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Time-varying linear complementarity problem (TLCP) has received a great deal of attention due to its broad variety of scientific and engineering applications. Several efficient Zhang neural networks are introduced for solving TLCP in this paper. Theoretical analysis shows that the related error function of the model proposed in this paper eventually tends to zero. The state convergence time periods of those Zhang neural networks with three types of activation functions are proved to be finite and can be quantitatively estimated by using some given parameters. Further, it is shown that the proposed neural network is of noise-tolerance, which means the neural network is more appropriate for a wider application. Moreover, in order to implement neural network numerically, a related discrete-time version is also studied. Finally, numerical simulations confirm the analysis of the proposed models concretely. [ABSTRACT FROM AUTHOR]

• A reanalysis theory method based on the inversion of block matrix based on change threshold. • Quickly obtain responses with different accuracy after the structure is modified according to the initial analysis. • The change threshold can control the accuracy and calculation time of the reanalysis results. In the mechanical design industry, it is very time-consuming to convert actual engineering design problems into finite element models, and it is repeatedly modified during the product design process. Each time the structure is modified, computer simulation analysis is repeated, and the product development cycle becomes longer. Therefore, in this paper, a re-analysis theoretical method based on the inversion of the block matrix based on the change threshold is proposed to quickly obtain responses with different accuracy after the structure is modified according to the initial analysis. By modifying the size of the change threshold, the accuracy and calculation time of the reanalysis results are controlled. This reanalysis method shortens a lot of calculation time under the premise of controllable response accuracy. In this paper, numerical calculations are given to show the accuracy of the response under different thresholds, and the efficiency of this method is proved by the finite element model under the same accuracy. [ABSTRACT FROM AUTHOR]

This paper introduces a new methodology for designing and optimizing the performance of hydraulic Cross-Flow turbines for a wide range of operating conditions. The methodology is based on a one-step approach for the system-level design phase and a three-step, successive numerical analysis approach for the detail design phase. Compared to current design methodologies, not only does this approach break down the process into well-defined steps and simplify it, but it also has the advantage that once numerical simulations are conducted for a single turbine, most of the results can be used for an entire class of Cross-Flow turbines. In this paper, after a discussion of the research background, we explain the design process used and the ANSYS®-based CFD model of the turbine in detail. The design process consists of three steps. First, designing nozzle geometry; second, optimizing runner parameters; and third, enhancing turbine performance by analyzing various load conditions. A turbine designed using this process in a simulation case study achieves a peak hydraulic efficiency of 91% and peak overall efficiency of 82% that is maintained for volume flow rates as low as 14% of the nominal value and water head variations up to 30% of the nominal value. • A novel design methodology for hydraulic Cross-Flow turbines is proposed. • The two-dimensional steady state simulations were performed in ANSYS CFX. • Numerical results were validated with experimental data. • The proposed design methodology was used in a case study to design a new turbine. • The designed turbine maintains above 80% efficiency for a range of load conditions. [ABSTRACT FROM AUTHOR]

The sum rate maximization in multiuser MIMO broadcast channels is investigated in this paper. Due to the high computational complexity of non-linear dirty paper coding (DPC), zero-forcing dirty paper coding (ZF-DPC) is proposed as an alternative suboptimal approach. However, traditional ZF-DPC method requires that the number of total receive antennas is less than or equal to the number of transmit antennas. In this paper, we consider the scenario where the sum number of receive antennas may be more than the number of transmit antennas. It is shown that the optimal data stream allocation needs exhaustive search over all possibilities, and the complexity is significantly high. We propose a greedy transmit data allocation scheme that allocates one data stream at each step, the corresponding transmit beamforming vector and receive combining vector are designed to avoid interfering with the previous allocated data streams, and the pre-equalization Tomlinson–Harashima Precoder (THP) technique is adopted to pre-cancel the non-causally known interference caused by the previous allocated data streams. The proposed method is computationally efficient thanks to the low complexity. Simulation results show that this novel method outperforms the methods in the literature. [ABSTRACT FROM AUTHOR]

In the paper the Wiener–Hammerstein (LNL) system is identified with the help of Volterra series and ℓ 1 -constrained least squares. The nonparametric approach to the problem ensures wide applicability of the proposed method, as it does not require an extensive a priori knowledge about the underlying system. In the main part of the paper, the convergence of the identification algorithm is shown for a general class of systems with smooth nonlinearities and stable dynamics, under the assumption that the input is a bounded i.i.d. random signal. The rate of convergence is examined as well. Moreover, the large error of the standard least squares-based models, inherently associated with high dimensional representations (such as those based on Volterra series expansion), is reduced by the imposed ℓ 1 -constraint and hence the method allows for a scarcer data set. In addition, the results of numerical simulations are provided to illustrate the superiority of the proposed method over the standard one. [ABSTRACT FROM AUTHOR]

