. The paper also includes convergence analysis and establishes the discrete comparison principle for the developed methods. Numerical experiments are conducted using both uniform and nonuniform meshes to validate the theoretical findings, demonstrating the efficiency and accuracy of the proposed methods. [ABSTRACT FROM AUTHOR]

Abstract: In the present work a number of configurations and difficulties of MEE system such as condensate flashing, vapor bleeding, steam splitting, preheating of liquor using condensate, variable physical properties and boiling point rise are taken into consideration to analyze the evaporation system. For this purpose seven effect evaporator system of a typical Indian pulp and paper industry is considered. The model developed is a set of nonlinear algebraic equations that include total and solute mass balances, energy balances, heat transfer rate equations, and the composition and temperature dependence of thermodynamic properties such as vapor pressures and enthalpies. The model is solved using nonlinear equation solver. Economic evaluation to optimize the number of flash tanks is carried out for seven effect evaporator system. The two different types of configurations of vapor bleeding are considered and compared. Considering optimum number of flash tanks and best configuration of vapor bleeding, a system is designed. Further, a modified system is found considering optimum number of flash tanks and preheating of liquor using condensate. This modified design enhances the steam economy by 23.77% and reduces the steam consumption by 36.76% in comparison to base case and thus, it is selected as optimum design. Finally, Pinch analysis of the MEE network has also been carried out and it is found that predicted results are compared well with base case. [Copyright &y& Elsevier]

Particle swarm optimization (PSO) is a widely adopted, rapid, efficient, and computer-friendly technique for optimization in various fields, including computer science, engineering, and mathematical modelling. In this paper, the nonlinear Schrodinger (NLS) equation has been solved numerically, which leads to soliton-type solutions, by utilizing the "Exponential cubic B-spline differential quadrature method (Expo-MCB-DQM) with PSO". The exponential cubic B-spline basis functions involve a parameter that must be assigned a value to find the numerical solutions. Until now, the value of a parameter had been determined by the hit-and-trial approach, which leads to unstable results. By employing the PSO technique, the optimal value of the parameter is determined, which enhances the accuracy of the numerical solutions. This study introduces an innovative combination of Expo-MCB-DQM with PSO, which is an innovative combination that optimizes the parameters in the basis function, leading to improved outcomes. To validate the authenticity and effectiveness of this methodology, it has been applied to two problems to present the numerical results in comparison with the exact solution. Additionally, the paper provides insightful discussions on the significant application of the NLS equation in optical fiber communication. [ABSTRACT FROM AUTHOR]

• Numerically investigate folding pattern and rigid-flexible coupled dynamics of satellite-sphere system. • Achieve a larger volume folding rate by pattern of inflatable sphere with orderly deployment. • Inflating process has great influence on satellite based on rigid-flexible coupled dynamic model. • Reduce influence by heavier satellite, small inflation rate and appropriate control torque. Inflatable spheres can be applied to the aerodynamic drag deorbiting device for satellites. It may bring about a complicated dynamic problem under the disturbance from the lightweight large-volume inflatable sphere to the satellite. In order to explore this problem, rigid-flexible coupled dynamics behaviors of satellite-sphere system during inflating process are numerically studied in this paper. The folding pattern of inflatable sphere is designed to obtain the parametric model in the folded state. The dynamic analysis model of this system is established to analyze dynamic behaviors, including the dynamics of the satellite-sphere system, the gas state of the airbag and the disturbance to the satellite, during the inflating process. Parameter effects on the attitude disturbance are studied. The results show that the satellite mass, inflating mass rate and control torque have a great impact on the attitude disturbance. These works provide theoretical bases and technical supports for the engineering development of inflatable sphere deorbiting devices. [ABSTRACT FROM AUTHOR]

On-orbit capturing is a crucial step in the application of dual-arm space robots, aiming to accurately grasp a moving target and avoid damage to the arms terminal parts (i.e. the end effectors) due to contact force saturation. This paper presents a synthetic control method with target sticking for on-orbit capturing using a dual-arm space robot system from the approaching phase to pre-grasping phase. In the approaching phase, an online trajectory planning method based on visual servoing is proposed to obtain the desired trajectories for end effectors in work space. Then the joint torques are designed by the inverse kinematics and inverse dynamics to track the desired trajectories. Different from most of the current research, a new sticking phase is proposed after the approaching phase and before the pre-grasping phase. In the sticking phase, a force and motion control method is designed to maintain a close relative distance between end effectors and the target, which can avoid saturation of contact forces and avoid damage to the end effectors. In what follows, an impedance control method is proposed in the pre-grasping phase to absorb the impact energy and grasp the target accurately. The synthetic control strategy integrates the controllers of all the phases mentioned above. Automatic switching among the phases is realized by using logic judgment according to the system real states, which is more consistent with the real capturing environment. Finally, numerical simulation results demonstrate the effectiveness of the proposed synthetic control scheme. The results can be applied to the trajectory planning and control of on-orbit capturing, avoiding contact force saturation and ensuring the safety of the system. [ABSTRACT FROM AUTHOR]

