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Several real-life problems that involve a time delay are modeled using fractional time-delay systems. However, most studies related to these systems assume that the delay is already known, which is not the case in practical scenarios where the delay is often uncertain or unknown. To address this issue, this paper proposes an algebraic and robust method to estimate the input delay for a class of fractional time-delay systems in a noisy environment, by applying a cross-convolution approach. Besides, a filtering methodology is incorporated with the proposed approach to enhance its efficacy. In addition, this paper presents novel theories on convolution in the field of fractional calculus. Finally, the performance of the proposed approach is demonstrated by numerical simulations. [ABSTRACT FROM AUTHOR]

In the case of multicollinearity, biased estimators are always introduced to correct the least squares estimator. In this paper, we propose a new biased estimator for the restricted linear model. The properties of the new estimator and its superiority over the restricted least squares estimator in terms of the mean square error and Pitman closeness criterion are theoretically analysed. Furthermore, we optimize and verify the feasibility of the new estimator using a numerical simulation. [ABSTRACT FROM AUTHOR]

This paper presents general theoretical studies on asymptotic convergence rate (ACR) for finite dimensional optimization. Given the continuous problem function and discrete time stochastic optimization process, the ACR is the optimal constant for control of the asymptotic behaviour of the expected approximation errors. Under general assumptions, condition ACR < 1 implies the linear behaviour of the expected time of hitting the ε - optimal sublevel set with ε → 0 + and determines the upper bound for the convergence rate of the trajectories of the process. This paper provides general characterization of ACR and, in particular, shows that some algorithms cannot converge linearly fast for any nontrivial continuous optimization problem. The relation between asymptotic convergence rate in the objective space and asymptotic convergence rate in the search space is provided. Examples and numerical simulations with use of a (1+1) self-adaptive evolution strategy and other algorithms are presented. [ABSTRACT FROM AUTHOR]

Background: Shortages of mechanical ventilation have become a constant problem in Emergency Departments (EDs), thereby affecting the timely deployment of medical interventions that counteract the severe health complications experienced during respiratory disease seasons. It is then necessary to count on agile and robust methodological approaches predicting the expected demand loads to EDs while supporting the timely allocation of ventilators. In this paper, we propose an integration of Artificial Intelligence (AI) and Discrete-event Simulation (DES) to design effective interventions ensuring the high availability of ventilators for patients needing these devices. Methods: First, we applied Random Forest (RF) to estimate the mechanical ventilation probability of respiratory-affected patients entering the emergency wards. Second, we introduced the RF predictions into a DES model to diagnose the response of EDs in terms of mechanical ventilator availability. Lately, we pretested two different interventions suggested by decision-makers to address the scarcity of this resource. A case study in a European hospital group was used to validate the proposed methodology. Results: The number of patients in the training cohort was 734, while the test group comprised 315. The sensitivity of the AI model was 93.08% (95% confidence interval, [88.46 − 96.26%]), whilst the specificity was 85.45% [77.45 − 91.45%]. On the other hand, the positive and negative predictive values were 91.62% (86.75 − 95.13%) and 87.85% (80.12 − 93.36%). Also, the Receiver Operator Characteristic (ROC) curve plot was 95.00% (89.25 − 100%). Finally, the median waiting time for mechanical ventilation was decreased by 17.48% after implementing a new resource capacity strategy. Conclusions: Combining AI and DES helps healthcare decision-makers to elucidate interventions shortening the waiting times for mechanical ventilators in EDs during respiratory disease epidemics and pandemics. [ABSTRACT FROM AUTHOR]

In this paper, the fixed-time pinning synchronization problem of an intermittently coupled complex network is investigated. An intermittently coupled complex network with delay is presented for the first time. A new fixed-time stability lemma is developed, which is less conservative than the existing results. A more economical controller is designed under intermittent pinning control strategy. Sufficient conditions are developed to realize fixed-time synchronization. Numerical simulations are conducted to verify the effectiveness and feasibility of the obtained results. [ABSTRACT FROM AUTHOR]

Multi-frame image super-resolution reconstruction focuses on obtaining a high-resolution (HR) image from a low-resolution image. Since the super-resolution problem is ill-posed, it is frequent to use regularization techniques. However, the choice of these regularization terms is not always direct. Generally, every term should contain some prior knowledge over the image, that is why it plays an important role in increasing the quality of the restored HR image. In this paper, we propose a total variable-order variation based-regularization to provide a natural-looking and an effective reconstruction of the desired HR image. We also present some existence and uniqueness results of our proposed model. The alternating direction method of multipliers algorithm is employed to implement the numerical simulations. Experimental results reveal that the proposed approach can reconstruct and recover high-quality results visually and quantitatively. [ABSTRACT FROM AUTHOR]

Empirical and probabilistic risk analysis methods can relatively accurately predict the seismic vulnerability of reinforced concrete (RC) structures. Using various intensity measures to estimate and forecast the seismic hazard of RC structures can contribute to the development of typical structural seismic resilience and vulnerability models. However, traditional empirical and analytical vulnerability studies rely more on field observation data and seismic risk algorithms and less on numerical simulation analysis for validation and optimization, resulting in limitations and fuzziness in the accuracy of the developed structural risk models. To explore the damage modes of RC frame structures under different intensities, this paper innovatively combines numerical model algorithms with empirical vulnerability methods to conduct empirical vulnerability and numerical simulation analyses on RC structures. Using probability statistics and nonlinear regression analysis methods, a prediction model for estimating the fragility of RC structures was proposed, and 858 RC structure damage samples from a typical city (Dujiangyan) during the Wenchuan earthquake in China on May 12, 2008, were used for model verification and comparative analysis. Using seismic response analysis theory, 901,530 acceleration records of the Wenchuan earthquake detected by eight actual seismic stations were selected, and nonlinear dynamic time history analysis was conducted. A four-story RC structural model was established using finite element software, and numerical simulation analysis was conducted on the model using 117,863 real earthquake acceleration data points obtained from actual monitoring stations during the Wenchuan earthquake. The acceleration time history curves and incremental dynamic analysis curves of the RC structure under different intensity measures were generated. By combining the moire algorithm and numerical simulation technology, damage stress clouds of steel bars and concrete under different intensity measures were generated, and the accuracy of the developed empirical vulnerability model was verified via numerical simulation results. [ABSTRACT FROM AUTHOR]