• Our sketching tasks is unique and has not been used in previous research into immersive 3D sketching despite calls for more innovative methods. • Our observations show that immersive 3D sketching provides unique visualization opportunities while also supporting behaviors that are common in paper-based sketching as well as those found in gesturing, physical modeling and 3D CAD. • This unique combination enables users to engage in visual thinking and visual communication activities in ways that cannot presently be achieved with any other single representation technique. • It is widely accepted that stroke-based immersive 3D sketching is insufficient for the representation of 3D shapes, based on the assumption that precision is more important than flexibility. We show this assumption does not hold for visual thinking and visual communication. • Our findings suggest that the value of stroke-based VR sketching is in its capacity to challenge participants to think more carefully about the representation and visual communication of 3D shapes. Research Highlights Immersive 3D sketching engages users in visual thinking and communication in ways not possible with any other single methodImmersive 3D sketching offers unique visualization opportunities, combining those of traditional physical and digital mediaImmersive 3D sketching challenges users to think carefully about the representation and communication of shapes and spacesImmersive 3D sketching is valued for challenging assumptions that accuracy is more important than flexibility for these tools Paper-based (PB) sketching involves the challenge of representing three-dimensional (3D) shapes on two-dimensional (2D) surfaces. The recent generation of virtual reality (VR) sketching tools offer a way to overcome this challenge. These immersive 3D sketching environments permit the rapid construction of freehand stroke-based 3D models in 3D space while replicating the immediate experience of PB sketching. To explore the potential advantages of VR sketching in visual thinking and visual communication, we conducted investigations with sixteen architectural students engaged in PB and VR sketching tasks. We observed their visualization behavior during VR sketching and their behavior in transitioning between PB and VR sketching. The participants experiences of the two media were also recorded in semi-structured interviews and questionnaires. Our observations show that immersive 3D sketching is a unique form of visual representation that facilitates the rapid and flexible creation of large and detailed (but inaccurate) 3D computer models. It is a multimodal medium that supports visual thinking and communication behaviors associated with PB sketching, CAD modeling, physical model-making and gesturing, all within the same space. This unique combination enables users to engage in visual thinking and visual communication activities in ways that cannot presently be achieved with any other single representation technique. [ABSTRACT FROM AUTHOR]

In order to efficiently perform the direct numerical simulation for shock wave boundary layer interference, a large grid computing scale is needed, and a single graphics processing unit cannot meet the urgent needs of computing. This paper proposes a parallel algorithm based on the architecture of multiple graphics processing units to effectively deal with the direct numerical simulation for shock wave boundary layer interference. The algorithm achieves a high overlap between graphics processing unit computation and boundary data exchange to improve the parallel efficiency when the grid computing scale is large. The working principle of the multi-graphics-processing-unit parallel algorithm is introduced, and the accuracy and feasibility of the algorithm are verified. Finally, through the application of the algorithm in the research of the compression-expansion slope boundary layer, fine flow structures such as large-scale vortex structure, shocklet, and attached shock wave can be captured. As a conclusion, the multi-graphics-processing-unit parallel algorithm proposed in this paper can accurately display the flow field of shock wave boundary layer interference. • A parallel algorithm based on multiple GPUs is proposed. • The accuracy, feasibility, and efficiency of the parallel algorithm are verified. • The DNS of the SWBLI based on the algorithm is tested and analyzed. [ABSTRACT FROM AUTHOR]

This paper discusses some philosophical aspects related to the recent publication of the experimental results of the 2017 black hole experiment, namely the first image of the supermassive black hole at the center of galaxy M87. In this paper I present a philosophical analysis of the 2017 Event Horizon Telescope (EHT) black hole experiment. I first present Hacking's philosophy of experimentation. Hacking gives his taxonomy of elements of laboratory science and distinguishes a list of elements. I show that the EHT experiment conforms to major elements from Hacking's list. I then describe with the help of Galison's Philosophy of the Shadow how the EHT Collaboration created the famous black hole image. Galison outlines three stages for the reconstruction of the black hole image: Socio-Epistemology, Mechanical Objectivity, after which there is an additional Socio-Epistemology stage. I subsequently present my own interpretation of the reconstruction of the black hole image and I discuss model fitting to data. I suggest that the main method used by the EHT Collaboration to assure trust in the results of the EHT experiment is what philosophers call the Argument from Coincidence. I show that using this method for the above purpose is problematic. I present two versions of the Argument from Coincidence: Hacking's Coincidence and Cartwright's Reproducibility by which I analyse the EHT experiment. The same estimation of the mass of the black hole is reproduced in four different procedures. The EHT Collaboration concludes: the value we have converged upon is robust. I analyse the mass measurements of the black hole with the help of Cartwright's notion of robustness. I show that the EHT Collaboration construe Coincidence/Reproducibility as Technological Agnosticism and I contrast this interpretation with van Fraassen's scientific agnosticism. • First image of a black hole obtained by the Event Horizon Telescope. • A new type of experiment and Cartwright's interpretation of reproducibility. • The paper discusses Galison's philosophy, machine learning and computer simulation. • Hacking's elements of laboratory science and the argument from coincidence. • The EHT experiment and van Fraassen's empiricism. [ABSTRACT FROM AUTHOR]

This paper established the temperature differential model of temperature-controlled materials, performed the numerical simulation of the relationship between mechanical properties and temperature of temperature-controlled materials, and discussed the stress-strain relationship of temperature-controlled materials at different temperatures. The final stimulation experiment showed that temperature-controlled materials have the advantages of large energy storage density, approximately constant temperature and compact structure during phase change. The results of this paper provide a certain reference for the further researches on the numerical simulation of forced bending deformation of temperature-controlled materials based on the differential equation model. [ABSTRACT FROM AUTHOR]