The paper concentrates on the issue of distributed disturbance observer-based nonfragile bipartite consensus within nonlinear delayed multiagent systems, encompassing both leaderless and leader-following structures. The delays under consideration are nonuniform, manifesting in the state, the nonlinearity, and the communication processes. To suppress the external disturbances and the observer gain perturbations, distributed nonfragile disturbance observers pertaining to relative output and communication delays are developed to estimate the external disturbances for each agent. Employing the developed disturbance observer, distributed control protocols for nonfragile bipartite consensus are constructed incorporating states, estimated disturbances, and communication delays. These protocols can ensure bipartite consensus, compensate for external disturbances, and tolerate uncertainties in control gain. New augmented Lyapunov-Krasovskii functions are formulated by introducing the triple integral term and the augmented vector. The new bipartite consensus criteria for the studied multiagent systems are established with less conservatism by employing the techniques on second-order Bessel-Legendre integral inequality, reciprocally convex combination, and free weight matrix. Finally, numerical simulations and comparisons are performed for both leaderless and leader-following scenarios, thereby validating and enhancing the theoretical outcomes. • Multiagent systems with nonlinearity, disturbance and multiple delay, is considered. • Both cooperative and antagonistic relationships are all considered in consensus. • The perturbations in both observer and bipartite consensus protocol. • New Lyapunov-Krasovskii functions, and Bessel-Legendre inequality are employed. [ABSTRACT FROM AUTHOR]

Advancements in bulk metallic glass thermoplastic forming unleash the potential to fabricate microscale metallic features with unparalleled precision and durability, i.e. microspine gripping structures for mobility platforms on planetary or in-space robots. Four designs of grippers were fabricated and rigorously tested. Coefficient of friction on four test surfaces were measured and compared to SiC paper and Velcro. The hardness and elasticity of the bulk metallic glasses make them a game-changer in the field, offering a superior alternative to conventional nonmetallic grippers. • Microspine grippers were manufactured via thermoplastic forming of bulk metallic glasses using silicon-on-insulator molds. • The microspines excelled on textured surfaces, where sharp points anchor on to pores or softer regions. • Mechanical behavior of microspines were studied using nanoindentor-based micro-compression and computer simulations. [ABSTRACT FROM AUTHOR]

• The infeasibility of the fuel-optimal powered landing problem is analyzed. • A maximum-thrust regulation strategy is proposed to reduce infeasibility. • A trajectory-tracking method with a disturbance compensator is proposed. • The disturbance compensator requires only the current state information. Convex optimization has great potential for onboard trajectory generation which can eliminate large state deviations and improve landing precision. In practical applications, the convex optimization problem is often infeasible under disturbances. In this paper, we analyze the reason for the infeasibility of the fuel-optimal trajectory optimization problem. The analysis result shows that the thrust saturation degrade the anti-disturbance performance and then lead to infeasibility. Based on this analysis, we improved the anti-disturbance performance of convex optimization-based guidance from two aspects: (1) a maximum-thrust regulation strategy is embedded into the original fuel-optimal problem to avoid thrust saturation; (2) a trajectory tracking method with a disturbance compensator is performed to attenuate disturbance effects and to make the initial state of each optimization cycle close to the existing feasible trajectory. Numerical simulations demonstrate that the proposed method can improve the infeasibility and can realize the high-precision landing under disturbances. [ABSTRACT FROM AUTHOR]

In this research paper, we delve into the analysis of a generalized discrete reaction-diffusion system. Our study begins with the discretization of a generalized reaction-diffusion model, achieved through second-order and L 1-difference approximations. We explore the local stability of its unique solution, both in the absence and presence of the diffusion term. To determine the conditions for global asymptotic stability of the steady-state solution, we employ suitable techniques including the direct Lyapunov method. To illustrate the practical application of this theoretical framework, we provide several numerical simulations that examine both the Lengyel-Epstein reaction-diffusion model and the discrete Degn-Harrison reaction-diffusion model. These simulations serve to validate the predictions of asymptotic stability. [ABSTRACT FROM AUTHOR]

In this paper, we propose a failure-informed multi-stage training algorithm for approximating the double-valley dark soliton solutions of the three-component nonlinear Schrödinger equation (NLSE). Although the physics-informed neural network (PINN) method has achieved remarkable results in many equations, it is ineffective when directly applied to the considered equation due to the non-vanishing background of dark solitons and the complexity of the multi-valley structure. To improve the approximation ability of the PINN, the algorithm we proposed generates effective samples adaptively based on Gaussian mixture distribution by combining the time-adaptive strategy, failure-informed enrichment technique, and pre-fixed technique. Furthermore, the algorithm is extended to learn the solution operator of three-component NLSE within a specialized solution space. The results of numerical simulation demonstrate that the improved algorithm has better approximation ability and faster convergence rate in approximating the solution and solution operator of the considered equation while using a smaller training set. • We explore a deep learning method for solving three-component nonlinear Schrödinger equation. • We proposed an improved PINNS by time-adaptive strategy, failure-informed enrichment technique, and pre-fixed technique. • The data-driven double-valley dark soliton solutions are derived by the proposed method. • The proposed method can be easily extended to the physics-informed DeepONets. [ABSTRACT FROM AUTHOR]

