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Machine Learning methods are emerging as faster and efficient alternatives to numerical simulation techniques. The field of Scientific Computing has started adopting these data-driven approaches to faithfully model physical phenomena using scattered, noisy observations from coarse-grained grid-based simulations. In this paper, we investigate data-driven modelling of Bose-Einstein Condensates (BECs). In particular, we use Gaussian Processes (GPs) to model the ground state wave function of BECs as a function of scattering parameters from the dimensionless Gross Pitaveskii Equation (GPE). Experimental results illustrate the ability of GPs to accurately reproduce ground state wave functions using a limited number of data points from simulations. Consistent performance across different configurations of BECs, namely Scalar and Vectorial BECs generated under different potentials, including harmonic, double well and optical lattice potentials pronounces the versatility of our method. Comparison with existing data-driven models indicates that our model achieves similar accuracy with only a small fraction ( 1 50 th) of data points used by existing methods, in addition to modelling uncertainty from data. When used as a simulator post-training, our model generates ground state wave functions 36 × faster than Trotter Suzuki, a numerical approximation technique that uses Imaginary time evolution. Our method is quite general; with minor changes it can be applied to similar quantum many-body problems. [ABSTRACT FROM AUTHOR]

The study of landslide initiation mechanisms and dynamic process analysis is important for monitoring, predicting, and controlling landslide occurrence. A giant landslide that occurred on July 19, 2018, in Yanyuan County, Southwest China, was investigated, providing a research example. In this paper, the failure mechanism and dynamic process of the Boli landslide were analyzed using field investigations, laboratory experiments, unmanned aerial vehicle (UAV) photogrammetry, remote sensing images, hydrological calculations, and numerical simulations. The results indicated that the antecedent rainfall was not the direct factor to saturate the sliding mass. The runoff supply provided by the comb-like channel group upstream of the landslide reached 709.5 mm, which was an important hydrodynamic triggering point for accelerating the sliding mass to saturation and instability. Numerical simulation results showed that the evolution of the landslide included three stages: low-speed initiation, accelerating sliding, and flow deposition. The maximum sliding speed of the landslide occurred during the second stage and reached 39 m/s. From the source zone to the Taozi Gully, the silt content decreased from 67.9 to 40%, which was an internal particle–triggering factor of the alteration of the sliding mass from the liquefaction-resistant state to the liquefaction-prone state. The study has revealed the failure mechanism of the landslide and presented its dynamic process, which could be used to provide a reference for the study of similar landslides mainly induced by runoff supplied by such channel groups. [ABSTRACT FROM AUTHOR]

Public policies are designed to have an impact on particular societies, yet policy-oriented computer models and simulations often focus more on articulating the policies to be applied than on realistically rendering the cultural dynamics of the target society. This approach can lead to policy assessments that ignore crucial social contextual factors. For example, by leaving out distinctive moral and normative dimensions of cultural contexts in artificial societies, estimations of downstream policy effectiveness fail to account for dynamics that are fundamental in human life and central to many public policy challenges. In this paper, we supply evidence that incorporating morally salient dimensions of a culture is critically important for producing relevant and accurate evaluations of social policy when using multi-agent artificial intelligence models and simulations. [ABSTRACT FROM AUTHOR]

This paper studies a class of fractional-order systems (FOSs) and proposes control laws based on physical significance variables. Lyapunov techniques and the methods that derive from Yakubovici–Kalman–Popov Lemma are used, and the frequency criterions that ensure asymptotic stability of the physical significance variable closed-loop system are inferred. The asymptotic stability of the observer system is studied for a sector control law where the output is defined by the physical significance variables. Frequency criterions and conditions for asymptotic stability are determined. The control techniques are extended to a class of linear delay fractional-order systems and nonlinear FOS. Numerical simulations of a class of systems described by fractional-order models show the method efficiency. [ABSTRACT FROM AUTHOR]

This paper describes a numerical simulation of vibrations of an elastic rod whose height is significantly greater than its transverse dimension and which is placed perpendicularly to the external flow and rigidly mounted on a substrate. Simulation is carried out in the ANSYS software package using bidirectional coupling technology. The natural frequencies and vibration modes of the rod are calculated. The airflow structure is analyzed and its features in the vicinity of the model are described. The process of exciting the vibrations of an elastic rod under the action of an external flow is investigated and its stress-strain state is determined. Vibration modes in the direction of an incident flow and in the transverse direction are determined. It is shown that, if the first natural frequency and the vortex shedding frequency reach close values, the amplitude of the rod vibrations in the transverse direction sharply increases to a value approximately equal to 0.06 of the rod height, which is followed by natural vibrations with a constant amplitude in the transverse direction and variable amplitude in the direction of the incident flow. [ABSTRACT FROM AUTHOR]

A theoretical discussion of the discharge effects of upward lightning simulated with a fine-resolution 2D thunderstorm model is performed in this paper, and the results reveal that the estimates of the total induced charge on the upward lightning discharge channels range from 0.67 to 118.8 C, and the average value is 19.0 C, while the ratio of the induced charge on the leader channels to the total opposite-polarity charge in the discharge region ranges from 5.9% to 47.3%, with an average value of 14.7%. Moreover, the average value of the space electrostatic energy consumed by upward lightning is 1.06×109 J. The above values are lower than those related to intracloud lightning discharges. The density of the deposited opposite-polarity charge is comparable in magnitude to that of the preexisting charge in the discharge area, and the deposition of these opposite-polarity charges rapidly destroys the original space potential well in the discharge area and greatly reduces the space electric field strength. In addition, these opposite-polarity charges are redistributed with the development of thunderstorms. The space charge redistribution caused by lightning discharges partly accounts for the complexity of the charge structures in a thunderstorm, and the complexity gradually decreases with the charge neutralization process. [ABSTRACT FROM AUTHOR]