The process of heat transfer is one of the most important issues in the food industry and plays a crucial role in the storage of frozen foods. The main objective in this field is to extend the storage time, which can be achieved by limiting the heat transfer between the ambient air and the frozen food product. In this paper, the authors applied a numerical model of the phase change process to simulate the freezing and thawing process of a package wrapped with compressible multilayer polymer thermal insulation. The model was solved in COMSOL Multiphysics program and verified with experimental results with satisfactory agreement. Based on the performed simulations and experiments, it was proved that the freezing time of the tylose package is almost the same regardless of the applied film, while the thawing time of the package strongly depends on the type of film—transparent, opaque or metallized. The use of transparent film allows to extend the maximum thawing time of food products by 2 times, the use of opaque film—by about 3.7 times, and the use of metallized film—by about 4.1 times. [ABSTRACT FROM AUTHOR]

The scale of propagation of hydraulic fractures in deep shale is closely related to the effect of stimulation. In general, the most common means of revealing hydraulic fracture propagation rules are laboratory hydraulic fracture physical simulation experiments and numerical simulation. However, the former is difficult to meet the real shale reservoir environment, and the latter research focuses mostly on fracturing technology and the interaction mechanism between hydraulic fractures and natural fractures, both of which do not consider the influence of temperature effect on hydraulic fracture propagation. In this paper, the hydraulic fracturing process is divided into two stages (thermal shock and hydraulic fracture propagation). Based on the cohesive zone method, a coupled simulation method for sequential fracturing of deep shale is proposed. The effects of different temperatures, thermal shock rates, and times on the scale of thermal fractures are analyzed. As well as the effects of horizontal stress difference and pumping displacement on the propagation rule of hydraulic fractures. The results show that the temperature difference and the thermal shock times determine the size and density of thermal fractures in the surrounding rock of the borehole, and the number of thermal fractures increases by 96.5% with the increase of temperature difference. Thermal fractures dominate the initiation direction and propagation path of hydraulic fractures. The main hydraulic fracture width can be increased by 150% and the length can be increased by 46.3% by increasing the displacement; the secondary fracture length can be increased by 148.7% by increasing the thermal shock times. This study can provide some inspiration for the development of deep shale by improving the complexity of hydraulic fractures. [ABSTRACT FROM AUTHOR]

The nozzle structure parameters of a liquid-gas ejector have an important effect on the performance of the ejector. In this paper, a numerical simulation model of a liquid-gas ejector was developed. To optimize the gas induction and mixing performance of the ejector, the effect of the nozzle structure on the flow mixing characteristics inside the liquid-gas ejector is investigated. The rationality of the numerical simulation was verified by using the experimental equipment, and the maximum relative error between the experimental and simulated data was 9.72%, which proved the reliability of the numerical simulation. The results show that: conical, folded line, and arc-shaped three different shapes of the nozzle, which the conical nozzle has the best ability to induct gas. The injection coefficient will decrease gradually with the increase of nozzle length, and the injection coefficient will increase with the increase of nozzle outlet straight section length, etc. The research results of this paper can be used to improve the gas induction and mixing performance of the liquid-gas ejector, and play an important guiding role in the design optimization of the ejector. [ABSTRACT FROM AUTHOR]

In this paper, we present a network-based optimization model describing a closed-loop supply chain for the provision of 5G network slices on demand to users and devices on the ground. The three-tier supply chain network consists of a fleet of pre-existing UAVs, to which others can be added, managed by a fleet of UAV controllers, whose purpose is to perform services requested by users and devices on the ground. The aim of this paper is to provide a constrained optimization problem through which the providers' profits are maximized, determining the global optimal distributions of request flows, the global optimal distributions of executed services and the optimal reliability level of pre-existing UAVs of the fleet. We also derive the associated Variational inequality formulation of the problem and, finally, a numerical simulation is performed to validate the effectiveness of the model. [ABSTRACT FROM AUTHOR]

The present work is a numerical follow-up on our published experimental paper on shock ignition of aluminium particle clouds in the low-temperature regime. The in-house multi-phase regularized smoothed particle hydrodynamics (MP-RSPH) code is used to perform numerical simulations with an increasing degree of complexity, looking at single-phase, inert, and reactive particles in separate simulations. The first part of the paper gives a short description of the additional physics added to the code. Based on the experimental results, the numerical code is then used to estimate the particle temperature at the time of ignition. Results from simulations with three different numerical descriptions, the diffusive, kinetic, and total burn rates, are then compared to the experimental results. The two diffusive burn rate simulations (K &H and O &H) show the best fit to the experimental results. The burn rate formula based on our experimental data (O &H) is preferred, since it has the gas temperature dependency included and does not require additional parameter adjustments. The results from the numerical simulations support the theory that the observed aluminium particle cloud burning process is diffusive, as indicated in the experimental paper. [ABSTRACT FROM AUTHOR]

Nick Bostrom's "simulation argument" purports to show that if it is possible to create and run a vast number of computer simulations indistinguishable from the reality we are living in, then it is highly probable that we are already living in a computer simulation. However, the simulation argument requires a modification to escape the undermining implications of the scepticism it implies, as argued by Birch. The present paper shows that, even if the modified simulation argument is valid, still it is unsound since it relies on the indistinguishability assumption that even in principle cannot be tested. To account for the unsoundness of the simulation argument, the present paper draws on John Woods' theory of fiction, to expose structural similarities between general fiction and the simulation argument. Though the simulation argument is unsound, it seems persuasive, because the argument immerses the reader in a fictive world with the help of tacit assumptions, leveraging just enough common sense to remain compelling while covering over an untestable premise. Simultaneously with the critique of Bostrom's argument, Chalmers' argument for the matrix hypothesis is assessed on similar criteria. In either case, both arguments rely on an accumulation of assumptions, both implicit and explicit, hiding the premises that are untestable in principle. [ABSTRACT FROM AUTHOR]