Numerical simulations are used in this work to investigate aspects of microstructure and microsegregation during rapid solidification of a Ni-based superalloy in a laser powder bed fusion additive manufacturing process. Thermal modeling by finite element analysis simulates the laser melt pool, with surface temperatures in agreement with in situ thermographic measurements on Inconel 625. Geometric and thermal features of the simulated melt pools are extracted and used in subsequent mesoscale simulations. Solidification in the melt pool is simulated on two length scales. For the multicomponent alloy Inconel 625, microsegregation between dendrite arms is calculated using the Scheil-Gulliver solidification model and DICTRA software. Phase-field simulations, using Ni–Nb as a binary analogue to Inconel 625, produced microstructures with primary cellular/dendritic arm spacings in agreement with measured spacings in experimentally observed microstructures and a lesser extent of microsegregation than predicted by DICTRA simulations. The composition profiles are used to compare thermodynamic driving forces for nucleation against experimentally observed precipitates identified by electron and X-ray diffraction analyses. Our analysis lists the precipitates that may form from FCC phase of enriched interdendritic compositions and compares these against experimentally observed phases from 1 h heat treatments at two temperatures: stress relief at 1143 K (870 °C) or homogenization at 1423 K (1150 °C). [ABSTRACT FROM AUTHOR]

• The effects of discontinuity in the elasticity and damping on the dynamics of a non-smooth electromechanical system are investigated in this paper. • Numerical simulations and experimental results of non-smooth electromechanical system reveal the phenomenon of discontinuity, bifurcation and chaos. The effects of discontinuity in the elasticity and damping on the dynamics of a non-smooth electromechanical system are numerically and experimentally studied in this paper. The amplitude curves are obtained, bifurcation diagrams, phase portraits, and time traces showing the transition from periodic to chaotic motion. A prototype device is designed and built. The experimental results of this device are consistent with results from theoretical investigation and convincingly show the phenomenon of discontinuity, bifurcation and chaos. The non-smooth electromechanical system proposed and studied in this paper can be used for drilling, cutting and vibration absorber. [ABSTRACT FROM AUTHOR]

In this paper, fully coupled particle resolved direct numerical simulations are used for heat transfer calculations. For modelling fluid velocity and temperature, the immersed boundary method (IBM) is used. Particle-particle heat transfer is modelled using well-established relations from the literature. Two-way coupling between particles and fluid is obtained using a body force that is a function of the solid volume fraction present in the fluid grid cell. Results are compared with those of spouted bed experiments to validate the simulations, and good agreement is observed. At the end of the paper, several interesting characteristics of spouted bed are obtained using simulations. The speedup of the method used for simulations was tested on multi-core CPU clusters. It is observed that the simulations scales almost linearly with the number of CPUs (tests were done up to 500 CPUs), showing the capability of the particle resolved DNS to be used on multi-CPU architectures. Distribution of particle temperatures by (a) Simulations (b) Experiments at packed bed conditions; Distribution of particle temperatures by (c) Simulations (d) Experiments at spouting condition. [Display omitted] • Heat transfer in spouted bed is modelled using particle resolved DNS. • Simulations results agree well with experiments. • The underlying physics of heat transfer in a spouted bed is studied by simulations. [ABSTRACT FROM AUTHOR]

This paper studies the stabilization analysis problem of a class of incommensurate fractional-order memristor-based neural networks with multiple time-varying delays (IFOMNNs-MTDs). In previously published studies of IFOMNNs-MTDs, the controller is usually designed as a general delay-independent feedback controller. Due to the simple form of the feedback controller, less system information is used and less adjustable parameters are considered, which limits the flexibility and control effect of controller. Specially, the use of delay information is insufficient in the existing results, which will make the controller insensitive to the influence of delay factors and affect the control performance. Thereby, the accurate analysis of the dynamic characteristics of IFOMNNs-MTDs by designing appropriate controller needs further study. This paper aims to propose a new delay-dependent controller to improve the stabilization analysis of IFOMNNs-MTDs. Firstly, a delay-dependent distributed controller with distributed control gain and time-delay state summation term is proposed, which accords with the transmission law of activation function weights and is helpful to consider the historical information (i.e., time delay factors) of system. Thereby, the flexibility and control effect of controller are improved by adding control parameters and improving the use of system information. Secondly, a new less-conservatism stabilization criterion of IFOMNNs-MTDs is established by using the designed controller. Moreover, the controller gain can be searched in a large range by using the established criterion. Finally, a numerical simulation is provided to verify the validity of the obtained results. [ABSTRACT FROM AUTHOR]

This paper investigates the distributed optimal coordination (DOC) problem for multiple heterogeneous linear systems over strongly connected communication networks. By exploiting output regulation techniques, constructing a Laplacian matrix based on the outdegree, and assigning each agent an additional scalar state variable, a new DOC algorithms is developed, which can solve the DOC problem using the outdegree information of all agents. In contrast to the existing results, this paper presents a new technique to solve the DOC problem for multiple heterogeneous linear systems over weighted-unbalanced communication networks. Finally, numerical simulations are presented to illustrate the effectiveness of the designed algorithm. [ABSTRACT FROM AUTHOR]

In this paper, we consider the distributed state estimation problem of continuous-time linear time-invariant (LTI) systems, where communication channels are attacked by stochastic impulsive sequences. In a networked system, the communication channel between an agent and its neighbor is vulnerable to being attacked. Continuous attacks have been widely studied so far, but with the development of attack techniques, intermittent attacks have been emerging, which are more difficult to be identified and detected, and have not been well portrayed and studied. Therefore, this paper investigates a random intermittent injection attack, which leads to abrupt and random changes of the state information transmitted by the neighbors. First, this attack is modeled as a stochastic impulsive sequential attack, where both its impulsive time and impulsive intensity are random. Then a distributed observer under stochastic impulsive sequential attack is proposed. Since the impulsive attack destroys the stability of the system, in order to attenuate the impact of the impulsive attack, a large feedback gain is necessary. By using the graph theory, matrix theory and stochastic analysis, sufficient conditions for the existence of the distributed observer in the sense of mean square and in the sense of almost sure are presented, respectively. Finally, the effectiveness of the proposed distributed observer is verified by numerical simulations. [ABSTRACT FROM AUTHOR]