This paper addresses the issue of stability of a class of multiple unstable Cohen–Grossberg neural networks(CGNNs) under impulsive control. Some novel sufficient conditions are given to make the unstable equilibrium points of the model locally μ-stable. An example is offered to demonstrate the effectiveness of the control strategy by comprehensive computer simulations. [ABSTRACT FROM AUTHOR]

Cracking behavior of flawed samples has been extensively studied in rocks and rock-like materials using experimental and numerical approaches. However, the existing research mainly focuses on the effects of flaw length l and inclination angle α on rock mechanical behavior, a limited attention has been given to understand the role of flaw width b on crack initiation and propagation in relation to mechanical parameters of rocks. In this paper, a two-dimensional particle flow code (PFC2D)-based synthetic rock model, which is calibrated by the laboratory sandstone properties, is used to investigate the effects of flaw width on cracking behavior of single-flawed rock samples under uniaxial compression tests. Numerical simulation results show that the flaw width b has significant effects on the crack geometrical parameters (crack initiation location d and crack initiation angle θ). The values of θ and d significantly decrease with the increase of flaw width when b < 1.0 mm and their values tend to be stable with the further increase of flaw widths. It is also found that the mechanical properties (uniaxial compressive strength UCS and deformation modulus Es) of flawed rock samples are related to the crack geometrical parameters (θ and d) and the effects of flaw width on the values of UCS and Es of single-flawed rock specimens is significant when b < 1.0 mm for lower crack inclination angle (α < 60°). [ABSTRACT FROM AUTHOR]

Microscopic seepage characteristics are critical for the evaluation of tight sandstone reservoirs. In this study, a digital core approach integrating microscopic seepage simulation and CT scanning was developed to characterize microscopic seepage and fracture effectiveness (the ratio of micro-fractures that contributes to fluid flow) of tight sandstones. Numerical simulations were carried out for characterizations of tight sandstones. The results show that the axial permeability of the investigated cylindrical tight sandstone from Junggar Basin in China is 0.460 μm2, while the radial permeability is 0.3723 μm2, and the axial and radial effective fracture ratios are 0.4387 and 0.4806, respectively, indicating that cracks are not fully developed and the connectivity between micro-cracks is poor. Directional permeability that is difficult to measure by laboratory experiments can be obtained readily using the proposed method in this paper. The results provide important information for improving the exploration and development of tight sandstone reservoirs. [ABSTRACT FROM AUTHOR]

In this paper, two-dimensional (2-D) direction-of-arrival (DOA) estimation issue is investigated by constructing array model on moving platform. Based on the moving array model, we propose two improved three-parallel coprime arrays (TPCPAs), which utilize the redundancy in the physical structure of moving TPCPA (MTPCPA) and are able to generate the same virtual array as MTPCPA using much fewer sensors. Accordingly, higher sensor utilization is achieved by the proposed arrays, which can contribute to the increase in the number of degrees of freedom. Besides, with the proposed arrays, we also present a 2-D off-grid DOA estimation algorithm, in which the estimated 2-D angles are automatically paired without extra pairing procedure. Particularly, by utilizing the ℓ p (0 < p < 1) norm and majorization–minimization method jointly, the proposed algorithm solves the grid mismatch problem effectively and accordingly enhances the 2-D DOA estimation performance. Finally, numerical simulations demonstrate the effectiveness and superiority of the proposed arrays and 2-D off-grid DOA estimation algorithm. [ABSTRACT FROM AUTHOR]

This study aims to demonstrate the feasibility of metamaterial application in absorption reduction of 5G electromagnetic (EM) energy in the human head tissue. In a general sense, the radio frequency (RF) energy that received by wireless mobile phone from the base station, will emit to surrounding when the devices are in active mode. Since the latest fifth generation technology standard for cellular networks is upon us, the emission of radiation from any wireless devices needs to be taken into consideration. This motivation helps to prepare this paper that focuses on construction of novel and compact square-shaped metamaterial (SM) design to reduce electromagnetic exposure to humans. The commercially available substrate material known as FR-4 with thickness of 1.6 mm was selected to place the metamaterial design on it. The electromagnetic properties and Specific Absorption Rate (SAR) analyses were carried out numerically by utilising high-performance 3D EM analysis, Computer Simulation Technology Studio (CST) software. Meanwhile, for the validation purpose, the metamaterial designs for both unit and array cells were fabricated to measure the electromagnetic properties of the material. From the numerical simulation, the introduced SM design manifested quadruple resonance frequencies in multi bands precisely at 1.246 (at L-band), 3.052, 3.794 (at S-band), and 4.858 (C-band) GHz. However, the comparison of numerically simulated and measured data reveals a slight difference between them where only the second resonance frequency was decreased by 0.009 GHz while other frequencies were increased by 0.002, 0.045, and 0.117 GHz in sequential order. Moreover, the SAR analysis recorded high values at 3.794 GHz with 61.16% and 70.33% for 1 g and 10 g of tissue volumes, respectively. Overall, our results demonstrate strong SAR reduction effects, and the proposed SM design may be considered a promising aspect in the telecommunication field. [ABSTRACT FROM AUTHOR]