This paper investigates the global Mittag-Leffler stability of memristor-based fractional-order neural networks with mixed time-delay and impulsive. Firstly, based on assumptions, we get a Lemma about distributed delay, which is used to deal with the problems in this paper. Secondly, with the help of contraction mapping principle, the existence and uniqueness of the solution of the system are proved in this paper. Finally, this paper obtains a new sufficient condition which ensures the system globally Mittag-Leffler stable. Numerical simulations are used to verify the correctness and validity of the results in this paper. [ABSTRACT FROM AUTHOR]

Unlike the known modulation method, the formant-modulation method for the evaluation of speech intelligibility allows the evaluation of not only the speech transmission index but also the articulation index. This paper presents the results of a study of the accuracy of speech transmission index evaluation using the full and rapid variants of the formant-modulation method. The study is carried out by the computer simulation method for two cases, namely, the case of the predominant effect of noise interference and the combined effect of noise and reverberation in a room of medium volume. Dependences of the systematic and random components of the estimation error of speech transmission index on the duration of the test signal and signal-to-noise ratio are obtained. It is shown that although the fast version of the formant-modulation method is 4–5 times inferior to the full version in terms of measurement accuracy of the speech transmission index, the desired estimation accuracy can be achieved if the duration of the test signal is sufficiently long. In particular, the bias and standard deviation of the estimate of the speech transmission index obtained by the fast formant modulation method do not exceed 0.03 and 0.014, respectively, for the test signal duration of 16 s. [ABSTRACT FROM AUTHOR]

Separable multi-block convex optimization problem appears in many mathematical and engineering fields. In the first part of this paper, we propose an inertial proximal ADMM to solve a linearly constrained separable multi-block convex optimization problem, and we show that the proposed inertial proximal ADMM has global convergence under mild assumptions on the regularization matrices. Affine phase retrieval arises in holography, data separation and phaseless sampling, and it is also considered as a nonhomogeneous version of phase retrieval, which has received considerable attention in recent years. Inspired by convex relaxation of vector sparsity and matrix rank in compressive sensing and by phase lifting in phase retrieval, in the second part of this paper, we introduce a compressive affine phase retrieval via lifting approach to connect affine phase retrieval with multi-block convex optimization, and then based on the proposed inertial proximal ADMM for 3-block convex optimization, we propose an algorithm to recover sparse real signals from their (noisy) affine quadratic measurements. Our numerical simulations show that the proposed algorithm has satisfactory performance for affine phase retrieval of sparse real signals. [ABSTRACT FROM AUTHOR]

With the continuous expansion of computer system simulation applications, the dynamic system modeling problems that people face have become more and more complex. This paper mainly studies dynamic system simulation models and algorithms based on artificial neural networks. This article mainly focuses on some practical problems of dynamic system simulation, and studies the artificial neural network model and corresponding algorithm suitable for dynamic system modeling. First, it summarizes the existing artificial neural network simulation models of dynamic systems: multi-layer feedforward network relationship model without feedback, recursive network relationship model with feedback, and their network topology diagrams are drawn. Secondly, a quantum genetic algorithm is proposed to optimize the parameters of artificial neural networks and feedforward process neural networks. To achieve the preprocessing of the parameters. Next, based on the analysis and research of BP neural network theory, this paper comprehensively compares the neural network models established under various network structures and algorithms, and establishes the simulation model based on the BP neural network monitoring data system, and compares the results with the monitoring data obtained in the field. The hidden layer of neural network with 4 and 6 nodes will increase the convergence step. When the number of nodes is 10 and 12, the convergence rate may reach 46 steps. This shows that if the non-display layer with different number of nodes in the same layer is selected for the same system simulation model based on artificial neural network, the repetition number of convergence steps of the prediction model will be different. [ABSTRACT FROM AUTHOR]

In this paper, thin-walled aluminum alloy parts were fabricated using electromagnetic incremental forming with an elastic cushion. The effect of the thickness of the elastic cushion and the discharge voltage on the skin-forming quality is analyzed using numerical simulation. When the discharge voltage is 6 kV, the springback of the sheet decreases with increasing cushion thickness. However, when the cushion thickness increases to 15 mm, the sheet surface produces a 0.78-mm bulge. When, however, a 10-mm-thick cushion is used, the springback of the sheet decreases with increasing discharge voltage. On the other hand, when the discharge voltage is 8 kV, the surface of the plate produces a 1.14-mm bulge, which makes the surface not smooth. Therefore, the optimal process parameters in this paper are a 7-kV discharge voltage and a 10-mm cushion thickness. Moreover, the springback of the sheet metal can be greatly reduced after discharging six times at different positions. Based on the optimum process parameters, which are determined by the numerical simulation, experimental testing is performed. The experimental results are consistent with the simulation. [ABSTRACT FROM AUTHOR]

The work described in this paper is concerned with providing a rational asymptotic analysis of the wrinkling bifurcation experienced by a thin elastic hemispherical segment subjected to vertical tensile forces on its upper rim. This is achieved by considering the interplay between two boundary layers and matching the corresponding solutions associated with each separate region. Our key result is a four-term asymptotic formula for the critical load in terms of a small parameter proportional to the ratio between the thickness and the radius of the shell. Comparisons of this formula with direct numerical simulations provide further insight into the range of validity of the results derived herein. [ABSTRACT FROM AUTHOR]

Twenty papers on the study of tsunamis are included in Volume III of the PAGEOPH topical issue “Global Tsunami Science: Past and Future”. Volume I of this topical issue was published as PAGEOPH, vol. 173, No. 12, 2016 and Volume II as PAGEOPH, vol. 174, No. 8, 2017. Two papers in Volume III focus on specific details of the 2009 Samoa and the 1923 northern Kamchatka tsunamis; they are followed by three papers related to tsunami hazard assessment for three different regions of the world oceans: South Africa, Pacific coast of Mexico and the northwestern part of the Indian Ocean. The next six papers are on various aspects of tsunami hydrodynamics and numerical modelling, including tsunami edge waves, resonant behaviour of compressible water layer during tsunamigenic earthquakes, dispersive properties of seismic and volcanically generated tsunami waves, tsunami runup on a vertical wall and influence of earthquake rupture velocity on maximum tsunami runup. Four papers discuss problems of tsunami warning and real-time forecasting for Central America, the Mediterranean coast of France, the coast of Peru, and some general problems regarding the optimum use of the DART buoy network for effective real-time tsunami warning in the Pacific Ocean. Two papers describe historical and paleotsunami studies in the Russian Far East. The final set of three papers importantly investigates tsunamis generated by non-seismic sources: asteroid airburst and meteorological disturbances. Collectively, this volume highlights contemporary trends in global tsunami research, both fundamental and applied toward hazard assessment and mitigation. [ABSTRACT FROM AUTHOR]