During autonomous rendezvous and docking (AR&D) with a tumbling target, multiple unfavorable engineering constraints exist, such as constraints on the control, velocity, or collision avoidance. Meanwhile, many sources of uncertainty exist, including incomplete and inaccurate measurements, control deviation, dynamic uncertainty, and inertial parameter uncertainty of the tumbling target, which significantly complicate the design of the guidance and control algorithm. Considering these challenges, this paper proposes a robust identification, planning, and control unified framework for AR&D with a tumbling target, which incorporates an extended Kalman filter (EKF) with a robust tube-based model predictive control for tracking (TMPT) controller. First, the EKF is designed to estimate the system state and inertial parameters of the target and then predict the future behavior of the tumbling target. Additionally, the prediction information of the target is transmitted to the designed TMPT controller as a reference signal. This TMPT controller unites trajectory planning and control in a single layer that can ensure the stability and recursive feasibility of the algorithm with a short prediction horizon. Moreover, it can guarantee that the closed-loop system is robustly and asymptotically convergent to the reachable set whose center is the optimal reachable periodic trajectory concerning the docking port of the tumbling target. The unified framework represents a robustness-to-optimality control strategy that can accomplish the AR&D mission efficiently while considering multiple engineering constraints and uncertainties. Finally, the efficiency of the proposed control framework is verified through a numerical simulation. [ABSTRACT FROM AUTHOR]

This paper addresses some classes of combined and separate imputation methods (CSIMs) of the population mean under stratified simple random sampling (SSRS) along with their characteristics. To the best of our knowledge, these imputation methods (IMs) have yet not been studied by any author under SSRS, hence these IMs are called 'novel'. In addition, the existing CSIMs are distinguished as the members of the suggested CSIMs, respectively. The theoretical conditions under which the proposed IMs perform better are obtained by comparing the proposed IMs with the existing IMs. To validate the theoretical findings, the numerical and simulation studies are conducted on real and artificial populations, respectively. [ABSTRACT FROM AUTHOR]

In this paper, a distributed bearing-based formation control scheme with finite-time convergency is proposed for multiple underactuated surface vessels (USVs). By virtue of the guide point-based model transformation method, the dimension of underactuated tracking error dynamics can be reduced from three to two. This allows us to convert the actuator model to a fully form that matches dimension-reduced tracking error dynamics. Further, to reduce the computation complexity, a finite-time recruited filter is designed according to first-order Levant differentiator. At meanwhile, auxiliary error compensation signals are introduced to address unknowns stemming from filter process and system dynamics. Since merely relative-distances and inner bearings are utilized in the proposed bearing-based formation approaches, the proposed control scheme provides a feasible solution to achieve formation control under body-fixed frame. Finally, theoretical analysis and numerical simulations are presented to demonstrate the efficacy. • Bearing-based finite-time formation control. • Underactuated surface vessels. • Levant differentiator. • Command filtered backstepping with error compensation signals and compensated errors. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel fractional-order hyperchaotic system is investigated. • Existence of chaotic attractors just in the fractional-order case, in this system, are reported. • Bifurcation diagrams and corresponding Lyapunov spectrum are computed. • The work reports the first example that shows existence of chaotic attractors that exist only in fractional-order case. Studying chaotic dynamics in fractional- and integer-order dynamical systems has let researchers understand and predict the mechanisms of related non-linear phenomena. Phase transitions between the fractional- and integer-order cases is one of the main problems that have been extensively examined by scientists, economists, and engineers. This paper reports the existence of chaotic attractors that exist only in the fractional-order case when using the specific selection of parameter values in a new hyperchaotic (Matouk's) system. This paper discusses stability analysis of the steady-state solutions, existence of hidden chaotic attractors and self-excited chaotic attractors. The results are supported by computing basin sets of attractions, bifurcation diagrams and the Lyapunov exponent spectrum. These tools verify the existence of chaotic dynamics in the fractional-order case; however, the corresponding integer-order counterpart exhibits quasi-periodic dynamics when using the same choice of initial conditions and parameter set. Projective synchronization via non-linear controllers is also achieved between drive and response states of the hidden chaotic attractors of the fractional Matouk's system. Dynamical analysis and computer simulation results verify that the chaotic attractors exist only in the fractional-order case when using the specific selection of parameter values in the Matouk's hyperchaotic system. An example of the existence of hidden and self-excited chaotic attractors that appears only in the fractional-order case is discussed. So, the obtained results give the first example that shows chaotic states are not necessarily transmitted between fractional- and integer-order dynamical systems when using a specific selection of parameter values. Chaos synchronization using the hidden attractors' manifolds provides new challenges in chaos-based applications to technology and industrial fields. [ABSTRACT FROM AUTHOR]