Three-dimensional ion and particle concentrations under hydrodynamic focusing in a Y-shaped square microchannel are numerically simulated to clarify the decrease of the ion concentration along the flow direction within the focused particle stream. The simulation model is theoretically governed by the laminar flow and advection–diffusion equations. The governing equations are solved by the finite volume method. The ion and particle concentration distributions at five cross sections after the confluence of the branch channels are analyzed in 30 cases in which the sheath to sample flow rate ratio Qsh/Qsam and the Reynolds number Re are varied as parameters. The results show that the decrease of the cross-sectional average ion concentration along the flow direction within the particle stream c ¯ i is described by the diffusion length during the residence time with a characteristic velocity scale. In addition, the deformation of the particle stream due to inertial effects is described by a scaled Reynolds number that is a function of the flow rate ratio. The simulated particle stream thicknesses are validated by theory and a simple experiment. This paper reveals the relationship between the ion and particle concentrations and the dimensionless parameters for hydrodynamic focusing in the Y-shaped square microchannel under typical conditions. [ABSTRACT FROM AUTHOR]

With the increasing demand for parts with large sizes and complex cross-sectional shapes, the required target shapes are increasingly difficult to meet. In this paper, a flexible 3D stretch bending device has been developed, which can form complex cross-sectional 3D parts with 2 degrees of freedom at one time and can form large sizes 3D parts. Compared with traditional monolithic molds, discrete molds using in flexible 3D stretch bending forming are more convenient for shape adjustment of target profile. The multi-point roller dies are composed of multiple different roller-type die units. In order to better evaluate the forming accuracy of 3D parts, the influence of the number, shape, and surface of the roller dies on the forming results is discussed. The influence of different parameters on the forming accuracy is studied by numerical simulation, and the results are compared with the experimental results. From the perspective of forming accuracy, the influence of FSBR process and different parameters on the forming result is analyzed. Analysis of the dimple and shape errors of the FSBR parts shows that the number, shape, and surface of RDU directly affect the forming accuracy. By modifying the die parameters, the surface dimples can be reduced and the forming accuracy can be improved. [ABSTRACT FROM AUTHOR]

This paper addresses the physical mechanism of intermittent swimming by considering the burst-and-coast regime of fish swimming at different speeds. The burst-and-coast regime consists of a cycle with two successive phases, i.e., a phase of active undulation powered by the fish muscles followed by a passive gliding phase. Observations of real fish whose swimming gait is forced in a water flume from low to high speed regimes are performed, using a full description of the fish kinematics and mechanics. We first show that fish modulate a unique intrinsic cycle to sustain the demanded speed by modifying the bursting to coasting ratio while maintaining the duration of the cycle nearly constant. Secondly, we show using numerical simulations that the chosen kinematics by correspond to optimized gaits for swimming speeds larger than 1 body length per second. Li et al. use experimental observations of red-nose tetrafish and mathematical simulations to model the burst-and-coast swimming regime. This study shows that in order to sustain the necessary speed, fish adopt a unique intrinsic cycle by modifying the burst to coast ratio and can implement this pattern at a range of swimming speeds. [ABSTRACT FROM AUTHOR]

The inner ear, or cochlea, is a fluid-filled organ housing the mechanosensitive hair cells. Sound stimulation is relayed to the hair cells through waves that propagate on the elastic basilar membrane. Sensorineural hearing loss occurs from damage to the hair cells and cannot currently be cured. Although drugs have been proposed to prevent damage or restore functionality to hair cells, a difficulty with such treatments is ensuring adequate drug delivery to the cells. Because the cochlea is encased in the temporal bone, it can only be accessed from its basal end. However, the hair cells that are responsible for detecting speech-frequency sounds reside at the opposite, apical end. In this paper we show that steady streaming can be used to transport drugs along the cochlea. Steady streaming is a nonlinear process that accompanies many fluctuating fluid motions, including the sound-evoked waves in the inner ear. We combine an analytical approximation for the waves in the cochlea with computational fluid dynamic simulations to demonstrate that the combined steady streaming effects of several different frequencies can transport drugs from the base of the cochlea further towards the apex. Our results therefore show that multi-frequency sound stimulation can serve as a non-invasive method to transport drugs efficiently along the cochlea. [ABSTRACT FROM AUTHOR]

In this paper, we investigate a delay reaction–diffusion–advection model with ideal free dispersal. The stability of positive steady-state solutions and the existence of the associated Hopf bifurcation are obtained by analyzing the principal eigenvalue of an elliptic operator. By the normal form theory and the center manifold reduction, the stability and bifurcation direction of Hopf bifurcating periodic solutions are obtained. Moreover, numerical simulations and a brief discussion are presented to illustrate our theoretical results. [ABSTRACT FROM AUTHOR]

Springback compensation is considered as the best method to reduce springback error. In view of the springback defect of 3D deformed workpiece, a springback compensation method based on variable compensation factor is proposed. This method can accelerate the convergence speed of iterative compensation. In this paper, the 3D flexible stretch bending of multi-point roller die technology (3D FSB-MPRD) is introduced firstly, and then, the principle of the springback compensation method based on variable compensation factor is explained. In order to improve the springback compensation accuracy of workpiece, the total springback compensation process is divided into horizontal bending springback compensation and vertical bending springback compensation. Taking the T-shaped profile with variable curvature as the research object, the die surface is optimized and the optimal springback compensation factor is obtained by using numerical simulation after multiple iterations. Finally, the results of springback compensation are compared with the desired shape. And the effectiveness of the springback compensation method based on variable compensation factor is verified by comparing the simulation results with the test results. [ABSTRACT FROM AUTHOR]