This paper proposes a theoretical model of the control and perception mechanism in human balance. Human balance perception is evaluated by the subjective upright posture, the posture at which a person does not feel he/she is at an incline. Our balance experiments in the seated posture showed that the subjective upright posture changed after the balancing task where the participants needed to incline to maintain their balance. This paper aimed to explain this adaptive phenomenon by reproducing the experimental results using computer simulations. Hypothesizing that "humans gradually come to recognize the posture they need to take to maintain their balance as being upright," an adaptation rule for subjective upright posture is defined, so that it approaches the averaged posture in the period of the balancing task. For the balance control, center of pressure feedback is adopted. As a result, the similar changes in subjective upright posture are simulated with a two-link model with a base link, implying that our hypothesis is one possible explanation on the mechanism for human balance control and perception. [ABSTRACT FROM AUTHOR]

As cities have grown, conductor rail power supplies have been widely used in the field of urban rail transit. In order to improve the running performance of trains and reduce the occurrence of accidents, it is necessary to understand the vibration of shoegear-rail system under different initial contact forces and explore the dynamic performance of shoegear-rail system. Therefore, according to the structure of shoegear-rail system, a coupling model of shoegear-rail system is established in this paper. On the basis of the model, the numerical simulation of the shoegear-rail system under different initial contact forces is carried out, and finally the vibration data of the shoegear-rail system under different initial contact forces are obtained. The results show that with the increase of initial contact force in the range of 70–160 N, the vibration amplitude of the electric shoegear and the fluctuation amplitude of the contact force increase, but the maximum absolute shear force value of the conductor rail decreases. It indicates that the lower initial contact force, the better the performance of shoegear-rail system. [ABSTRACT FROM AUTHOR]

Mobile manipulator robots that combine mobile platforms and robotic arms have been attracting considerable attention in recent years. In this paper, the motion control problem of the mobile manipulator system is considered with the following proposed control strategy. Firstly, a decoupled dynamic model is created to increase operation safety and to reduce complexity such that the independent controllers can be designed for the mobile system and the manipulator system. Subsequently, an effective reference trajectory generator is proposed to guide the mobile manipulator systems to the proper position for the manipulation being able to grip the target. Thereafter, the fuzzy controllers are designed for the mobile system to eliminate the tracking error and for the manipulator system to accomplish the gripping mission. The stability of the mobile manipulator control system can be guaranteed by the Lyapunov theory. Finally, the numerical simulations are given to demonstrate the effectiveness of the proposed approach. From the simulation results, it can be seen that this paper as well as other compared methods have good control response in case of small controller gain, in which the convergence time are about 4–5 s. However, by increasing the controller gain to improve the control response, the other methods will make the system unstable or the controller output will produce a large amount of chattering. The proposed controller in this paper can not only decrease the convergence time, from 5 to 3 s, but also provide a smooth control response. [ABSTRACT FROM AUTHOR]

The derivation of pseudorandom number generation (PRNG) from the Josephson junction (JJ) stimulated by the Wien bridge oscillator (JJSWBO) and its microcontroller validation is given in this paper. Via the numerical investigations of the JJSWBO, the encyclopedic dynamical maps in different coordinate spaces constituting the system's parameters explicitly elaborate the global behaviour of the system presenting the greatest Lyapunov exponents (GLE). Chaotic behaviours were captured for GLE greater than zero and periodic behaviours for GLE less than zero. Further, bifurcation characteristics expose monostable and bistable periodic oscillations, bistable periodic doubling route to bistable chaos, interceptions of bistable regular behaviours and bistable chaotic presentations, coexisting attractors, monostable chaotic dynamics and intermittency phenomenon. The microcontroller validation (MCV) of the JJSWBO is presented to validate the numerical simulation results. From the chaotic equations describing JJSWBO, a PRNG with a linear feedback shift register (LFSR) as a post-processing unit is designed. The randomness of the generated binary data from the proposed JJSWBO-based PRNG is successfully tested by using the NIST 800-22 test suite. This result helps to confirm the suitability of the JJSWBO for encryption schemes and other chaos-based applications. [ABSTRACT FROM AUTHOR]

The dynamic characteristics of vehicular ad hoc networks (VANETs) demand reliable and secure communication over wireless media. However, there are significant contradictions in autonomous vehicular systems related to security and privacy. Furthermore, VANETs require seamless data transmission to exchange time-critical data about accidents and traffic. Therefore, VANETs require secure seamless data transmission mechanisms to provide secure reliable communication without communication interruption to exchange time-critical data between vehicles. This paper proposes an Enhanced Location-Aided Ant colony Routing (ELAACR) for VANETs to achieve seamless secure data transmission. The proposed ELAACR is a two-fold scheme in which Phase 1 implements Location-Aided Key Management (LAKM) and Phase 2 implements Ant Colony Routing (ACR). An ACR combined with an LAKM pattern for offering secure and reliable communication. The LAKM scheme works based on the group signature concept to construct a secure network, and an ACR is used to find an efficient secure shortest path for seamless data transmission. The proposed work is simulated in Network Simulator (NS 2.35). By using an efficient and secure shortest path with secure seamless data transmission, the proposed ELAACR achieves an average throughput (T) of 640 Kbps, packet loss rate (PLR) of 0.018%, packet delivery ratio (PDR) of 98.5%, overhead (OH) of 0.157%, and 0.16 s end-to-end delay (EED) compared to Enhanced Hybrid Ant Colony Optimization Routing Protocol (EHACORP) and Fuzzy Based Ant Colony Optimization (F-ANT). The simulation results show that the proposed ELAACR registers better performance in all aspects compared to the existing EHACORP and F-ANT. [ABSTRACT FROM AUTHOR]