The processes occurring in near and far space have a significant impact on the safety of space flights. Processes such as explosions of supernovae and relativistic jets have a particularly great impact. They arise in quasars, black holes, protostars. Often such structures are observed during the formation of new stars. Such jets have a great impact on the safety of space flights. For example, there is currently no radiation shelter on the International Space Station, so astronauts are at serious risk of getting radiation sickness. In addition, the skin of the orbital station modules consists of aluminum, which accumulates secondary radiation. The formation process of new star systems is the result of complex processes that occur in interstellar gas. These processes include nonlinear interactions of turbulence, gravity, collisions of molecular clouds with each other, as well as rotation and several other factors. The evolution of the formation of superdense substance begins from the moment when it gathers in turbulent flows or is formed by supersonic collisions of molecular clouds with each other, or are formed during the intereaction of molecular clouds with supersonic waves, which are formed during the explosions of supernovae, until the moment when these superdense areas reach the prestellar density. Further, depending on several factors, these superdense formations either collapse or disintegrate and return to the interstellar medium. The analysis of observations allows to conclude that a significant part of the molecular clouds is not gravitationally bound. These conclusions are made based on the virial theorem, which expresses the connection between gravitational and kinetic energy. In this paper, a simulation of large molecular clouds collision in a three-dimensional formulation on ultra-high-resolution grids is carried out. Execution of such calculations requires a lot of computer capacity. The paper presents the results of computer modeling of large-scale processes of filament formation and superdense, gravitationally coupled structurally parallel computation clusters with hybrid architecture. Parallel simulation on supercomputers was conducted with author's software, which uses a modified second-order Godunov method of accuracy of the Total Variation Diminishion type. Calculations were conducted on grids that contain more than one billion cells (1024 × 1024 × 1024). The gravitational potential is calculated on graphic processors. To refine the calculations, the method of adaptive refinement of the AMR grid is used. Simulation results are presented for cases of frontal collision of two molecular clouds, which density is distributed along the radius according to certain laws. • The processes of formation of new stellar systems are studied in this work in 3D simulation. • Appearance of clumps and filaments is discussed. • Morphing of high compression clumps set in possible stars formation zone is discussed. • The calculation program is based on a modified scheme of a high order of accuracy. [ABSTRACT FROM AUTHOR]

This paper investigates the asteroid hovering problem using the Multiple-Overlapping-Horizon Multiple-Model Predictive Control method. The effectiveness of the predictive controllers in satisfying control constraints and minimizing the required control effort is making Model Predictive Control a desirable control method for asteroid exploration missions which consist of the asteroid hovering phase. However, the computational burden of Model Predictive Control is an obstacle to employing the asteroid's complex gravitational field model. As an alternative option, the Multiple Horizon Multiple-Model Predictive Control method has been introduced previously, which could provide a solution with the less computational burden with respect to the nonlinear Model Predictive Control. It was shown that it is not necessary to deduce the exact dynamics model to predict the system's behavior during a long period using this approach. However, the calculated control acceleration was not smooth enough because of the crisp borders of consecutive horizons, which may cause an image motion and degrades the geometric accuracy of high-resolution images in asteroid hovering missions. In this paper, the Multiple-Overlapping-Horizon Multiple-Model Predictive Control method is introduced instead to solve the problem of controlling acceleration fluctuations by overlapping consecutive horizons. Numerical simulation results are presented to validate the effectiveness of the proposed control method, and its advantage is demonstrated accordingly for the asteroid hovering problem in achieving the hovering position and velocity. [ABSTRACT FROM AUTHOR]

The distributed H ∞ consensus problem for heterogeneous multi-agent systems with nonconvex constraints is investigated in this paper. To deal with the coexistence of nonconvex constraints and disturbances, our main analysis is to transform the original system into a reduced-order system so as to use the H ∞ control theory to show the achievement of consensus with a desired H ∞ performance while the inputs of all agents constrained in the nonconvex sets. Numerical simulations verify the results in this paper. • Consensus problem for heterogeneous multi-agent system is studied. • The control inputs of all agents stay in a nonconvex set. • A new distributed H ∞ control algorithm has been developed. [ABSTRACT FROM AUTHOR]

This paper proposes a method to describe the bi-modular behavior of quasi-brittle materials. The approach is based on using multiple loading functions that are associated with the stress state of the material point. The model also includes degradation laws that control the evolution of the internal variables under tension and compression, which allows the representation of the material response with fidelity. The following approach outlines an objective methodology for improving classical models and provides a theoretical framework for developing new constitutive models. This work also presents an updated version of the Mazars damage model, with improved material parametrization through multiple damage laws. Similarly, the modified von Mises model has been extended to include different functions for damage evolution, combining exponential and continuum polynomial laws for tension and compression. A third model was developed to showcase the full potential of the proposed formulation. This model formulates the Lemaitre and Chaboche criterion, typically used for ductile materials, to describe quasi-brittle materials. The model provides a comprehensive characterization of the tension and compression behavior by utilizing various loading functions and multiple damage laws. Numerical simulations of experimental benchmarks are presented to show the performance of the proposal, including a nonlocal approach to avoid strain localization and mesh dependency problems. • A formulation to represent simply the bi-modularity of quasi-brittle materials by isotropic damage models is presented. • The proposal provides versatility to prescribe any damage law, especially with fill constitutive parameters. • The strategy is applied to classical models present in literature providing an enhancement of the model behavior. • The approach can be extended and applied to other models presented in the literature. [ABSTRACT FROM AUTHOR]