• The dynamic characteristics of heat pipe cooled reactor during the early startup period are discussed. • Power pulse phenomenon which can cause the obvious increase in fuel temperature should be deserved special attention. • Only until all heat pipes startup successful, can heat generated in reactor be efficiently transferred to the energy conversion system. Heat pipe cooled reactor has unique characteristics during reactor startup and power operation due to the design of solid reactor and heat pipes heat transportation. In this paper, numerical simulation of the early startup period of typical heat pipe cooled reactor is carried out. Based on the calculation, it can be found that it takes about 6000s to complete startup from the room temperature, and fuel temperature reaches about 730 K. Important phenomenon of power pulse is also discovered. For power pulse, reactor power can rapidly increase from 80 wt to 40kWt with about 220 s, leading to rapid increase in fuel temperature from 300 K to 420 K. It is also found that heat pipes may cool down again if reactor power is low enough. Studies carried out in this paper show the dynamic characteristics and point out the key issues that need to be focused on during the reactor early startup period. [ABSTRACT FROM AUTHOR]

This paper focuses on platoon control of autonomous vehicles (AVs) equipped with V2X technology and the phenomenon that the large platoons are split into multiple sub-platoons due to the communication restrictions. At the same time, with the popularity of AVs and connected human-driven vehicles (CVs), this paper also carries out the research of mixed traffic flow mixed with AV platoons, CVs and regular human-driving vehicles (RVs). According to the characteristics of the different types of vehicles, this paper extends the corresponding car-following models based on intelligent driver model (IDM), and considers the functional degradation of AVs under different car-following modes. In this paper, the AVs are classified into the second-level degenerated AV (D2AV), the first-level degenerated AV (D1AV) and the normal functioning AV (NAV) based on the differences in car-following modes. The degradation of AVs is represented via the change of communication topologies and models. Linear stability analysis is conducted. Numerical simulation shows that the higher level of AV degradation, the worse the stability of traffic flow. Under the same conditions, the more sub-platoons and the larger maximum size of sub-platoons, the better the stability of the traffic flow. The increase in communication strength of AVs is also beneficial to stability of traffic flow. In order to compensate for degradation, an adaptive gain feedback control strategy is proposed. Simulation shows that the adaptive gain feedback strategy can effectively improve the ability of the traffic flow to resist disturbances, reduce the fluctuations of velocity and acceleration, and contribute to the stability of platoon system and traffic flow. • A general car-following models are established, including eight types of vehicles. • Considering graded degradation, linear stability analysis is conducted. • Exploring the effect of the various factors of sub-platoon on traffic stability. • Proposing an adaptive gain feedback control strategy and proving its effectiveness. [ABSTRACT FROM AUTHOR]

• We provide a universal tensor CUR framework for the tensor completion problem that incorporates the Tucker CUR and tubal CUR (t-CUR) approximations. Additionally, we extensively compare the performance of the proposed tensor CUR models for reconstructing image/video datasets with missing pixels. • We propose smooth tensor CUR completion algorithms to recover incomplete data tensors with structural missing patterns or high missing rates. In our experiments, the effectiveness of various smoothing methods is also contrasted. • We provide extensive simulations on various data tensors such as images and videos. The simulation results indicate that the proposed algorithms are very fast and outperform most of the state-of-the-art completion algorithms. This paper presents a framework that suggests the utilization of cross tensor approximation or tensor CUR approximation to reconstruct incomplete images and videos. The proposed algorithms are significant due to their simple implementation and low computational complexity. We further suggest the use of efficient smooth tensor CUR algorithms for data tensors with structural missing components or high missing rates. These algorithms make the sampled fibers smoother and subsequently apply the proposed CUR algorithms. Our numerical experiments exhibit that this smoothing process provides significant benefits. The primary contribution of this paper is to design and examine enhanced multistage CUR algorithms with smoothing pre-processing for the tensor completion problem. The secondary contribution includes a thorough analysis of the efficiency of image reconstruction using four distinct CUR strategies via comprehensive computer simulations. Our simulations showed clearly that the suggested algorithms perform comparably to, and frequently even better than, the majority of the current state-of-the-art methods developed for the tensor completion problem while at the same time they are much faster. Additionally, we offer the MATLAB codes on GitHub for use in a variety of applications. To the best of our knowledge, no research or comparisons of CUR (cross approximation) algorithms for image and video completion have been done to date. [ABSTRACT FROM AUTHOR]

The nuclear reactor core melting accident can cause the leakage of radioactive materials, resulting serious harm to the surrounding environment and the safety of the public. For modern PWR, if the core structure was melted in a severe accident, the generated melt will move downward and interact with the remaining coolant at the lower head, resulting a series of physical phenomena. In this paper, the numerical model based on the VOF to DPM method is presented to analyze physical processes of the interaction between melt jet and coolant. The influence of coolant phase change on the jet breakup length, degree of fragmentation, and particle diameter of melt debris are analyzed under different conditions. This paper analyzes the impact of the incident velocity of melt, the incident diameter, the density ratio of melt and coolant on the jet breakup length based on Saito's empirical formula, and compares the simulation results with the empirical formula. The working condition of Yutaka experiment is simulated in this paper and the diameter distribution of the broken fragments is analyzed, as well as the influence of the incident temperature, incident mass and incident velocity of the melt on the average mass diameter of the generated particles. The numerical results reach a good agreement with the experimental data. This work provides a feasible numerical scheme for the analysis of melt jet entering the lower head coolant under accident conditions. [ABSTRACT FROM AUTHOR]

