Search

In the presented research article, the intelligence based numerical computation of artificial neural network backpropagated with Levenberg-Marquardt algorithm has been developed to analyze the novel ferrofluid flow model in the presence of magnetic dipole. Heat transfer effects are also incorporated along the horizontal. The designed fluid flow model initially represented by system of partial differential equations are converted into system of non-linear ordinary differential equations through suitable similarity transformations. The reference dataset of the possible outcomes is obtained from Adam numerical solver for the different scenarios of flow model by variation of co-efficient of the thermal expansion, Eckert number, suction parameter, magnetization and radiation parameter. The approximated solutions are interpreted for designed model by testing, training and validation process of backpropagated neural networks. Furthermore, the comparative studies and performance analysis of used algorithm is validated through regression analysis, histogram studies, correlation index and results of mean square error.

Copyright of Journal of Dalian Ocean University is the property of Journal of Dalian Ocean University Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

For efficiency improvement and state monitoring of the propeller of a ship, a non-smooth surface is a conventional approach to reducing drag, saving energy, and providing a stabler sensing condition. In this paper, we studied the effects of the surface roughness and protrusions on propeller performance, and the hydrodynamic performance of a marine propeller, including the propeller thrust, torque, and open water efficiency, was analyzed for different surface conditions. By ANSYS meshing, the Y+ value of the rotating propeller was ensured to be less than 5. The shear stress transport (SST) turbulence model, stationary domain, and rotating domain were adopted to model the water flow during simulation in an ANSYS software CFX module. In our numerical calculations, there were four surface conditions for the rotating blade of the propeller: a non-slip smooth surface, a surface with a roughness of 5 μm, and surfaces with protrusions of 0.2 and 0.3 mm. The results show that the efficiency of the propeller is increased by protrusions located on the pressure surface. The propeller with 0.2 mm protrusions shows the best performance. Compared with the non-slip smooth wall condition, the thrust force is increased, and the increase in propeller efficiency is 2.83% when the advance coefficient of the propeller J is 0.9 and 6.40% when J is 1.0. The propeller efficiency is reduced by blade surface roughness, but the flow field is more stationary for the propeller with surface protrusions, which is beneficial for propeller shaft sensors. The other hydrodynamic parameters are also analyzed to illustrate their effect on the propeller performance. [ABSTRACT FROM AUTHOR]

This fundamental research was conducted to predict the grain size of austenitic stainless-steel after plasma cutting process using experiment and non-linear probabilistic numerical computation with self-developed algorithm which was written and compiled using Fortran-based subroutines and utility routines available in commercial FEM software. For grain modelling, the non-linear numerical programming codes consisted of fourth-order Runge–Kutta method for solving ordinary differential equation of grain growth formula with major parameters such as initial grain size, activation energy, and kinetic constant which were measured by using dilatometer on specimen samples at various temperatures and holding times. In order to replicate the actual thermal cutting process, customized conical heat source model was developed and employed. The probabilistic approach in numerical computation was executed using Monte Carlo method by setting major process parameter of input power based on normal distribution with defined mean and standard deviation which were randomized following linear congruential generator and Box-Muller algorithm. This comprehensive numerical computation based on deterministic and probabilistic FEM was established using nonlinear thermomechanical method with hexahedral element type including finer mesh on cutting section and coarser at base plate. For verification purpose, a series of experiments using fully automated system was carried out on SS316L plate with 4-mm thickness. From the analysis of results, acceptable discrepancy was achieved in grain size prediction obtained between numerical methods and experiment with the error percentage of up to 9.2% and 14.5% for probabilistic and deterministic analyses respectively. [ABSTRACT FROM AUTHOR]