• An optimal nutation reduction method based on a flexible contactor is proposed. • A highly efficient data-driven model is established to describe the contact process. • The nutation of a tumbling satellite can be reduced efficiently in the early stage of the de-tumbling tasks. Stabilizing tumbling satellites is a crucial step in ensuring safe on-orbit capture. A new de-tumbling method has been proposed that uses a flexible device, such as a brush or rod, to make contact with the target object and avoid potential collisions. However, this method faces two challenges: (i) The complex rotary motion makes it very difficult to determine the contact position on the target satellite, which is crucial to reduce nutation during de-tumbling. (ii) The conventional finite-element-based dynamic model of the flexible contactor is high-dimensional, leading to unacceptable computing time for on-orbit simulation. To address these problems, this paper proposes an optimal method to efficiently reduce the nutation by predicting the initial contact position for each contact process. Additionally, a fast computation model of the de-tumbling system is established based on a data-driven approach to support real-time prediction. Finally, numerical simulations are conducted to demonstrate the effectiveness and high efficiency of the proposed method. [ABSTRACT FROM AUTHOR]

• A method of uncertainty analysis based on the MP-II model was proposed to examine a case of adhesive assembly. • Uncertainty transfer was constructed by a combination of finite-element simulation and a B-spline surrogate model. • The effect of the uncertainties of three types of bonding defects on the center-of-mass drift was understood. • The reliability index was improved and the parameter intervals of the bonding defects were optimized. Multi-source and strong uncertainties of the adhesive assembly process for high-precision inertial devices are critical issues that result in the current low assembly accuracy and poor assembly consistency. This paper addresses the resulting uncertainty in the center-of-mass drift of the float components of a high-precision inertial device. An interval-based non-probabilistic convex model is used to characterize the uncertainty of the bonding defect parameters of the adhesive assembly process, and the uncertainty transferring from those parameters to the center-of-mass drift is constructed by using a surrogate model and numerical simulations. A reliability analysis is carried out to understand the effect of the uncertainties of three types of bonding defects on the center-of-mass drift, and the sensitivities of the center-of-mass drift to the bonding defects are also found. The results show that the reliability index of the center-of-mass drift obtained under the initial parameter intervals is 0.689, indicating the center-of-mass drift at the risk of being out of the accuracy requirement. By adjusting the parameter intervals of the bonding defects to stabilize the center-of-mass of the assembled components, the reliability index is then improved to greater than 1. [ABSTRACT FROM AUTHOR]

This paper mainly studies the high-order stable numerical solutions of the time-space fractional diffusion equation. The Fourier spectral method is used for discretization in space and the Spectral Deferred Correction (SDC) method is used for numerical solutions in time. Therefore, a high-precision numerical discretization scheme for solving the fractional diffusion equation is obtained, and the convergence and stability of the scheme are proved. Finally, several numerical examples are given to illustrate the effectiveness and feasibility of the numerical scheme. [ABSTRACT FROM AUTHOR]

Fractional calculus has become a potent tool for simulating the complexity of interactions in tumor-immune system dynamics. This paper investigates the existence and uniqueness of its approximation solutions of a fractional model of tumor-immune surveillance. This analysis is essential for proving the validity and dependability of the model and provides a more in-depth understanding of the dynamics of the tumor-immune surveillance system. Second, we examine the fractional model's numerical features. We utilize a numerical technique called the Laplace residual power series method to address the equations' complexity and nonlinearity. By defining the answers as a fractional power series, this method enables us to efficiently approximate the solutions. The use of this technique enables us to investigate the temporal evolution of the tumor-immune system, offering important insights into the stability and behavior of the system. We assess the effectiveness of the Laplace residual power series method in locating approximations through a series of thorough numerical simulations. To ensure the correctness and dependability of our method, we compare the numerical findings whenever possible with well-known analytical solutions. [ABSTRACT FROM AUTHOR]

Rotational moulding is a versatile polymer shaping process used to create enclosed parts from powdered precursors using heat and multi-axis rotation. Controlling the heating process and mould motion is critical to producing high-quality parts, and failures due to incorrect mould coverage or variable wall thickness are common. To date, limited simulation tools exist to predict the motion of the powder within the mould, and operators rely on unreliable prior experience to avoid defects. This paper presents an SPH simulation framework to predict particle flow patterns and powder contact time within a rotating mould. The powder-to-wall contact time was derived from the transient rigid body force (RBF) of different sensors on the mould. The method was compared with the results of DEM simulation and validated by the particle flow pattern of two experimental results. Results showed that the SPH method was capable of simulating particle flow macroscopic properties. The great computing efficiency of SPH compared to DEM simulation was also demonstrated. • Couple the SPH framework with a soil material model to simulate the polymer flow motion during rotational moulding process. • Modelling framework validated by two experimental benchmarks. • Present a significant benefit compared to the DEM method when simulating particle flow with millions of particles. [ABSTRACT FROM AUTHOR]