• The mathematical model on the grounding resistance of the vertical electrode is proposed. • Accuracy of the mathematical model is proved by computer simulation analysis and the field measurement examination in this paper. • The mathematical model can be used in the design of vertical grounding electrode effectively. In this paper, a mathematical model on the grounding resistance of vertical electrode is proposed. The proposed mathematical model is modeled with consideration of the effects of parameters such as the length and diameter of vertical electrode, the soil resistivity and the embedding depth. This mathematical model can be applied effectively to the design of grounding system using vertical electrode in harmonious soil with the resistivity values less than 900Ω∙m. The accuracy of proposed model is proved by the simulation analysis and measurement examination of the electric field in this paper. [ABSTRACT FROM AUTHOR]

• The thermal stress in ADP crystals grown by SCM was studied. • The distribution of thermal stress under the different conditions was presented. • The effect of heat transfer on thermal stress was analyzed. • The cracking was studied combined with the supersaturation distribution. Transient numerical simulations were carried out to describe the temperature and thermal stress in ADP crystals during the steady rotation by solution circulating method (SCM). In a related paper (J. Crystal Growth 574 (2021) 126343), the effects of flow and heat transfer on the distribution of the supersaturation on the crystal face was discussed. This paper presents the corresponding results concerning the heat transfer occurring in the crystal. Emphasis is placed on studying the temperature and thermal stress distribution, since it is critically involved in the processes of crystal cracking. The evolution of the temperature and thermal stress in the crystal are studied as a function of crystal rotation rate, inlet velocity, and inlet temperature and crystal size. The numerical results seem to indicate that, as the rotation rate increases, the value of the σ max in crystal decreases and then increases, while the values of the σ max on crystal surface is increased. The increases of the inlet velocity and the inlet temperature lead to the increase of the σ max. Finally, As the crystal size gets large, the possibility of cracking arising in pyramidal zone is increased obviously. [ABSTRACT FROM AUTHOR]

• Unlike [7,8] and [31] , which designs the controller under the assumption that the system states are available and the Lipschitz condition is needed for the nonlinear term. This paper designs the NNs-based observer to estimate unknown states and approximate nonlinear terms simultaneously, which guarantees the robustness and stability of the MASs can be improved. • Compared to Yang et al. [20] , He et al. [21] , Ma et al. [22] , Liu et al. [23] , Fu et al. [24] , Zhao and Yang [25] dealing with deception attacks by using the global topology information, the fully distributed intrusion-tolerance control scheme is designed in this paper to achieve the consensus control for multi-agent systems that suffer from deception attacks, which only uses adjacent agent information in the design process of controller. In addition, the impact of the error signal injected by the attacker on the adaptive parameters are considered. This paper proposes a novel resilient intrusion-tolerance control scheme to solve the consensus control problem of multi-agent systems (MASs) under deception attacks. Consider the state unavailability of MASs with unknown nonlinear terms, the unmeasurable state is estimated by designing the neural-networks(NNs)-based observer. Then, a fully distributed intrusion-tolerant adaptive protocol is developed to implement the consensus control task. The designed control strategy only involves the agent states that interact with the neighboring agent and does not relate to the whole communication topology information. The designed controller can ensure that the consensus error of the nonlinear MASs is eventually ultimately bounded under deception attacks. Finally, a numerical simulation is provided to verify the feasibility of the designed scheme. [ABSTRACT FROM AUTHOR]

• A novel tether-net release mechanism was proposed to improve the capture of space debris. • Vibration tests were conducted to verify the materials' toughness and mechanisms. • The net release mechanism of the fabricated model was experimentally verified. • The best combination of net size and spring constant was selected. This paper presents the general concept, mechanism, and components of a novel net-launching device for capturing space objects. The novelty of the solution and its distinct features, which ensure safer and more sustainable in-space performance as compared with the known previous solutions, are also described. Furthermore, issues related to the design parameters of the device and its parts are highlighted, and detailed calculations and analyses are presented. Examples of design solutions for real-scale applications involving the removal of space debris and a miniaturized mechanism (as a case study) are presented. The features of the proposed device are highlighted, and its efficacy and potential are demonstrated using numerical simulations and field experiments. [ABSTRACT FROM AUTHOR]

In this paper, an efficient dimension splitting method is applied to the two-dimensional (2D) and three-dimensional (3D) Cahn-Hilliard type equations with significant applications in physical, biological and computer science. The proposed method can greatly reduce the storage requirements and computational complexity in two and three dimensions, and preserve the high precision and mass conservation. The dimension splitting method is based on auxiliary variables for spatial derivative terms and the operator splitting approach. It converts the 2D or 3D problem into a series of one-dimensional (1D) problems which can be solved by using multi-thread. The stability and accuracy of the proposed method are improved by a local stabilizing approach and extrapolation. The analyses of discrete energy and discrete mass conservation property are shown. Numerical examples confirm the advantages of proposed method. And a variety of simulations, such as the phase separations, curvature driven flows, diblock copolymers, tumor growth and volume restoration, are performed with respect to practical applications. • Dimension splitting method for Cahn-Hilliard type equations. • The global stability is achieved by the local stability of solving each sub-problem. • Fourth-order mass conservative scheme based on the compact differencing and extrapolation. • A large number of numerical examples for practical applications. [ABSTRACT FROM AUTHOR]