This paper studies the localization problem using noisy range-difference measurements, or equivalently time difference of arrival (TDOA) measurements. There is a reference sensor, and for each other sensor, the TDOA measurement is obtained with respect to the reference one. By minimizing the sum of squared errors, a nonconvex constrained least squares (CLS) problem is formulated. In this work, we focus on devising an algorithm to seek the global minimizer of the CLS problem, hoping that the numerical solution meets some precision requirement in terms of relative error. Based on the Lagrange multiplier method, we first branch the feasible Lagrange multiplier set into several subsets and develop a workflow in terms of if-then-else control structure to seek the global minimizer by searching for the optimal Lagrange multiplier. The execution order is carefully organized so that it is in line with the general principle of putting the flow that one normally understands to be executed first. We then dive into detailed searching methods in different cases and conduct computational error analysis, giving the error bound on the Lagrange multiplier, when we search for it, to meet the precision requirement on an approximate solution. Based on the above achievements, a programmable global minimizer seeking algorithm is proposed for the CLS problem. Simulations and experimental tests on a public dataset demonstrate the effectiveness of the proposed algorithm. [ABSTRACT FROM AUTHOR]

The aim of this study is to develop a physical model and investigate the bactericidal effect of an automated hand-washing system through numerical computation, which is essential in areas affected by COVID-19 to ensure safety and limit the spread of the pandemic. The computational fluid dynamics approach is used to study the movement of the solution inside the hand-washing chamber. The finite element method with the k-ε model is applied to solve the incompressible Navier–Stokes equations. The numerical results provide insights into the solution’s hydrodynamic values, streamlines, and density in the two cases of with a hand and without a hand. The pressure and mean velocity of the fluid in the hand-washing chamber increases when the inlet flow rates increase. When the hand-washing chamber operates, it creates whirlpools around the hands, which remove bacteria. In addition, the liquid inlet flow affects the pressure in the hand-washing chamber. The ability to predict the hydraulic and cleaning performance efficiencies of the hand-washing chamber is crucial for evaluating its operability and improving its design in the future.

The numerical solution of the classical Sommerfeld problem is thoroughly discussed in this work. In particular, the computation of the vertical electric field excited by a vertical electric dipole (VED) is taken as a paradigm to discuss some different approaches that have been proposed in the literature (with some new variations included). A detailed study is carried out on the pros and cons of each method as well as their range of numerical efficiency in terms of frequency, ground losses, height of the dipole, and distance to the observation point. We finally propose a numerical implementation of the steepest descent method as a good overall method in terms of accuracy, computational efficiency, and extended range of validity. Asymptotic closed-form expressions for the far-field region are also provided. [ABSTRACT FROM AUTHOR]

Numerical computation of the ruin probability is discussed. The probability is governed by the Volterra type integral equation with infinite domain of integration. Transforming the infinite interval into a bounded interval, we apply the Chebyshev-Gauss-Radau collocation method to obtain numerical solutions. Aymptotic behavior is also numerically implemented. Numerical experiments of test problems show that our scheme works well. [ABSTRACT FROM AUTHOR]

Abstract In this paper, numerical computations are carried out to investigate the seismo-electromagnetic signals arising from the motional induction effect due to an earthquake source embedded in 3-D multi-layered media. First, our numerical computation approach that combines discrete wavenumber method, peak-trough averaging method, and point source stacking method is introduced in detail. The peak-trough averaging method helps overcome the slow convergence problem, which occurs when the source–receiver depth difference is small, allowing us to consider any focus depth. The point source stacking method is used to deal with a finite fault. Later, an excellent agreement between our method and the curvilinear grid finite-difference method for the seismic wave solutions is found, which to a certain degree verifies the validity of our method. Thereafter, numerical computation results of an air–solid two-layer model show that both a receiver below and another one above the ground surface will record electromagnetic (EM) signals showing up at the same time as seismic waves, that is, the so-called coseismic EM signals. These results suggest that the in-air coseismic magnetic signals reported previously, which were recorded by induction coils hung on trees, can be explained by the motional induction effect or maybe other seismo-electromagnetic coupling mechanisms. Further investigations of wave-field snapshots and theoretical analysis suggest that the seismic-to-EM conversion caused by the motional induction effect will give birth to evanescent EM waves when seismic waves arrive at an interface with an incident angle greater than the critical angle θ c = arcsin(V sei/V em), where V sei and V em are seismic wave velocity and EM wave velocity, respectively. The computed EM signals in air are found to have an excellent agreement with the theoretically predicted amplitude decay characteristic for a single frequency and single wavenumber. The evanescent EM waves originating from a subsurface interface of conductivity contrast will contribute to the coseismic EM signals. Thus, the conductivity at depth will affect the coseismic EM signals recorded nearby the ground surface. Finally, a fault rupture spreading to the ground surface, an unexamined case in previous numerical computations of seismo-electromagnetic signals, is considered. The computation results once again indicate the motional induction effect can contribute to the coseismic EM signals.