• The mechanical formula of SSBC shape is derived, revealing the evolution characteristics of SSBC progressive forming. • DIC monitors the evolution characteristics of SSBC, which shows a semi-ellipse deflecting towards the high side. • The roadway stability is controlled by improving stress concentration, and an asymmetric support scheme is proposed. The asymmetric deformation of surrounding rock in inclined coal seam roadway is serious, and its stability is difficult to control. Based on the PU's arch theory and considering the development process of the progressive formation of the self stable balance circle (SSBC), this paper establishes a mechanical model of the SSBC for the right-angle trapezoidal roadway in the inclined coal seam. The mechanical analysis and morphological characterization of the forming process were carried out, and the numerical simulation and physical similarity simulation test were carried out to verify. On this basis, the stability control method of roadway in inclined coal seam is improved, and the asymmetric support scheme of roadway is optimized, which is verified by numerical simulation and field monitoring. The results show that the roadway surrounding rock forms a quasi elliptical SSBC after self stabilization, and the mechanical formula of the shape of the SSBC is derived and characterized. Through numerical simulation and physical similarity simulation experiments, the dynamic evolution process of SSBC is depicted, and the gradual forming evolution characteristics of SSBC are revealed. With the increase of the deformation of the surrounding rock, the effective height and width of the roadway gradually increase, and finally a quasi elliptical SSBC deflecting to the left side of the roadway is formed. Based on this, the asymmetric support principle that can control the stability of surrounding rock by improving the asymmetric stress concentration is proposed, and the asymmetric support scheme is designed, that is, "the anchor bolts (cables) are arranged to the right sidewall, and the sidewall angle weakening area is intensively supported". Through numerical simulation and field monitoring, the support effect is remarkable. [ABSTRACT FROM AUTHOR]

• In this paper a dynamic model of a grid connected synchronous turbo generator with a damper winding is developed using the winding function approach; • Although the continuous end ring damper cage winding is investigated in this paper, one of the advantages of this method is that any damper winding configuration can be modelled, including non-symmetrical and winding where the bars are not equidistant; • The execution of the proposed model on a computer of average performance is incomparably faster than a model based on the finite element method; • On the other hand, the results of these two completely different and independent models show an excellent correlation; • The model presented and described undoubtedly has significant advantages that will only become apparent as it is applied in the future − it allows the optimisation of the damper winding design and a detailed analysis of the influence of this winding on various transient processes. The original dynamic model of the grid-connected synchronous round-rotor generator, also known as synchronous turbo-generator (STG) is presented in the paper. The model is based on the Winding Function (WF) theory and as such it is derived in the natural frame of reference. Depending on the presence or absence of a cage damper winding on the rotor two independent models are derived. The strength and the importance of the derived models lie in the fact that it is possible to consider the real spatial distribution of all the windings in the machine, including the damper winding. The time-dependent currents in all the windings, including the currents in all the bars of the damper cage winding, are the output of the model. In addition, the model execution time on a mid-range computer is a few tens of seconds, which is incomparably faster than the execution time of models based on the Time Stepping Finite Element (TSFE) method, which is measured in days. On the other hand, the results obtained with a completely different and independent TSFE model fully confirm the validity of the results obtained with the proposed WF model. [ABSTRACT FROM AUTHOR]

• The modified phase-field approach and the arbitrary Lagrangian–Eulerian one are able to give physically and quantitatively correct results for modeling electrocoalescence • The exponential relation between volume fraction and electrical conductivity has to be used in the phase-field approach when the conductivity of two phases differs significantly • The power of the volume fraction under the exponent has to be adjusted to centralize the space charge within the interface layer • The phase-field model needs for proper choice of the mobility turning parameter and the interface thickness and has a limited applicability for computing long-term processes • The arbitrary Lagrangian–Eulerian approach is more precise and less resource-intensive than the phase-field one The paper examines two numerical approaches to the simulation of electrical deformation and coalescence processes in water-in-oil emulsions: the phase-field method and the arbitrary Lagrangian–Eulerian approach. The former employs a diffuse interface, while the latter utilizes a sharp interface. The study analyzes the correctness of the computer simulation results and identifies less obvious limits of the applicability of these numerical techniques. The paper is based on a step-by-step comparison of data from two independent numerical models and quantitative verification using original experimental data, including data on unsteady-state droplet deformation and the threshold between coalescence and non-coalescence. The main findings are as follows. Both methods, the modified phase-field approach and the arbitrary Lagrangian–Eulerian one, are fundamentally capable of providing physically and quantitatively correct results for modeling electrohydrodynamic processes in two-phase immiscible liquids. On the one hand, the phase-field method demands thorough tuning and has limited applicability for simulating long-term processes. On the other hand, the arbitrary Lagrangian–Eulerian approach offers greater precision and requires fewer computational resources compared to the phase-field method, although it demands a manual adjustment of geometry when the system's topology changes. It is noteworthy that the phase-field method, without careful tuning, fails to yield quantitatively accurate results; errors, such as discrepancies in the time convergence of droplets under the influence of an electric field, can reach magnitudes of tens of percentages. [Display omitted] [ABSTRACT FROM AUTHOR]