Industrial processes are subject to various noise disturbances that lead to the stochastic nature of the modeled system and the uncertainty of the model parameters. In this paper, a variational Bayesian State Space Model (VBSSM) model is developed for dynamic process monitoring, allowing the uncertainty of parameters to be described by probabilities. The conjugate prior allows the posterior distribution of the parameters to be estimated iteratively through the Rauch Tung Striebel (RTS) smoothing estimation with the VB framework. The next state can be better predicted even in the presence of noisy perturbations, and imperceptible correlations among multiple variables can be found. By maximizing the lower bound of the objective function to approximate the true posterior distribution of the parameters, the fault detection index is constructed by the corresponding residual. Finally, the effectiveness and superiority of the proposed method is verified by numerical simulations, Tennessee Eastman process and hot rolling industry examples. • This work develops variational Bayesian state space model (VBSSM) based on variational Bayes, where the dynamic properties of the data are described directly through the SSM. • The increased dimensionality of the state space due to the Cholesky decomposition is avoided. • The developed VBSSM method describes the parameter uncertainty probabilistically instead of point estimation and therefore avoids overfitting. [ABSTRACT FROM AUTHOR]

This paper investigates the Z-type control method to stabilize species populations and make them converge to desired values in a two-species predator–prey model with time delay in the prey species' growth rate. Direct controllers that assume both species' growth rates can be altered through human intervention and indirect controllers that assume only one species' growth can be changed at will are constructed. The Z-type method of construction is theoretically justified, and the potential for certain non-linear activation functions to speed up the control process is highlighted. A general procedure for discretizing state-space systems using the Euler forward formula is described. The discrete versions of the directly and indirectly controlled systems are provided. All Z-type controllers constructed are validated through numerical simulations. • A time-delay predator–prey system turns stable and convergent under Z-type control. • Certain non-linear activation functions accelerate error convergence in the process. • Numerical simulation is conducted to validate the Z-type controllers. • Z-type controllers discretized via Euler's formula can be implemented digitally. [ABSTRACT FROM AUTHOR]

In this paper, we study the global stability of delayed genetic regulatory networks (DGRNs) with Hill-type activation (or inhibition) functions based on the mixing monotone semiflows approach, where Hill coefficients can be arbitrary positive real number. A new result on the global stability of DGRN is given in the case that all Hill coefficients are less than or equal to 1. In addition, for all Hill coefficients greater than 1, a new sufficient condition for global convergence of DGRN is given, which is less conservative than the condition of the existing correlation results. Finally, two numerical examples and simulations are given to explain the effect of obtained results. [ABSTRACT FROM AUTHOR]

This paper presents an approach to ensuring the safety of a landing module on a threat during its splashdown in the World Ocean. We propose mathematical methods and software to predict the main hydrophysical disturbances from underwater vehicles, which are necessary to estimate artificial anomalies on the sea surface. • Detection of underwater objects ensures safety of the spacecraft splashdown. • Underwater object creates identifiable hydrophysical anomalies. • Computer technologies can predict hydrophysical anomalies. • Analysis of radar images of anomalies allows to detect an underwater object. [ABSTRACT FROM AUTHOR]

Various celestial bodies contain cracks. Also, cracks can be in the skin of aircraft, while their growth is one of the main mechanisms for the breakup of structures. This paper presents a study of one and two rectangular cracks. The influence coefficient (the ratio of the stress intensity factors for the fracture system to the corresponding value for a single crack of the same size) was chosen as the quantity under investigation. The final shape of the crack in the case of its growth is also studied. The following methods were used to model this process: the three-dimensional boundary elements method of discontinuous displacements, in which stress and displacement field is a finite series of expansions of analytically found functions, as well as the two-dimensional boundary elements method of discontinuous displacements, which takes into account the twisting of a growing crack along the stress field at the tip. • Single rectangular crack and system of two parallel cracks were investigated. • For rectangular crack growth is likely to happen from the centers of the sides. • The danger of two parallel cracks depends significantly on their relative position. • Pair of uniaxial cracks is less dangerous then a single crack of the same size. • Non-overlapping cracks in close planes are the most dangerous. [ABSTRACT FROM AUTHOR]

• The coupled characteristics of compressor and expander are investigated. • Model of the whole air refrigerator is established by the coupled characteristics. • Effects of turboexpander inlet temperature and first stage compression ratio. • Characteristics of the air refrigerator under variable cooling capacity. Reverse Brayton air refrigerators are environmentally friendly and have broad application prospects, which can work under various conditions. In this paper, the characteristics of a open-loop air cycle for room temperature applications were investigated. The compressor and turboexpander in the cycle were modeled by numerical simulation. Based on coupled characteristics of the compressor and expander, a system model was established. The effects of the first stage compression ratio and the expander inlet temperature on the refrigerator performance were studied by experiments. The accuracy of the system model is verified by comparing with the experiments, and the maximum deviations of expander rotating speed and supplied mass flow are 3.1% and 4.83%, respectively. With the increase of the first-stage compression ratio and the decrease of expander inlet temperature, the mass flow rate of supplied air and cooling capacity of the cycle increase. The expander efficiency can be maintained near the optimal value. At the expander inlet temperature of 313.2 K, COP drops by 31.7 % when the cooling capacity is reduced from 3.34 kW to 0.74 kW. [ABSTRACT FROM AUTHOR]