This paper considers the problem associated with the numerical simulation of the interaction between the cocurrent stream occurring near a monoblock moving in the gas medium and solid fuel combustion products flowing from a solid fuel rocket engine (SFRE). The peculiarity of the approach used is the description of gas-dynamic processes inside the combustion chamber, in the nozzle block, and the down jet based on a single calculation methodology. In the formulated numerical methodology, the calculation of gas-dynamic parameters is based on the solution of unsteady Navier–Stokes equations and the application of a hybrid computational grid. A hybrid block-structured computational grid makes it possible to calculate gas flow near bodies of complex geometric shapes. The simulation of the main phase of interaction, corresponding to the stationary mode of rocket flight in the Earth's atmosphere, has been carried out. A conjugated simulation of the internal ballistics of SFRE and interaction of combustion products jets is conducted. [ABSTRACT FROM AUTHOR]

In this paper, we propose a novel methodology of numerical approximation to analyze flow of a nonlinear embedded hybrid system. For proving that all trajectories of a hybrid system do not enter an unsafe region, many classic numerical approaches such as Euler, Runge–Kutta methods for ordinary differential equations (ODEs) are applied, whereas, there exist several defects, including so-called spurious solutions and ghost fixed points. Moreover, to approximate the proper solution as much as possible, step size selection becomes especially important. In comparison, integrating group preserving scheme (GPS) which calculates true circumstance getting rid of spurious solutions and ghost fixed points, with neural network model which reduces numerical errors, deep GPS (DGPS) eliminates aforementioned adverse factors and gains better numerical approximation using a large time step size. The experimental results show that the proposed method makes safety verification for an embedded hybrid system well. [ABSTRACT FROM AUTHOR]

The Operator axioms have produced new real numbers with new operators. New operators naturally produce new equations and thus extend the traditional mathematical models which are selected to describe various scientific rules. So new operators help to describe complex scientific rules which are difficult described by traditional equations and have an enormous application potential. As to the equations including new operators, engineering computation often need the approximate solutions reflecting an intuitive order relation and equivalence relation. However, the order relation and equivalence relation of real numbers are not as intuitive as those of base-b expansions. Thus, this paper introduces numerical computations to approximate all real numbers with base-b expansions.

We construct a mean-field variational model to study how the dependence of dielectric coefficient (i.e., relative permittivity) on local ionic concentrations affects the electrostatic interaction in an ionic solution near a charged surface. The electrostatic free-energy functional of ionic concentrations, which is the key object in our model, consists mainly of the electrostatic potential energy and the ionic ideal-gas entropy. The electrostatic potential is determined by Poisson's equation in which the dielectric coefficient depends on the sum of concentrations of individual ionic species. This dependence is assumed to be qualitatively the same as that on the salt concentration for which experimental data are available and analytical forms can be obtained by the data fitting. We derive the first and second variations of the free-energy functional, obtain the generalized Boltzmann distributions, and show that the free-energy functional is in general nonconvex. To validate our mathematical analysis, we numerically minimize our electrostatic free-energy functional for a radially symmetric charged system. Our extensive computations reveal several features that are significantly different from a system modeled with a dielectric coefficient independent of ionic concentration. These include the non-monotonicity of ionic concentrations, the ionic depletion near a charged surface that has been previously predicted by a one-dimensional model, and the enhancement of such depletion due to the increase of surface charges or bulk ionic concentrations.