• A comprehensive review on numerical simulations of boiling heat transfer from atomistic to mesoscopic and macroscopic scales is presented. • Critical issues related to nanoscale bubble nucleation mechanisms, pool boiling, and flow boiling are highlighted. • Potential solutions and future research in the field of boiling heat transfer using the MDS, LB and CFD methods are proposed. Boiling is an efficient heat transfer mode with significant potential for thermal management in high-power electronic equipment. However, a comprehensive understanding of the boiling process, which encompasses bubble nucleation, growth, coalescence, slipping, and detachment across various scales, remains challenging. Molecular dynamics simulation, lattice Boltzmann, and computational fluid dynamics methods are popular and powerful tools for investigating boiling heat transfer phenomena at microscopic, mesoscopic, and macroscopic scales. These methods enable researchers to uncover the underlying boiling mechanisms and propose heat transfer enhancement techniques. Therefore, this paper provides a comprehensive review of boiling heat transfer, spanning from atomistic to mesoscopic and macroscopic scales, utilizing these three numerical methods. It addresses critical issues related to nanoscale bubble nucleation mechanisms, pool boiling, and flow boiling, and proposes potential solutions and future researches, supplementing our previous review [Some advances in numerical simulations of multiscale heat transfer problems and particularly for boiling heat transfer, Annu. Rev. Heat Transf., 6 (2022) 217–269]. Besides, by shedding light on the characteristics of these numerical methods in studying boiling heat transfer, this paper aims to foster their development and advance enhanced heat transfer technologies. [ABSTRACT FROM AUTHOR]

• A mechanics–thermotics–chemistry coupling response model for energetic materials was developed based on the MPM3D. • The continuous expansion and thickening of jet due to high-temperature and high-pressure products leads to the decrease of penetration depth and the increase of crater diameter. • The simulation results of reactive materials jet against steel targets agree well with the experimental results. With its unique kinetic penetration/chemical implosion combined damage ability, reactive damage element (RDE) can greatly or even leap the damage power of ammunition warhead, and has a promising application prospect in the field of ammunition. However, due to the high transient and nonlinear characteristics of shock release process, there is still a lack of real-time quantitative research methods to investigate its energy release process under impact loads, which makes it difficult to conduct in-depth analysis of its efficient damage mechanism. In this paper, the Grüneissen equation of state in the P-V-T form is derived to solve the problem of the mechanics–thermotics–chemistry coupling response (MTCCR) of reactive materials (RMS) under impact load, and the calculation model of RMS temperature under impact is established. Based on the pressure equilibrium criterion, a two-phase theoretical model of the reaction flow field between the RMS reactant and the reaction product was proposed. Combined with the impact temperature rise theory, heat conduction theory and the Arrhenius chemical reaction kinetic model, the MTCCR model of RMS was established. The method of material point-impact induced chemical reaction (MPM-SICR) is presented and the energy release behavior of RMS is quantitatively researched in real-time. This method is used to numerically simulate the formation and impact induced energy release behavior of reactive materials jet against steel target. The simulation results are in good agreement with the experimental results, indicating that the model and method proposed in this paper can well characterize the dynamic MTCCR behavior of the RDE under the impact. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive Virtual Reality (VR) based framework for visualizing numerical simulations of geophysical flows in a realistic and immersive manner. The framework allows integrating output data from various mesh-based Eulerian numerical models into a VR environment, enabling users to interact with and explore the terrain and geophysical flows through the VR experience. Three case studies, including a snow avalanche, quick clay landslide, and flash flood in Norway, demonstrate its versatility. The VR environment offers intuitive menus and user interactions, allowing users to read flow depth and velocity values, facilitating a direct link between numerical data and their visual representation. This framework can reshape geophysical flow hazard identification and disaster management by integrating physics-based numerical modeling results into VR Environments, thus enhancing knowledge dissemination among experts, the general public, non-expert stakeholders, and policymakers. The paper also highlights challenges and opportunities identified during the integration, guiding future developments. • A framework that integrates numerical simulations of geophysical flows into VR. • The framework is versatile across different geophysical flow types and numerical models. • Real time visualization of numerical simulation results is still a challenge. • The framework has a potential for disaster preparedness and emergency training. [ABSTRACT FROM AUTHOR]