The freezing damage of rock tunnels in cold region involves ice-water phase change and complicated interaction of Thermo–Hydro–Mechanical (THM) field. Taking the fractured rock mass of cold region tunnels as research subject, the THM coupling model of cold region tunnels was established, which is based on the seepage mechanics, heat transfer theory, damage mechanics and equivalent continuum theory. This model could reflect the anisotropic properties of deformation, water migration and heat transfer caused by the initial fracture of rock mass. The construction and operation processes of a rock tunnel in cold region were simulated, and results were compared with the measured value and predecessor's achievements. It shows that proposed model could reflect the anisotropic property of surrounding rock and the simulated deformation and stress are not symmetrical. Compared with the literature, the calculated results in this paper are closer to the measured values. The insulating layer has a significant effect on the stress of the supporting structures. The maximum tension stress of the lining is 4.5 times as that without insulating layer, and the lining will be destroyed for the overlarge tension stress. [ABSTRACT FROM AUTHOR]

Burden is one of the major influencing blast design parameters which should be optimised for the extraction of narrow vein ore bodies. Numerical simulation-based approach has been used for the optimisation of burden in this paper. Different models were prepared under varying parametric conditions including width of the vein, blasthole diameter and burden. The RHT concrete constitutive model was used for the analysis of damage contour. The volume of the excavated rock along the free face (EV) was quantified from the model output in all the scenario. The study showed that EV initially increases with the increase in burden for a particular width of vein. Furthermore, EV starts decreasing after a point termed as pivot point. The value of burden at this pivot point was considered as optimal in this study. The best fit curve between EV and burden for three blasthole diameter and seven different width of vein were plotted. In all instances, the outputs of the model followed the second-degree polynomial equation. The study also suggests that the optimum burden reduces with the increase in the width of the vein. It has also been found that the optimum burden follows power trend with the increase in width of the ore body irrespective of blasthole diameter. Based on the optimum burden obtained from the output of simulation along with different blasthole diameter and width of the ore body, an empirical relationship has been established. The developed empirical relationship has a good agreement with the experimental trial data. Highlights: Numerical simulation technique has been used in this paper for the optimisation of burden while extraction of narrow vein stopes. The study suggest that the relation of volume of the excavated rock along the free face and burden is second-degree polynomial in nature. It has been found that the optimum burden for narrow vein is higher as compared to wider width ore body. Study also suggest that optimum burden follows power trend with the increase in width of ore body. The influence of width of the ore body in the selection of burden vanishes after certain width of ore body as per the observation of model output. [ABSTRACT FROM AUTHOR]

In this paper, an optimal nonlinear attitude controller is designed and implemented as hardware in the loop for a spacecraft simulator under various failures of reaction wheels. The proposed controller is developed in the closed form based on predicting the nonlinear continuous responses of spacecraft simulator. The special case of the controller when all uncertainties are ignored leads to feedback linearization. However, the stability of the controller in the presence of parametric uncertainties and unmodeled dynamics of the platform is analyzed, and the effect of the prediction time on the boundedness of system responses is presented. A redundant reaction wheel is located in the platform to compensate for failures of three main reaction wheels. How to distribute torque between healthy wheels under different types of failure including stuck and oscillatory failures is addressed and experimentally implemented. The laboratory results that are consistent with computer simulations show the accuracy and validity of the designed controller. It is seen that the spacecraft attitude converges in a limited time in the presence of system uncertainties and actuator failures. [ABSTRACT FROM AUTHOR]

Equation-free modeling aims at extracting low-dimensional macroscopic dynamics from complex high-dimensional systems that govern the evolution of microscopic states. This algorithm relies on lifting and restriction operators that map macroscopic states to microscopic states and vice versa. Combined with simulations of the microscopic state, this algorithm can be used to apply Newton solvers to the implicitly defined low-dimensional macroscopic system or solve it more efficiently using direct numerical simulations. The key challenge is the construction of the lifting and restrictions operators that usually require a priori insight into the underlying application. In this paper, we design an application-independent algorithm that uses diffusion maps to construct these operators from simulation data. Code is available at https://doi.org/10.5281/zenodo.5793299. [ABSTRACT FROM AUTHOR]

Purpose: This paper proposes a quasi-zero-stiffness (QZS) vibration isolator with asymmetric stiffness and geometric nonlinear damping and investigates the effect of nonlinear damping on its vibration isolation performance. In addition, the QZS isolator possesses a large support capacity by introducing the torsion bar spring as positive stiffness component. Methods: The motion equation of the proposed QZS isolator under harmonic excitation can be described as Helmholtz–Duffing equation. The frequency response curves and unstable regions of the proposed isolator are approximately solved by harmonic balance method (HBM). The nonlinear damping characteristics and their effects on the transmissibility of the isolator are studied by approximate analysis and fourth-order Runge–Kutta numerical simulation. Results: The response and unstable region of the system under different nonlinear damping are solved theoretically and are in good agreement with the numerical simulation results. Conclusion: The results indicate that the increase of geometric nonlinear damping can achieve better high-frequency vibration isolation performance while suppressing the primary resonance than the vertical linear damping, which means the nonlinear damping makes the proposed QZS isolator with asymmetric stiffness show good full-band vibration isolation performance. Moreover, the suitable situation is maintaining a certain vertical damping ratio to suppress the subharmonic response more efficiently. [ABSTRACT FROM AUTHOR]

Fabrizio and Caputo suggested an extraordinary definition of fractional derivative, which has been used in many fields. The SIDARTHE infectious disease model with regard to COVID-19 is studied by the new notion in this paper. Making use of the Banach fixed point theorem, the existence and uniqueness of the model's solution are demonstrated. Then, an efficient method is utilized to deduce the iterative scheme. Finally, some numerical simulations of the model under various fractional orders and parameters are shown. From the computed result, we can see that it not only supports the theoretical demonstration, but also has an intensive insight into the characteristics of the model. [ABSTRACT FROM AUTHOR]