This fundamental research aims to analyse the effect of heat transfer coefficients, plasticity model of evolved material properties and simplified meshing strategy on substrate deformation induced by wire arc additive manufacturing (WAAM) process with dissimilar materials based on experiment and numerical simulation. Throughout the experiment, stainless steel wire SS316L was used as feedstock to build a five-layer and three-string component on an 8-mm-thick low carbon steel S235 as substrate plate by means of a robotic GMAW system with pure argon as shielding gas and diagonal clamping. In order to define heat transfer coefficients by adjusting simulation to experimental results, the transient thermal distribution was to be measured at specific points located in the component layer using Type K thermocouple inserted during the process and on the substrate implanted beforehand. For modelling and simulation, a non-linear thermo-mechanical method was applied in which the component was modelled using rectangular element shape with optimized hexagonal mesh size obtained through sensitivity analysis in accordance to actual specimen geometry and clamping condition. Non-linear isotropic hardening rule with von Mises yield criterion and temperature-dependent material properties was implemented into the simulation which were generated by means of advanced material modelling software based on elemental composition of evolved component characterized using SEM/EDX. For numerical and experimental validation purpose, substrate deformation was measured using coordinate measurement machine before and after the process. It can be concluded that the result of the computed substrate deformation showed an acceptable agreement compared to experiment within the range of error between 0.5 and 27.5% at each specific measurement points and 10.1% as average single error. This basic investigation can be enhanced in the case where cost-effective WAAM application with dissimilar materials towards single-piece substrate component is concerned. [ABSTRACT FROM AUTHOR]

Coal mining results in strata movement and surrounding rock failure. Eventually, manual mining space will be occupied by the destructed coal rock, making it difficult to conduct field tests of the coal seam to explore gas seepage and transport patterns. Therefore, computational fluid dynamics (CFD) numerical computation is an important tool for such studies. From the aspect of gas pre-drainage, for layer-through boreholes in the floor roadway of the 8,406 working face in Yangquan Mine 5 in China, reasonable layout parameters were obtained by CFD optimization. For effectively controlling the scope of boreholes along coal seam 9 in the Kaiyuan Mine, CFD computation was performed. The results revealed that the horizontal spacing between boreholes should be ≤2 m when a tri-quincuncial borehole layout is used. Optimization of the surface well position layout for the fault structure zone in the Xinjing Mine of the Yangquan mining area indicated that the horizontal distance between the surface well and the fault plane should be <150 m. From the aspect of gas drainage with mining-induced pressure relief, CFD computation was performed for pressure-relieved gas transport in the K8205 working face of Yangquan Mine 3. The results showed that forced roof caving should be used before the overhang length of hard roof reaches 25 m in the K8205 working face to avoid gas overrun. From the aspect of gas drainage from the abandoned gob, surface well control scopes at different surface well positions were computed, and an O-ring fissure zone is proposed as a reasonable scope for the surface well layout. CFD computation has been widely applied to coal and gas co-extraction in the Yangquan mining area and has played a significant role in guiding related gas drainage engineering practice. [ABSTRACT FROM AUTHOR]

In the presented research article, the intelligence based numerical computation of artificial neural network backpropagated with Levenberg-Marquardt algorithm has been developed to analyze the novel ferrofluid flow model in the presence of magnetic dipole. Heat transfer effects are also incorporated along the horizontal. The designed fluid flow model initially represented by system of partial differential equations are converted into system of non-linear ordinary differential equations through suitable similarity transformations. The reference dataset of the possible outcomes is obtained from Adam numerical solver for the different scenarios of flow model by variation of co-efficient of the thermal expansion, Eckert number, suction parameter, magnetization and radiation parameter. The approximated solutions are interpreted for designed model by testing, training and validation process of backpropagated neural networks. Furthermore, the comparative studies and performance analysis of used algorithm is validated through regression analysis, histogram studies, correlation index and results of mean square error. [ABSTRACT FROM AUTHOR]