This paper is concerned with the pinning synchronization control issue for a class of discrete-time complex dynamical networks. By resorting to the interval observer approach, a novel pinning synchronization control strategy is adopted to control a small fraction of the network nodes with hope to reduce the implementation cost. By using the Lyapunov stability theorem, some synchronization criteria have been derived to ensure the desired synchronization performance. Finally, a numerical simulation is presented to illustrate the effectiveness and usefulness of the theoretical results. [ABSTRACT FROM AUTHOR]

To tackle the problem of the desired signal (DS) steering vector mismatch, especially in the situation of direction-of-arrival error and array perturbations, a robust interference-plus-noise covariance matrix (INCM) reconstruction method based upon DS removal is presented. Unlike previous studies, this paper proposes to remove the DS component from the training data by building a blocking matrix, which is computed as the inverse of the DS-plus-noise covariance matrix (DSNCM). More specifically, to increase the robustness against arbitrary mismatches, the DS steering vector estimated as the prime eigenvector of the DS matrix, which is attained through integrating the Capon spectrum estimator over the annulus uncertainty sets of the mainlobe region in advance, is adopted to give a faithful blocking matrix. After that, utilizing the obtained blocking matrix to process the training data, the quasi INCM is computed indeed. Finally, a precise INCM is reconstructed by projecting the principal components of the quasi INCM onto the aforesaid DSNCM. Numerical simulations have illustrated that the proposed adaptive beamformer can outperform the existing ones and gain almost optimal performance under different scenarios. [ABSTRACT FROM AUTHOR]

This paper presents the results of experimental and computational studies of instability development and mixing at the contact boundaries between gases of different densities. It has been shown that instability and mixing at two contact boundaries in a three-layer gas systems occur after a shock wave with a Mach number M = 1.3 that forms on the left end and moves along the tube has passed through the contact boundaries. Two experiments were performed, in the first of which the central layer was filled with a heavy gas (SF6 gas), and in the second experiment, it was filled with a light gas (helium). On the left and right of the central layer was air at atmospheric pressure. A comparison of the results was performed. [ABSTRACT FROM AUTHOR]

This paper provides the first systematic epistemological account of simulated data in empirical science. We focus on the epistemic issues modelers face when they generate simulated data to solve problems with empirical datasets, research tools, or experiments. We argue that for simulated data to count as epistemically reliable, a simulation model does not have to mimic its target. Instead, some models take empirical data as a target, and simulated data may successfully mimic such a target even if the model does not. We show how to distinguish between simulated and empirical data, and we also offer a definition of simulation that can accommodate Monte Carlo models. We shed light on the epistemology of simulated data by providing a taxonomy of four different mimicking relations that differ concerning the nature of the relation or relata. We illustrate mimicking relations with examples from different sciences. Our main claim is that the epistemic evaluation of simulated data should start with recognizing the diversity of mimicking relations rather than presuming that only one relation existed. [ABSTRACT FROM AUTHOR]

In this paper, we study a novel deterministic and stochastic SIR epidemic model with vertical transmission and media coverage. For the deterministic model, we give the basic reproduction number R 0 which determines the extinction or prevalence of the disease. In addition, for the stochastic model, we prove existence and uniqueness of the positive solution, and extinction and persistence in mean. Furthermore, we give numerical simulations to verify our results. [ABSTRACT FROM AUTHOR]

A new numerical approach for the time-dependent wave and heat equations as well as for the time-independent Poisson equation developed in Part 1 is applied to the simulation of 1-D and 2-D test problems on regular and irregular domains. Trivial conforming and non-conforming Cartesian meshes with 3-point stencils in the 1-D case and 9-point stencils in the 2-D case are used in calculations. The numerical solutions of the 1-D wave equation as well as the 2-D wave and heat equations for a simple rectangular plate show that the accuracy of the new approach on non-conforming meshes is practically the same as that on conforming meshes for both the Dirichlet and Neumann boundary conditions. Moreover, very small distances ( 0.1 h - 10 - 9 h where h is the grid size) between the grid points of a Cartesian mesh and the boundary do not decrease the accuracy of the new technique. The application of the new approach to the 2-D problems on an irregular domain shows that the order of accuracy is close to four for the wave and heat equations and is close to five for the Poisson equation. This is in agreement with the theoretical results of Part 1 of the paper. The comparison of the numerical results obtained by the new approach and by FEM shows that at similar 9-point stencils, the accuracy of the new approach on irregular domains is two orders higher for the wave and heat equations and three orders higher for the Poisson equation than that for the linear finite elements. Moreover, the new approach yields even much more accurate results than the quadratic and cubic finite elements with much wider stencils. An example of a problem with a complex irregular domain that requires a prohibitively large computation time with the finite elements but can be easily solved with the new approach is presented. [ABSTRACT FROM AUTHOR]

Efficient cuttings transport and improving rate of penetration (ROP) are two major challenges in horizontal drilling and extended reach drilling. A type of jet mill bit (JMB) may provide an opportunity to catch the two birds with one stone: not only enhancing cuttings transport efficiency but also improving ROP by depressuring at the bottom hole. In this paper, the JMB is further improved and a new type of depressure-dominated JMB is presented; meanwhile, the depressurization capacity of the depressure-dominated JMB is investigated by numerical simulation and experiment. The numerical study shows that low flow-rate ratio helps to enhance the depressurization capacity of the depressure-dominated JMB; for both depressurization and bottom hole cleaning concern, the flow-rate ratio is suggested to be set at approximately 1:1. With all other parameter values being constant, lower dimensionless nozzle-to-throat-area ratio may result in higher depressurization capacity and better bottom hole cleaning, and the optimal dimensionless nozzle-to-throat-area ratio is at approximately 0.15. Experiments also indicate that reducing the dimensionless flow-rate ratio may help to increase the depressurization capacity of the depressure-dominated JMB. This work provides drilling engineers with a promising tool to improve ROP. [ABSTRACT FROM AUTHOR]