Hydrogen energy can be produced by the decomposition of hydrogen and carbon compounds. A numerical analysis method of accuracy and efficiency provides important reference value for optimizing development plans and predicting production performance of hydrogen and carbon compounds. In this work, embedded discrete fracture model (EDFM) is used to study the production performance of hydrogen and carbon compounds under non-liner seepage under the threshold pressure gradient and complex fracture systems consist of the hydraulic fractures, secondary fractures, natural fractures. A dual-permeability model of the same case is also constructed as a comparison study to analyze the development of hydrogen and carbon compounds. On this basis, the influence of threshold pressure gradient on production of hydrogen and carbon compounds is quantitatively evaluated in this paper to modify the numerical model and a novel method for the simulation of fractured hydrogen and carbon compounds reservoirs is provided. Through model comparison, the impact of fractures in the reservoir on production can reach 289.1%. A dual-permeability model of the same case is also constructed as a comparison study to analyze the development of the reservoir and the result shows a 7.9% distinction on the cumulative production. It is analyzed that when the threshold pressure gradient is increased from 0.1 MPa/m to 0.6 MPa/m, the output decline of different models ranges from 6% to 15% and a novel method improving model fidelity for the simulation of fracture reservoirs is provided. • A new numerical simulator was presented to study production performance in shale reservoirs. • Both embedded discrete fractures and the threshold pressure gradient were considered into model. • The method provides a new idea and reference for future horizontal well fracturing model. [ABSTRACT FROM AUTHOR]

The flow of temperature distribution through a medium in thermodynamic studies plays an important role in understanding physical phenomena in chemical science and petroleum engineering, while temperature distribution indicates the degree of reaction that must be undergone to obtain the final product. Therefore, this paper aims to present and apply the exponential matrix algorithm (EMA), differential transformation algorithm (DTA), and Runge-Kutta (RK5) to simulate the temperature distribution in five heating tanks in series. successive preheating of multicomponent oil solutions. A mathematical model of the energy balance equations of the reservoir is considered. Two computer experiments were performed to test and investigate the relationship between two constant parameters appearing in the model. Numerical simulation of saturated steam T steam temperature of 500 °C and 1000 °C used to heat the tanks and initial temperature T 0 35 ° C a n d 100 ° C of the first tank feed oil are considered. The fluids in the reservoirs were considered homogeneous throughout the experiment and changes in the cell configuration at two constant parameters were presented in the 2D plot control with the use of the MAPLE 18 software package. The study revealed the nature of the temperature distribution that the higher temperature distribution is obtained when heat is transferred from the first tank to the fifth tank and the reverse reaction occurs in all five reservoirs when ψ = 0.0025 and ω = 0.0025 respectively. Numerical results obtained are prototypes of oil temperature distribution performed under laboratory conditions in a thermodynamic experiment. [ABSTRACT FROM AUTHOR]

• We consider competition between sensitive and resistant subpopulations as an optimal control problem. • Bespoke objective functional directly penalizing domination of resistant subpopulation is analyzed. • Properties of singular arc appearing in this optimal control problem are studied. • Penalizing chemoresistance gives rise to singular arcs in the optimal control. • Numerical simulations show that non-trivial competition has a major impact on the structure of optimal control. Emergence of pesticide-resistant strains of pests, antibiotic-resistant bacteria or chemotherapy-resistant tumor cells is a major obstacle standing in the way of effective external control of undesirable growth of these populations. Once the resistant subpopulation becomes dominant the means to control the population are effectively lost. Prevention of resistance may be therefore considered one of the optimal control goals to ensure long-term controllability. In this paper we formulate nonlinear optimal control problem motivated by the question of controlling the growth of two coexisting subpopulations representing two phenotypes of the same species. However, the model we consider is a standard competition model with populations following logistic growth, and therefore it is more general and can be used also when two competing populations are taken into account. We consider a situation when the control (e.g. pesticide or drug) has effect only on the specimen belonging to one (sensitive) population while having no effect on the other (resistant) population. We use a non-standard, nonlinear objective functional in which, aside from penalizing the overall size of both populations, we include an additional, nonlinear term to ensure that the control-sensitive population remains the dominant one. It is shown how the resistance penalty gives rise to locally-optimal singular controls which are key to achieving the balance between resistant and sensitive populations whenever the subpopulations are similar in terms of the model parameters. Analytic properties of the singular arcs and the structure of optimal control are investigated. Both theoretical and numerical results strongly suggest that the optimal control contains a singular interval. [ABSTRACT FROM AUTHOR]

Understanding the formation of impact craters on planetary surfaces has fundamental importance in geology, impact dynamics, and planetary sciences. The finite element-smoothed particle hydrodynamics (FE-SPH) adaptive method combines the advantages of smoothed particle hydrodynamics (SPH) and finite element method (FEM) in solving hypervelocity impact (HVI) problems. Employing FE-SPH adaptive method is a new idea for the analysis of planetary impact cratering which is different from impact-simplified arbitrary Lagrangian Eulerian (iSALE). In this paper, we establish a complete numerical model of planetary impact cratering through the FE-SPH method, including material failure criterion, thermodynamic analysis, gravity preloading, etc. We reproduce the numerical results by Collins et al. (2012) and highly consistent results are obtained through comparative analysis. This study simulates the formation process of simple and complex impact craters, and the temperature, pressure, density, and geometric shape of the impact zone can be quantitatively obtained. We further analyze the distribution of polymorphs and rock fragmentations in the impact zone based on the theories of shock metamorphism. The proposed analysis method may assist geologists in conducting geological studies. • We establish a complete numerical model of planetary impact cratering different from iSALE. • We analyze the distribution of high-pressure polymorphs based on shock metamorphism. • The FE-SPH model has higher numerical precision for planetary cratering impacts. [ABSTRACT FROM AUTHOR]