CitcomCu is a numerical simulation software for mantle convection in the field of geodynamics, which can simulate thermo-chemical convection in a three-dimensional domain. Due to the increasing demand for high-precision simulations and larger application scales, larger-scale computing systems are needed to solve this problem. However, the parallel efficiency of CitcomCu on large-scale heterogeneous parallel computing systems is difficult to improve, especially it cannot adapt to the current mainstream heterogeneous high-performance computing architecture with CPUs and accelerators. In this paper, we propose an geodynamics numerical simulation parallel computing framework using heterogeneous computing architecture based on the Tianhe new-generation high-performance computer. Firstly, the data partitioning mode of CitcomCu was optimized based on the large-scale heterogeneous computing architecture to reduce the overall communication overhead. Secondly, the iterative solution algorithm of CitcomCu was improved to speed up the solution process. Finally, the NEON instruction set based on SIMD is used for the sparse matrix operations in the solution process to improve parallel efficiency. Based on our parallel computing framework, the optimized CitcomCu was deployed and tested on the Tianhe new-generation high-performance computer. Experimental data showed that the performance of the optimized program was 3.3975 times higher than that of the unoptimized program on a single node. Compared with 50,000 computational cores, the parallel efficiency of the unoptimized program on one million computational cores was 36.75%, while the parallel efficiency of the optimized program was improved by 16.22% and reached 42.71%. In addition, the optimized program can be executed on 40 million computational cores, with a parallel efficiency of 36.54%. [ABSTRACT FROM AUTHOR]

The paper proposes a methodology for mathematical modeling of the phased development of nodes and transport routes in a hierarchical network with multicommodity discrete flows of correspondences based on solving the problems of optimizing its structure and distribution of flows. As a rule, such networks consist of a decentralized mainline network and networks in the internal service areas of mainline nodes. In a multicommodity network, each node can exchange correspondence (products, goods, cargo, messages) with the other nodes. Correspondence is characterized by a source node, a sink node, and a quantity, which for data transmission networks is given by the number of bytes, kilobytes, etc., and for transport networks by the number of cargo units in a package of uniform size. In the mainline network, all correspondences are transmitted via communication channels or transported by vehicles in transport units of a given size (capacity, volume). The authors considered the main postulates of generating a mathematical model of the perspective development of mainline network. They presented a method of mathematical modeling of the phased development of nodes and transport routes, which includes, for each stage of development, the forecasting of data and network parameters, solving the problem of packing correspondence and choosing the structure of the network, and solving the problem of distribution and routing of transport unit flows. [ABSTRACT FROM AUTHOR]

This paper proposes a new flexible and microscale roll gap control technology to obtain a stronger strip flatness control ability. According to the principle of microscale roll gap control technology, an electromagnetic control rolling mill with the function of roll profile control and large diameter ratio rolling is designed and built. To analyze the flatness control ability, a comprehensive finite element model (FEM) is established, and an indentation experiment and a rolling experiment are carried out. The simulation results show that under different rolling forces and tensions, the average quadratic crown control ability is more than 40 μm, and the average quartic crown control ability is more than − 3 μm. The control ability increment of the quadratic crown is greater than that of the quartic crown. In the indentation experiment, a stable roll profile can be achieved by PID control after reaching the target roll profile. Increasing the regulation amount can change the strip crown from positive to negative. Even under high rolling force conditions, microscale roll gap control technology can also realize a strip crown adjustment of 19.5 to 0.5 μm. Moreover, this technology can adjust the strip shape from edge waves to non-waves and middle waves in the rolling experiment. In this paper, the feasibility of using this technology to adjust the roll gap shape has been verified, and we demonstrate that the roll gap control goal of uniform transverse size distribution can be achieved. [ABSTRACT FROM AUTHOR]

In this paper, we study a three-dimensional system of differential equations which is a generalization of the system introduced by Yu and Wang (Eng Technol Appl Sci Res 3:352–358, 2013), a continuation of the study of chaotic attractors [see Yu and Wang (Eng Tech Appl Sci Res 2:209–215, 2012)]. We show that these systems admit a zero-Hopf non-isolated equilibrium point at the origin and prove the existence of a limit cycle emanating from it. We illustrate our results with some numerical simulations. [ABSTRACT FROM AUTHOR]

Multi-stage hot forging is widely used to produce complex forged products in inFdustry. Flash after the forging should always be minimized for the material saving, and it is important to determine the preform shape minimizing the flash. The process parameters in multi-stage hot forging such as the billet temperature and the stroke have also an influence on the product quality as well as the flash, but they are still determined by a trial-and-error method. In this paper, multi-objective design optimization in three-dimensional multi-stage hot forging is numerically performed so as to minimize both the flash and the distribution of equivalent strain. The preform shape and the process parameters such as the billet temperature, the die temperature and the stroke are optimized. The three-dimensional numerical simulation is computationally so expensive that sequential approximate optimization that response surface is repeatedly constructed and optimized is adopted to identify the pareto-frontier between the flash and the distribution of equivalent strain. It is found from the numerical result that 60% reduction of flash can be achieved, compared to the conventional preform shape. In addition, the total forging energy considering the multi-stage hot forging is reduced. It is confirmed through the numerical result that the proposed approach is valid to determine the optimal preform shape and process parameters in multi-stage hot forging. [ABSTRACT FROM AUTHOR]

Through the annals of time, writing has slowly scrawled its way from the painted surfaces of stone walls to the grooves of inscriptions to the strokes of quill, pen, and ink. While we still inscribe stone (tombstones, monuments) and we continue to write on skin (tattoos abound), our quotidian method of writing on paper is increasingly abandoned in favor of the quick-to-generate digital text. And even though the stone-inscribed text of epigraphy offers demonstrably better permanence than that of writing on skin and paper—even better than that of the memory system of the modern computer (Bollacker in Am Sci 98:106, 2010)—this field of study has also made the digital leap. Today's scholarly analyses of epigraphic content increasingly rely on high-tech approaches involving data science and computer models. This essay discusses how advances in a number of exciting technologies are enabling the digital analysis of epigraphic texts and accelerating the ability of scholars to preserve, renew, and reinvigorate the study of the inscriptions that remain from throughout history. [ABSTRACT FROM AUTHOR]