In this paper, we study the reasonability of linearized approximation and Hopf bifurcation control for a fractional-order delay Bhalekar–Gejji (BG) chaotic system. Since the current study on Hopf bifurcation for fractional-order delay systems is carried out on the basis of analyses for stability of equilibrium of its linearized approximation system, it is necessary to verify the reasonability of linearized approximation. Through Laplace transformation, we first illustrate the equivalence of stability of equilibrium for a fractional-order delay Bhalekar–Gejji chaotic system and its linearized approximation system under an appropriate prior assumption. This semianalytically verifies the reasonability of linearized approximation from the viewpoint of stability. Then we theoretically explore the relationship between the time delay and Hopf bifurcation of such a system. By introducing the delayed feedback controller into the proposed system, the influence of the feedback gain changes on Hopf bifurcation is also investigated. The obtained results indicate that the stability domain can be effectively controlled by the proposed delayed feedback controller. Moreover, numerical simulations are made to verify the validity of the theoretical results. [ABSTRACT FROM AUTHOR]

Quantum catalysis is a feasible approach to increase the performance of continuous-variable quantum key distribution (CVQKD), involving the special zero-photon catalysis (ZPC) operation. However, in the practical point of view, the improvement effect of this operation will be limited by the imperfection of the photon detector. In this paper, we show that the ZPC operation at the sender can be simulated by a post-selection method without implementing it in practical devices. While performing this virtual version of ZPC in CVQKD, we can not only reach the ideal case of its practical implementation with minimal hardware requirement, but also keep the benefit of Gaussian security proofs. Based on Gaussian modulated coherent state protocols with achievable parameters, we enhance the security of the proposed scheme from the asymptotical case to the finite-size scenario and composable framework. Simulation results show that similar to the asymptotical case, both the maximal transmission distance and the tolerable excess noise of virtual ZPC-involved CVQKD outperform the original scheme and the scheme using virtual photon subtraction while considering finite-size effect and composable security. In addition, the virtual ZPC-involved CVQKD can tolerate a higher imperfection of the detector, enabling its practical implementation of the CVQKD system with state-of-the-art technology. [ABSTRACT FROM AUTHOR]

In this paper, we study asymptotic properties of nonlinear support vector machines (SVM) in high-dimension, low-sample-size settings. We propose a bias-corrected SVM (BC-SVM) which is robust against imbalanced data in a general framework. In particular, we investigate asymptotic properties of the BC-SVM having the Gaussian kernel and compare them with the ones having the linear kernel. We show that the performance of the BC-SVM is influenced by the scale parameter involved in the Gaussian kernel. We discuss a choice of the scale parameter yielding a high performance and examine the validity of the choice by numerical simulations and actual data analyses. [ABSTRACT FROM AUTHOR]

In the shipbuilding industry, the traditional manufacturing method for the complicated ship hull metal plates is line heating method, which is not only labor intensive but also inefficient. Considerable efforts have been taken to develop the new automated manufacturing processes at a reasonable quality, efficiency and price during the last few decades. This paper presents a novel flexible forming process called incremental bending to achieve complicated plates. In this method, the initial metal plate is supported by some rotatable hydraulic cylinders and the punches move according to the given path, which is decided by minimum energy method and springback compensation method, to achieve the final plate. Taking one variable curved metal plate as one example, this paper investigates the formability of this novel process based on experiment and numerical simulation. During the numerical simulation, the implicit method is used and the gravity of the plate is considered mainly for the automatic positioning of the plate during each springback process. Results show that the incremental bending process can achieve variable curved metal plates with good accuracy, high efficiency, and relatively small punch load. In comparison with the existing methods, the new process has greater potentiality in the ship hull manufacturing industry. [ABSTRACT FROM AUTHOR]

This paper proposes a new fault tolerant control strategy for a five-phase permanent magnet synchronous motor (PMSM) drive under single-phase open circuit condition. The loss of one phase causes problems such as disturbing rotating magneto-motive force (MMF) and generating undesirable torque pulsations. The development of suitable control strategy is a required task in order to ensure disturbance-free operation during post-fault operation. This paper proposes a new control technique for a five-phase PMSM based on adaptive sliding mode control (ASMC) in post-fault under the loss of one stator phase. The proposed method is compared to fault tolerant control strategy based on proportional resonant (PR) controller. The two control strategies are different from theoretical viewpoint proving their abilities to overcome the fault situation with favorable dynamic performance and faster control response of ASMC compared with PR controller. Depicted set of numerical simulation results always shows a close conformity with the developed theoretical background. [ABSTRACT FROM AUTHOR]

This paper contains a discussion of striking similarities between influential philosophical concepts of the past and the approaches currently employed in selected areas of computer science. In particular, works of the Pythagoreans, Plato, Abelard, Ash’arites, Malebranche and Berkeley are presented and contrasted with such computer science ideas as digital computers, object-oriented programming, the modelling of an object’s actions and causality in virtual environments, and 3D graphics rendering. The intention of this paper is to provoke the computer science community to go off the beaten path in order to find inspiration for the development of new approaches in software engineering. [ABSTRACT FROM AUTHOR]