• A 3D thermal lattice Boltzmann model for simulating melt flow and heat transfer in CZ single crystal growth has been constructed. • The coordinate system transformation is adopted to extend the application of LBM on 3D cylindrical cavities. • The critical Reynolds numbers are increased by introducing a transverse magnetic field. A three-dimensional (3D) thermal lattice Boltzmann model of crystal growth is presented to study the magneto-hydrodynamics (MHD) mixed convection in the melt of Czochralski silicon single crystal growth in this paper. In order to solve the problem of lattice Boltzmann method's difficulty in solving the flow of 3D cylindrical cavity, the 3D physical model of crystal growth is transformed from the Cartesian coordinate system to the Curvilinear coordinate system. And the irregular grids in the Cartesian coordinate system are transformed into regular grids in the Curvilinear coordinate system to facilitate the establishment of the Lattice Boltzmann model. Under the above operations, two coupled distribution functions are established to solve the governing equations. Two D3Q19 models are adopted to solve the melt velocity and temperature. And the 3D lattice Boltzmann modeling of crystal growth with cylinder boundary is realized by interpolation in Curvilinear coordinate system. The comparison with the experiment and other references proves that the proposed model and boundary treatment scheme is correct and it proposes a new way for studying the 3D crystal growth or other similar 3D cylindrical cavity simulations. Furthermore, the unstable melt flow for two cases are also simulated in this paper and the critical Reynolds number are also obtained. Results show that the introduction of the transverse magnetic field enhances the stability of the crystal growth system and increases the adjustable range of crystal rotation parameter. The obtained conclusion has an important reference for adjusting the process parameters during the CZ crystal growth. [ABSTRACT FROM AUTHOR]

The conventional aircraft layout will contain the elevator, aileron, rudder three control surfaces, and thus generate three control moments to adjust the aircraft trajectory and flight attitude. However, the aircraft with multi-control plane flying wing layout needs to choose redundant new control plane configuration, which is quite different from the conventional aircraft layout in both control method and operation mode. Since there are many problems in the aircraft motion mathematical model during the ownership period, which will directly affect the control effect of the flight control system, in order to reduce dynamic error and improve the robustness and accuracy of the flight control system, this paper proposes an adaptive neural network algorithm. Combined with the current operating status of tailless flying wing aircraft and the research status of aircraft control system analysis, this paper mainly discusses the design differences between the adaptive control system and the original control system, based on the empirical case, to clarify the compensation effect of the adaptive control system. [ABSTRACT FROM AUTHOR]

Nowadays, traditional hydrocarbon reserves are depleted. The search for and production of oil and gas in hard-to-reach fields require the development of appropriate computing technologies. Therefore, there is a need to develop novel high-precision computational methods that make it possible to more accurately take into account the features of the geological model, and at the same time save computational resources. In this paper, we have proposed a novel modification of the grid-characteristic method on Chimera grids to take into account the complex geometry of the interfaces of geological rocks. This modification differs from those proposed earlier by using a single background grid with varying elastic parameters of the medium and imposes fewer restrictions on the geological model than the previously proposed options. The computational method proposed in the paper is applicable not only for modeling seismic waves in geological media, but also for modeling ultrasonic and sound study, non-destructive testing of various objects, and in medicine. Also, the proposed numerical method can be applied for a more accurate calculation of seismic waves from earthquake hypocenters and man-made sources. [ABSTRACT FROM AUTHOR]

Today, the exact determination of the parameters of the fracturing of oil and gas fields is of great practical importance. Therefore, an important role is played by computer modeling of the seismic responses from cracks, which correspond to fractured zones actually occurring in nature in terms of the distribution of fracture lengths, positions and rotation angles. Thus, the development of an algorithm aimed at solving this problem plays an important role. In this paper, we have presented the developed algorithm for the placement of cracks in a fractured zone with given geological parameters, such as distribution of lengths, opening, angle of inclination of cracks. The application of this algorithm makes it possible to use in further calculations a geological fractured zone model that is as close as possible to real oil and gas-filled reservoirs. The paper presents the results of test calculations using the grid-characteristic computational method to model wave field scattered on the fractured zone. [ABSTRACT FROM AUTHOR]

The paper presents the concept of the supporting structure and modeling of the main components of the rover, which can transport people and work in autonomous mode. This is ensured by an appropriate design of the rover's support frame and drive wheel system. The paper presents a computer model of selected fundamental drive components affecting the traction capabilities of the vehicle, namely the differential, frame, and wheels. The modeling was performed in a Matlab-SimMechanics environment. In this environment, the model was also assembled into a functional whole, which allows simulating the rover's operation in different terrain conditions. This is presented in the final part of the paper, where the simulation of overcoming an obstacle by the rover presented in this paper is presented. One of the studied cases, an urban obstacle in the form of stairs, was chosen. Displacement diagrams of individual structural elements of the rover prove its high traction and stability capabilities. [ABSTRACT FROM AUTHOR]

Deployable coilable booms have many advantages for use in space, but these kinds of structures sometimes experience a deployment failure mode called 'blossoming'. Blossoming of a coiled boom occurs when the boom stops deploying, and instead unwinds and expands within the deployer. This can occur even in the presence of sprung rollers used to constrain the coil. In the blossoming process, friction between the layers of the coil plays an important role that has only been briefly considered in previous work. In order to be able to model and predict the onset of this phenomenon more precisely, the pressure distribution between adjacent layers of the coil must be known. This paper establishes a numerical model to investigate the pressure distribution within a coiled open-section tape spring boom, then combines this result with theoretical analysis to produce an estimate of the maximum tip force that a deploying boom can withstand before the onset of blossoming. The effect of the roller springs' stiffness and the boom friction coefficient are also taken into account in the simulation. The results of the theoretical analysis and numerical simulation are compared with previous experimental results to provide some practical verification. [ABSTRACT FROM AUTHOR]