The simultaneous variation of slope height and slope feet angle is a significant feature of three-dimensional slopes. Expanding the safety factor of two-dimensional slopes to three-dimensional is the most popular approach for calculating the safety factor of three-dimensional slopes. In this approach, however, the influence of three-dimensional effects is seldom considered. To correct this oversight, a novel calculation method for the safety factor of three-dimensional homogeneous cohesive soil slopes is proposed, involving 2 key parameters: the variation rates of slope height and slope feet angle. The stress state of the soil column on its bottom surface is simplified by the synthesis vectors of the tangent and normal vectors, which are determined by different shovel angles on each side of the soil column. By using a three-dimensional limit equilibrium method with a shear exertion coefficient, the safety factor of a cohesive soil pit slope at the site of a tunnel entrance, with synchronously-varied height and feet angle, in the North Hubei Water Transfer Engineering is calculated. The calculation results are then compared with those obtained by existing literature and numerical simulation method. This comparison reveals that the deviation is small, and the shape of sliding surface is basically the same as that of numerical simulation method, which reflects the strong rationality of the method in this paper. Furthermore, by analyzing the impact of 2 key parameters, it can be seen that the slope safety factor Fs may have same values under different k1 and k2 combinations. And meanwhile, the three-dimensional characteristics of slopes in different degrees may have opposite effects on Fs. [ABSTRACT FROM AUTHOR]

Geotechnical Seismic Isolation (GSI) technique has been herein discussed for several bridge configurations in order to assess the seismic vulnerability. Comparison between traditional base isolation (BI) and GSI technique has been carried out by considering a cost assessment evaluation. The effects of soil structure interaction (SSI) were considered by performing advanced numerical simulations that consider the role of soil deformability. Overcoming most of the existing literature, this paper proposes comprehensive 3D models (soil + isolation + bridge) by performing OpenSees that implements non-linear mechanisms of the soil and may realistically assess the induced damage caused by the mutual interaction of buckling and seismic loads. [ABSTRACT FROM AUTHOR]

This paper proposes a new image encryption algorithm using novel block-level scrambling scheme and bit-level filer diffusion technology. In order to increase the diversity of pseudo-random number generator (PRNG) and improve the security of encryption system, a new Josephus travel scheme is proposed in this paper. Then, based on the novel Josephus travel method, a novel block-level scrambling scheme and bit-vector diffusion operation are proposed to improve the encryption efficiency of the algorithm. Numerical simulation and comparison experiments shows that the proposed encryption algorithm has high security and faster encryption speed, and can resist various attacks. [ABSTRACT FROM AUTHOR]

The accumulated methane in goaf during coal mining may leak into the working face under the airflow influence, which is possibly causing disasters such as methane gas excessive at the working face and seriously threatening the mine safety. This paper first established a three-dimensional numerical model of the mining area under U-shaped ventilation, introducing the gas state equation, continuity equation, momentum equation, porosity evolution equation, and permeability evolution equation to simulate the airflow field and gas concentration field in the mining area under the natural state. The reliability of the numerical simulations is then verified by the measured air volumes at the working face. The areas in the mining area where gas is likely to accumulate are also delineated. Subsequently, the gas concentration field in goaf under the gas extraction state was theoretically simulated for different locations of large-diameter borehole. The maximum gas concentration in goaf and the gas concentration trend in the upper corner were analyzed in detail, and the critical borehole location (17.8 m from the working face) was determined as the optimum location for gas extraction from the upper corner. Finally, a gas extraction test was carried out on-site to evaluate the application effect. The results show that the measured airflow rate has a small error with the simulated results. The gas concentration in the area without gas extraction is high, with the gas concentration in the upper corner being over 1.2%, which is greater than the critical value of 0.5%. The maximum reduction in gas concentration was 43.9%, effectively reducing the gas concentration in the extraction area after employing a large borehole to extract methane gas. The gas concentration in the upper corner and the distance of the borehole from the working face are expressed as a positive exponential function. The field engineering results show that the implementation of the large borehole at a distance of less than 17.8 m from the working face can control the gas in the upper corner to less than 0.5%, effectively reducing the risk of gas in the upper corner. The numerical simulation work in this paper can provide some basic support for the design of an on-site borehole to extract gas from the mining void and reduce the gas hazard in coal mines. [ABSTRACT FROM AUTHOR]

The paper considers the question of the possibility of using differential equations in Roy's elements for numerical simulation of the motion of artificial earth satellites. An original algorithm for reducing the integration step is proposed to preserve the accuracy of simulation when the satellite passes the Earth's shadow. Using a spacecraft of GLONASS as an example, it is shown that simulation in Roy's elements is as highly efficient as in regular Lagrange's elements. [ABSTRACT FROM AUTHOR]

Edge detection is a basic problem in digital image processing. Its purpose is to detect the pixels whose gray level changes obviously in the neighborhood. The Canny edge detector is currently the most popular edge detection tool. This paper studies the specific implementation of Canny detector in the quantum computing paradigm. For Gaussian smoothing filtering and Sobel sharpening operators, we have designed a new method called "Translation, Stacking and Weighted Summation", which can make full use of the parallelism of quantum computing to accelerate its classical counterpart and avoid convolution operation. For the gradient and angle calculations required for edge detection, we design new operators such as addition, multiplication and division of signed number by introducing the binary complement description of gray-scale value. For the non-maximum suppression and double threshold processing required for edge detection, we have separately designed the quantum circuits that implement these tasks by introducing quantum complement comparators. Complexity analysis shows that the quantum Canny edge detector has exponential speedup compared to its classical counterpart. The implementation of the Canny edge detector based on quantum computing is the main contribution of this paper. The simulation on the classical computer verifies the correctness of the quantum Canny edge detection results. [ABSTRACT FROM AUTHOR]

The coupled motion of roll and pitch is noticeable when trimaran sails in oblique head waves, which will lead to negative influence on the safety and comfort of navigation. In this paper, the numerical simulation of the trimaran's motion in oblique waves was carried out by open source CFD tool OpenFOAM, and the computed motion response was analyzed to study the characteristics of the torsional rolling. The OpenFOAM-based hybrid method used in this paper was briefly introduced first, and the numerical method was validated and verified by both the grid convergence test and the comparison with experimental result. Both the amplitude and the time history of the computed motion are used for analysis, and the influence of wave steepness, wave heading and forward speed of trimaran on the characteristics of torsional rolling was investigated. The result shows that the large wave steepness and the low forward speed will lead to dangerous torsional rolling motion of trimaran in oblique waves, and the dangerous condition is mainly caused by nonlinear rolling motion; the motion state is more sensitive and changing obviously with other factors at large wave steepness wave conditions. [ABSTRACT FROM AUTHOR]