In this paper, we discuss about multiple coordinated robots that can form a fixtureless manufacturing cell. It is very important to ensure that the system stiffness is sufficient for manufacturing operations when external forces are exerted on the system. For this reason, a method is developed to model and analyze the stiffness of a multiple coordinated robot system. In this paper, first, the stiffness of a multiple coordinated robot system is defined. Similar to a single-arm robot, this definition provides us with a criterion to evaluate the stiffness performance of the entire multiple robot system. Second, a static stiffness model is derived including joint stiffness and link stiffness, and then this model is extended to a multiple robot system. Third, the coordinated static stiffness model is validated, and a comparison is made through simulation between a dual robot system and a single robot system. Finally, the developed model is applied to a real coordinated dual-arm robot system for validation. [ABSTRACT FROM AUTHOR]

The paper discusses the problems of forming parts such as stepped shafts by cross wedge rolling (CWR). In industrial practice, this rolling process is performed at stages, i.e., in several passes, when large cross-sectional reductions are involved. The same can also be done using a different design of this forming process, namely, multi-wedge cross rolling (MWCR), in which the workpiece is simultaneously formed by several pairs of tools (wedges). This paper compares the above two methods with respect to forming a drive shaft. Wedge tools used in both forming processes are described, and the numerical results of the simulations performed to verify the adopted solutions are reported. The results demonstrate that theMWCR method offers more advantages than the classical CWR technique. Consequently, MWCR is then verified in experimental tests. The experimental results confirm that parts such as stepped shafts can be formed by the MWCR method. [ABSTRACT FROM AUTHOR]

Researching on the relationships among different multiple weighted type fractional Fourier transform (multi-WFRFT) schemes, we in this paper provide the modulation order relation of different multi-WFRFT in theory. Moreover, we also prove that the two matrix spaces (i.e., 4-WFRFT and multi-WFRFT) are equivalent. To apply multi-WFRFT into the wireless communication, we design the implementation structure of multi-WFRFT (in particular, for 2n-WFRFT scheme). Furthermore, the generalized hybrid carrier modulation (GHCM) system has been proposed in this paper, which can be degenerated to the classical hybrid carrier modulation (HCM) system with special parameters. We also verify the modulation order relationship between multi-WFRFT by numerical simulations. Leveraging the theory and structure of multi-WFRFT, we finally discuss its potential applications over secure communication and multiple input multiple output (MIMO) system. [ABSTRACT FROM AUTHOR]

This paper presents a novel tool positioning method for flank milling with a barrel cutter. It can be used to compute the tool position, at which the cutter can contact with the surface at two points. The strip width of the tool position is larger than that of the tool position solved by the single-point offset method. An error distribution curve was used to describe the gap between a barrel cutter and a surface. This paper presented the existence of the tool position with double contact points through analyzing different types of error distribution curves. The cutter was lifted from the surface firstly, and then, the tool orientation was adjusted by changing the tilt angle and the yaw angle. The method presented was applied on a rule surface, a sculptured surface, and a pressure surface of a blade. The tool positions were analyzed to demonstrate the validity of our method. The computation and simulation results indicate that the double-point contact tool position can be solved by our method. [ABSTRACT FROM AUTHOR]

This paper describes a method for determining the strain state of a thin anisotropic plate with elastic arbitrarily arranged elliptical inclusions. Complex potentials are used to reduce the problem to determining functions of generalized complex variables, which, in turn, comes down to an overdetermined system of linear algebraic equations, solved by singular expansions. This paper presents the results of numerical calculations that helped establish the influence of rigidity of elastic inclusions, distances between inclusions, and their geometric characteristics on the bending moments occurring in the plate. It is found that the specific properties of distribution of moments near the apexes of linear elastic inclusions, characterized by moment intensity coefficients, occur only in the case of sufficiently rigid and elastic inclusions. [ABSTRACT FROM AUTHOR]

In this paper, we give a complete analysis of the equilibrium points of background neural networks with uniform firing rates. By using continuity, monotonicity of some functions and Rolle's theorem, the number of equilibrium points and their locations are obtained. Moreover, some novel sufficient conditions are given to guarantee the stability of the equilibrium points for the network model by utilizing Taylor's theorem. A simulation example is conducted to illustrate the theories developed in this paper. [ABSTRACT FROM AUTHOR]

Frequency scanning is a method of obtaining the frequency response of a system by injecting a small-amplitude wide-band signal as an input in a time domain simulation of the system. This is an alternative to analytical derivation of small-signal models, especially for complex grid-connected power electronic systems (PESs). These models are required for the study of adverse interaction of PES with lightly damped oscillatory modes in a power system. The use of the frequency scans for conventional small-signal stability analysis is predicated upon the time-invariance of the underlying model. Since PES are generally time-periodic, time-invariance may be achieved in some transformed variables. Although the DQ transformation is suitable in many situations, it is not so for systems with low-order harmonics, individual-phase schemes, unbalanced or single-phase systems, and PES with negative-sequence controllers. This paper proposes the use of dynamic phasor variables in such situations since the underlying model in these variables is time-invariant. The procedure for dynamic phasor based scanning is, however, intricate because wide-band signal injection results in the simultaneous presence of harmonic dynamic phasor components. The paper outlines this procedure and presents illustrative case studies of Thyristor Controlled Series Compensator (TCSC) and STATCOM. For the TCSC, a comparison of the frequency response obtained from the scanning method and the one obtained from an approximate analytical dynamic phasor model is also presented . [ABSTRACT FROM AUTHOR]