This paper presents a systematic methodology, called the MBP-preserving iteration technique, to develop the maximum bound principle (MBP) preserving numerical algorithms for a class of semilinear parabolic equations. Two types of MBP-preserving iterations are suggested to solve two well-known θ -weighted schemes, respectively. Within some mild time-step constraints, the corresponding iteration solutions are proved to preserve the MBP property at each iteration step so that the numerical scheme has a uniquely MBP-preserving solution. In addition, concise error estimates in the maximum norm are established on nonuniform time meshes. Several numerical examples coupled with an adaptive time-stepping strategy are implemented for the Allen-Cahn model to confirm the theoretical findings and demonstrate their effectiveness for long-time numerical simulations. [ABSTRACT FROM AUTHOR]

In this paper, we study the asymptotic stability of a particular class of linear 2D discrete Fornasini-Marchesini models. The solutions of the model can be expressed in terms of doubly indexed sequences in a simple way only when the matrices describing the model commute. In this situation, we are able to analyse directly the limit of all the trajectories. By doing so, we propose the first necessary and sufficient condition for asymptotic stability of Fornasini-Marchesini matrix models. This condition is not computationally challenging as it is ultimately based on the eigenvalues of the matrices describing the model. We support our result with numerical simulations. [ABSTRACT FROM AUTHOR]

Currently, the numerical simulation of final 3D parts obtained by additive manufacturing (AM) using the selective laser melting (SLM) and the electron beam melting (EBM) techniques is still a challenging task. Meanwhile, ANSYS Parametric Design Language (APDL) efficiently offers an alternative way to model the process of AM, especially modeling the thermo-mechanical problem. One of the vital parameters of the AM process is the laser scanning pattern. It influences the temperature history and the residual stress distribution of the structure, which extensively influences its final shape and strength. Since the conventional laser scanning patterns cannot accurately fit the contour boundary of structure, and it also leads to the accumulation of deformation by the use of the same path for the each layer, in this paper, we propose several advanced joint path strategies, which can uniformly distribute the deformation through a series of the basic path patterns with the continuously rotating increment, to analyze the thermo-mechanical response of Ti-6Al-4V Taylor bar, and consequently the numerical simulation is solved to reveal that the centrosymmetric joint path strategy is the optimal strategy. • Advanced joint path strategies based on irregular hexahedrons are proposed. • Advanced joint path strategies on the mechanical response are studied. • A suitable joint path strategy is generated to form part having the closest shape to the desired CAD. [ABSTRACT FROM AUTHOR]

This paper mainly studies the periodicity and exponential stability for a class of inertial neural networks (INNs) with time-varying delays. Without utilizing standard reduced-order transformation, by using the continuation theorem and Cauchy–Schwarz inequality, delay-dependent criteria shown by some algebraic inequalities are derived to ensure the existence of periodic solutions. Furthermore, by means of the fundamental inequality and constructing a modified delay-dependent Lyapunov functional, global exponential stability analysis is obtained based on the derived delay-dependent criteria. In comparison with the reduced order approach applied to the INNs and delay-independent criteria provided for the INNs in the existed literatures, the results obtained in this paper are new. Finally, numerical simulations are carried out to verify the main results. [ABSTRACT FROM AUTHOR]

This paper proposes a theoretical solution for multi-span continuous sliding cable structures, which were usually analyzed by numerical simulations. Firstly, the analytical equation for the unstressed length of single-span cable based on the undeformed configuration is derived, in which the tension forces at the ends can be accurately calculated. Then, according to the tension balance condition at sliding joints and the assumption of invariant total unstressed cable length (ITUL method), multivariate transcendental equations for the sliding analysis of multi-span cable structures with and without considering friction are established and solved by multiple Newton-Raphson iterations. Moreover, a theoretical method based on the assumption of invariant total cable length (ITL method) is also proposed and the applicability of the ITL method is investigated. Finally, four typical examples are analyzed by the ITUL method, and the accuracy of the ITL method as well as some existing numerical simulations is evaluated. The result shows that the ITUL method proposed in this paper is more accurate and reliable than the ITL method. The ITUL method can provide a theoretical basis for the design and analysis of multi-span sliding cable structures. [ABSTRACT FROM AUTHOR]

This paper investigates the problem of global μ -synchronization of impulsive pantograph neural networks. In this paper, new concept of ν -asymptotic periodic impulsive interval T a s y ν is proposed for pantograph networks. By employing the Lyapunov method combined with the mathematical analysis approach for impulsive systems, some useful criteria are derived to guarantee the global μ -synchronization of coupled pantograph neural networks when the asymptotic logarithmic periodic impulsive interval T a s y ln < ∞ and T a s y ln = ∞ , respectively. Especially when T a s y ln = ∞ , as long as the networks are unstable, impulsive control cannot achieve synchronization regardless of the size of the impulse gain. Numerical simulations are exploited to illustrate our theoretical results. [ABSTRACT FROM AUTHOR]

This paper investigates the fault-tolerant tracking control issue for a class of discrete-time systems with sensor fault. A novel model-free adaptive fault-tolerant tracking control scheme is proposed by utilizing the dynamic linearization approach, in which only input/output (I/O) data of controlled plant are required. Moreover, due to the characteristics of simple structure and powerful approximation ability, RBF neural network (RBFNN) is introduced to approximate the fault dynamics after the sensor fault is detected. The approximated fault dynamic is utilized to reconstruct the controller. The major feature of this paper is that the whole fault-tolerant tracking controller structure is derived from the dynamic linearization of the ideal controller, rather than the criterion function. Finally, the proposed model-free adaptive fault-tolerant tracking controller is verified to be effective by numerical simulations. [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]