The issue about cascading failures of interdependent networks is a hot research field based on the current complex network basic theories. This paper mainly researches methods for improving robustness of interdependent networks. At first, a model of interdependent network cascading failures was established to carry out robustness analysis of three different interdependent networks including BA-BA, WS-WS and ER-ER. Then, methods for improving robustness of interdependent networks under random attacks and targeted attacks were researched respectively. (1)Under random attacks, based on the overall idea of network addition, the paper summarized four common methods for improving robustness of a simple complex network, including random addition, low-degree node addition, low-betweenness node addition and addition based on algebra connectivity. After that, according to inherent characteristics of interdependent networks, the paper put forward an interdependent network addition algorithm based on internal similarities. It is shown in cascading failure simulation calculation results of three interdependent coupling networks, that the method put forward in this paper can most effectively improve robustness of interdependent networks under random attacks. (2)Based on the overall idea of protecting key nodes under targeted attacks, the paper put forward a method for analyzing key nodes of interdependent networks based on natural connectivity. Then, under the BA-BA interdependent network, the paper analyzed this method in comparison with the commonly approved Max-Cas algorithm. It is shown in simulation calculation results that, the method put forward in this paper can more obviously improve robustness of an interdependent network under targeted attacks and can be applied flexibly. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor discusses various reports within the issue on topics related to visual computer including sketch-based modeling, character animation, and physics-based simulation.

In order to better analyze and control the micro milling process of micro ball-end milling cutter, a method combining finite element method (FEM) and regression analysis is proposed to simulate and analyze the micro cutting process of cutting edge micro-element at different axial height positions to achieve micro milling force prediction. Combining cutting edge curve equations and actual measurements establish an accurate micro ball-end milling cutter model, and discrete along the axial direction of the cutter to obtain multiple sets of cutting edge micro-element of equal thickness. In this study, a workpiece micro-element model corresponding to the axial height position of the cutting edge micro-element is established based on the actual cycloidal motion trajectory during the micro milling of the cutting edge. Finite element simulation of single-edge bevel cutting of cutting micro-elements is implemented. Based on the micro cutting force data obtained from the micro cutting simulation, regression analysis is used to obtain the cutting edge micro-element unit cutting force related to axial height and cutter rotation angle for a certain amount of feed per tooth, and then the integral summation is used to achieve the micro milling force prediction. A comparative analysis of the full slot micro milling experiments shows that the predicted micro milling forces are in good agreement with the measured values, which directly verifies the correctness and reliability of the cutting edge micro-element cutting numerical simulation and micro milling force prediction method in the paper. [ABSTRACT FROM AUTHOR]

Attapulgite has been widely used in food, chemical and building materials industries as a new mineral with a unique structure and complete application. Crushing is an essential part of the preliminary treatment of attapulgite. In general, the water content of newly excavated attapulgite is often as high as 44%. Therefore, when crushing the newly excavated attapulgite, the crusher will encounter sticking tools and agglomerating, which will lower crushing efficiency and lead to motor burning or other issues. To solve the above problems, the crusher cutter was improved by combining bionics and discrete element method in this paper, and the crushing process of attapulgite was simulated numerically. The results show that: (1) The numerical simulation results are in good agreement with the literature data; (2) bionic devices can increase the disturbance of concave soil particles and make them less likely to accumulate in the front of cutting tools; (3) the bionic tool designed with crocodile teeth has low rock breaking resistance and low energy consumption; the rock-breaking efficiency increases with teeth' angle. The bionic tool can achieve the purpose of reducing viscosity and drag, and the optimized tool structure is simple and easy to realize. In addition, the introduction of bionics will help us to improve the shortcomings of traditional machinery and improve production efficiency. [ABSTRACT FROM AUTHOR]

This paper reports a new 3D sub-quadratic Lorenz-like system and proves the existence of two pairs of heteroclinic orbits to two pairs of nontrivial equilibria and the origin, which are completely different from the existing ones to the unstable origin and a pair of stable nontrivial equilibria in the published literature. This motivates one to further explore it and dig out its other hidden dynamics: Hopf bifurcation, invariant algebraic surface, ultimate boundedness, singularly degenerate heteroclinic cycle and so on. Particularly, numerical simulation illustrates that the Lorenz-like chaotic attractors coexist with one saddle in the origin and two stable nontrivial equilibria, which are created through the broken infinitely many singularly degenerate heteroclinic cycles and explosions of normally hyperbolic stable foci E z. [ABSTRACT FROM AUTHOR]

This paper presents a coil optimization method of the ultra-deep azimuthal electromagnetic (EM) resistivity Logging While Drilling (LWD) to obtain the best parameters of the tool for formation boundary detection by theory. First, a rapid numerical simulation algorithm, i.e. the Fast Hankel Transform (FHT) method, is developed to simulate the logging responses of the layered formation. A system of double inclined coils is selected based on the response characteristics and the depth of detection (DOD) from four common coils. Simulation results demonstrated that the optimal coils are perfectly suitable for anisotropic formation. Then, the crucial parameters of the frequency and spacing of the selected coils with a DOD of 30 m are determined using the Picasso diagram. In addition, the influences of the electrical parameter of the drilling collar and resistivity anisotropy of the formation on the response are investigated. The results show that the conductivity of the drilling collar, the thickness and the resistivity anisotropy of the formation all affect the DOD. Finally, formation models with different layers are created to verify the performance and signal intensity. The results demonstrate that the optimized coils not only have a large DOD but also possess a high signal intensity, further confirming the advantages of the preferred coils. Compared with the conventional physical experiment tests, the method of coil optimization proposed in this paper is more economical and efficient. The findings of this study can help better understand the detection characteristics of the different coils, which can provide theoretical support for designing and developing a tool with the best boundary capability. [ABSTRACT FROM AUTHOR]