In order to resolve the co-channel inter-cell interference problem in heterogeneous networks (HetNet), the feature of almost blank subframes (ABS) in the time domain of the enhanced inter-cell interference coordination (eICIC) is utilized. In this paper, an ABS configuration design is developed on downlink in HetNet and the associated resource allocation problem for maximizing the system performance with fairness among user equipments (UEs) is considered. Compared to conventional problems, the resource assignment problems include the configuration of ABS pattern and the resource allocation for macro UEs and pico UEs, which aims to maximize the downlink throughput and balance the traffic offloading in intra-frequency HetNet deployments. First, this paper introduces an ABS pattern design by using the channel condition, which is developed in terms of the time domain resource. Subframes are categorized as protected or normal subframes for reducing interference impact to pico UEs. Based on the configuration of the ABS pattern, we develop a grouping strategy to determine which pico UEs use either protected or normal subframes. Besides, the assignment of resource blocks with respect to the resource in the frequency domain is developed along with the fairness among UEs. The proposed joint allocation scheme takes the system throughput and the fairness into account, and has better performance than the existing schemes. Simulation results also reveal that the performance of the proposed joint allocation scheme approximates the optimal solution with the full search scheme. [ABSTRACT FROM AUTHOR]

This article develops estimators for certain population characteristics using a judgment post stratified (JPS) sample. The paper first constructs a conditional JPS sample with a reduced set size K by conditioning on the ranks of the measured observations of the original JPS sample of set size $$H \ge K$$ . The paper shows that the estimators of the population mean, median and distribution function based on this conditional JPS sample are consistent and have limiting normal distributions. It is shown that the proposed estimators, unlike the ratio and regression estimators, where they require a strong linearity assumption, only need a monotonic relationship between the response and auxiliary variable. For moderate sample sizes, the paper provides a bootstrap distribution to draw statistical inference. A small-scale simulation study shows that the proposed estimators based on a reduced set JPS sample perform better than the corresponding estimators based on a regular JPS sample. [ABSTRACT FROM AUTHOR]

The boundedness of chaotic systems plays an important role in investigating the stability of the equilibrium, estimating the Lyapunov dimension of attractors, the Hausdorff dimension of attractors, the existence of periodic solutions, chaos control, and chaos synchronization. However, as far as the authors know, there are only a few papers dealing with bounds of high-order chaotic systems due to their complex algebraic structure. To sort this out, in this paper, we study the bounds of a high-order Lorenz-Stenflo system arising in mathematical physics. Based on Lyapunov stability theory, we show that there exists a globally exponential attractive set for this system. The innovation of the paper is that we not only prove that this system is globally bounded for all the parameters, but also give a family of mathematical expressions of global exponential attractive sets of this system with respect to its parameters. We also study some other dynamical characteristics of this chaotic system such as invariant sets and chaotic behaviors. To justify the theoretical analysis, we carry out detailed numerical simulations. [ABSTRACT FROM AUTHOR]

The present paper deals with free vibration analysis of laminated composite skew plates with and without cut-outs. The experimental investigation along with numerical simulation has been presented in this paper for complete understanding of the dynamic behaviour of laminated skew plates with cut-out. Glass fibre-reinforced laminated composite plates have been prepared by resin infusion process using vacuum bagging technique in the laboratory for experimental analysis. The experimental studies have been carried out on skew composite plates with varying size of cut-out placed at the centre. The numerical analysis has been carried out by developing a computer code in MATLAB. Special attention is drawn on the formulation of mass matrix by considering effect of rotary inertia. The results obtained by the finite element formulation using nine-noded isoparametric plate-bending elements are validated by comparing the results from relevant published literature. The numerical and experimental data are then compared for experimental verification of present investigation. The consistency of mode shapes between experimental and numerical investigations is checked by using modal assurance criteria. [ABSTRACT FROM AUTHOR]

A nine-level hybrid symmetric cascaded multilevel converter (MLC) fed induction motor drive is proposed in this paper. The proposed converter is capable of producing nine output voltage levels by using the same number of power cells as that of conventional five-level symmetric cascaded H-bridge converter. Each phase in this configuration consists of one five-level transistor-clamped H-Bridge (TCHB) power cell and one three-level H-bridge power cell with equal dc link voltages, and they are connected in cascade. Due to cascade connection and equal dc link voltage, the power shared by each power cell is nearly equal. Near-equal power sharing enables the feature of improving input current quality by using an appropriate phase-shifting multi-winding transformer at the converter input. In this paper, the operation of the converter is explained using staircase and hybrid multi-carrier sine PWM techniques. Further, a detailed analysis for the variations in the dc link capacitor voltages and the dc link mid-point voltage in TCHB power cell is carried out, and the analytical expressions thus obtained are presented. The performance of proposed system is analysed by simulating a 500 hp induction motor drive system in MATLAB/Simulink environment. A laboratory prototype is also developed to validate the claims experimentally. [ABSTRACT FROM AUTHOR]

Shrinking of technology node in advanced VLSI devices and scaling of supply voltage degrade the performance characteristics and reduce the soft error resilience of modern downscaled digital circuits. In this paper, we propose a reliable near-threshold 7T SRAM cell with single ended read and differential write operations based on a previous proposed 5T cell. Our new cell improves read speed without degrading of write speed compared to the recently reported 7T cell. Furthermore, our proposed cell provides high soft error reliability amongst all the SRAM cells mentioned in this paper. We compared the performance and reliability characteristics of 5T, 6T, 8T and previous 7T cells with our new 7T SRAM cell to show its efficacy. The simulations are performed using HSPICE in 20 nm FinFET technology at V = 0.5 V. The results show that the new 7T cell has high write speed, read and write margins with improved read speed and low leakage power in the hold '0' state compared to 5T cell. In addition, the study of performance parameters under process and environmental variations considering ageing effect in near-threshold region shows the robustness of the proposed 7T SRAM cell against these variations. [ABSTRACT FROM AUTHOR]

Large and thick-walled aluminium forgings exhibit shape distortions induced by residual stresses. To restore the nominal geometry, a series of highly manual and time-consuming reshaping operations need to be carried out. In this paper, we are concerned with the development of efficient computer simulation tools to assist operators in bending straightening, which is one of the most common reshaping operations. Our approach is based on the computation of reshaping diagrams, a tool that allows selecting a nearly optimal bending load to be applied in order to minimize distortion. Most importantly, we show that the reshaping diagram needs not to account for the residual stress field, as its only effect is to shift of the reshaping diagram by some offset. That is, the overall behaviour including a realistic 3D residual stress field in a forged part can be retrieved by shifting the residual stress free reshaping diagram by the appropriate offset. Finally, we propose a strategy in order to identify the offset on-the-fly during the reshaping operation using simple force-displacement measures. [ABSTRACT FROM AUTHOR]

In this paper, we study the dynamics property of a stochastic HIV model with Beddington–DeAngelis functional response. It has a unique uninfected steady state. We prove that the model has a unique global positive solution. Furthermore, if the basic reproductive number is not larger than 1, the asymptotic behavior of the solution is stochastically stable. Otherwise, it fluctuates randomly around the infected steady state of the corresponding deterministic HIV model. Finally, some numerical simulations are carried out to verify our results. [ABSTRACT FROM AUTHOR]

Differential game model of limited resource extraction with dynamic updating is studied in the paper. The class of games with dynamic updating is new in the theory of differential games. Cooperative setting of limited resource extraction with dynamic updating is considered. Optimal strategies, cooperative payoff, characteristic function and allocation rule for cooperative payoff between the players are derived in an explicit form. As an optimality principle or cooperative solution Shapley value is used. Results of numerical simulation in the Python environment are demonstrated. [ABSTRACT FROM AUTHOR]

In this paper, we construct a tritrophic level food chain model considering the model parameters as fuzzy interval numbers. We check the positivity and boundedness of solutions of the model system and find out all the equilibrium points of the model system along with its existence criteria. We perform stability analysis at all equilibrium points of the model system and discuss in the imprecise environment. We also perform meticulous numerical simulations to study the dynamical behavior of the model system in detail. Finally, we incorporate different harvesting scenarios in the model system and deploy maximum sustainable yield (MSY) policies to determine optimum level of harvesting in the imprecise environment without putting any unnecessary extra risk on the species toward its possible extinction. [ABSTRACT FROM AUTHOR]

This paper discusses the behavior and contributing factors of land subsidence in the intersection area of Expressway (Expwy) 78 and Taiwan High Speed Rail (THSR), located on Choshui River alluvial fan-delta (CRAFD) to the midwest of Taiwan. Since the CRAFD has been suffering a long-time problem of land subsidence, the transportation safety of THSR and Expwy 78 thus has become a major concern. The subsidence of CRAFD can be attributed to several factors, including overexploitation of groundwaters for area development. However, additional loadings of Expwy 78 and THSR structures would appear to deteriorate the problem. It would be of interest to know the influence of various factors on subsidence of the study area where the subsidence has now become most serious along the entire THSR route. It would also be advisable to provide information on the potential effects of subsidence on the integrity of THSR structure. With these aims, we perform analyses on the subsidence of the area based on 8-year on-site monitoring and numerical simulations. Results indicate, in a period started approximately from Expwy 78 construction, the average subsiding rate would be 10.53 cm/year, with relative contributions of 14.1%, 55.2%, 11.8%, 11.6%, and 7.3%, respectively, by the factors of soil creeping, previous overpumping, groundwater fluctuations, and loadings of Expwy 78 and THSR. We also estimate 23% and 77% of total subsidence occurred as the compressions of soils within and beyond the installation depth of THSR piles, which might impair pile bearing capacity and vertical alignment, respectively, of THSR. [ABSTRACT FROM AUTHOR]

In this paper, an improved fractional-order model of boundary formation in the Drosophila large intestine dependent on Delta-Notch pathway is proposed for the first time. The uniqueness, nonnegativity, and boundedness of solutions are studied. In a two cells model, there are two equilibriums (no-expression of Delta and normal expression of Delta). Local asymptotic stability is proved for both cases. Stability analysis shows that the orders of the fractional-order differential equation model can significantly affect the equilibriums in the two cells model. Numerical simulations are presented to illustrate the conclusions. Next, the sensitivity of model parameters is calculated, and the calculation results show that different parameters have different sensitivities. The most and least sensitive parameters in the two cells model and the 60 cells model are verified by numerical simulations. What is more, we compare the fractional-order model with the integer-order model by simulations, and the results show that the orders can significantly affect the dynamic and the phenotypes. [ABSTRACT FROM AUTHOR]

In this paper, we propose and study a stochastic two-species cooperation model with functional response in a polluted environment. We first perform the survival analysis and establish sufficient conditions for extinction, weak persistence, and stochastic permanence. Then we further perform the survival analysis based on the temporal average of population size and derive sufficient conditions for the strong persistence in the mean and weak persistence in the mean. Finally, we present numerical simulations to justify the theoretical results. [ABSTRACT FROM AUTHOR]