Discretization of the two dimensional nonlinear shallow water equations is done using pseudo-spectral methods with a translating vortex test case. First, the equations are modeled using Chebyshev differentiation with Fast Fourier Transform. The test case is an exact solution of the shallow water equations which is a traveling vortex defined by constants of any value. The equations are integrated using Euler and Leapfrog time stepping methods and convergence of the solutions is computed using the infinite norm. Second, this solution is compared to discretization of the equations using the method of integrating factors and fourth order Runge-Kutta for integration. The method of integrating factors uses the zero-padding technique for anti-aliasing of the nonlinear terms. The solution’s streamlines are also compared to that of the true solution to test for accuracy and determine the direction of the flow. A second test case is a perturbation of fluid for specific times. Results at .02 seconds show that the Chebyshev differentiation method can produce first and third order convergence using the Euler and Leapfrog methods and the Integrating factor method is able to construct a solution after de-aliasing.

The current study delivers a numerical investigation on the performance of heat transfer and flow of micropolar fluid in porous Darcy structures with isothermal and isoflux walls (boundary conditions) of a stretching sheet. The dynamics and mechanism of such fluid flows are modelled by nonlinear partial differential equations that are reduced to a system of nonlinear ordinary differential equations by utilizing the porosity of medium and similarity functions. Generally, the explicit or analytical solutions for such nonlinear problems are hard to calculate. Therefore, we have designed a computer or artificial intelligence-based numerical technique. The reliability of neural networks using the machine learning (ML) approach is used with a local optimization technique to investigate the behaviours of different material parameters such as the Prandtl number, micropolar parameters, Reynolds number, heat index parameter, injection/suction parameter on the temperature profile, fluid speed, and spin/rotational behaviour of the microstructures. The approximate solutions determined by the efficient machine learning approach are compared with the classical Runge–Kutta fourth-order method and generalized finite difference approximation on a quasi-uniform mesh. The accuracy of the errors lies around 10−8 to 10−10 between the traditional analytical solutions and machine learning strategy. ML-based techniques solve different problems without discretization or computational work, and are not subject to the continuity or differentiability of the governing model. Moreover, the results are illustrated briefly to help implement microfluids in drug administering, elegans immobilization, and pH controlling processes.

This research is devoted to numerical and experimental analysis on deformation of completely removed component induced by wire arc additive manufacturing (WAAM). The component has the form of a hollow and rectangular thin wall made of deposition layer of stainless steel SS316L on top of substrate plate of mild steel S235. In this research, thermomechanical finite element analysis was applied with Goldak's double ellipsoid as heat-source model and isotropic hardening rule based on von-Mises yield criterion. A specialized numerical simulation software Simufact.Welding 2021 (SW) was utilized in developing the numerical model and the simulation of process enhanced with separation and deposition algorithm to predict the component deformation after removal of substrate. On determining the best possible mesh size, a sensitivity analysis was conducted before the advanced stage of model development. An advanced material modeling, the data of which were obtained based on the chemical composition of the evolved SS316L sample, was developed using an advanced material modeling software JMATPRO. For verification purpose, a series of WAAM experiments using robotic GMAW with synergic power source were conducted followed by the removal of substrate from component using machining process. Furthermore, component distortion was measured using industrial noncontact 3D scanner with structured blue light to fully capture the upper section deformation and compared with result of numerical computation. It can be concluded that this novel distortion analysis method using thermomechanical numerical computation with evolved material property and modified algorithms for substrate removal exhibits a surface deviation in vertical direction between 0.05 and 2.16 mm with acceptable pointwise and average error percentage of up to 3%., (Copyright 2023, Mary Ann Liebert, Inc., publishers.)

This paper is dealing with an investigation using nonlinear numerical computation for manufacturing to predict substrate distortion induced by a hollow-shaped Wire Arc Additive Manufacturing (WAAM) process. The WAAM component is designed in a thin-walled rectangular form consisting of twenty-five deposited layers with austenitic stainless-steel wire SS316L as feedstock and SS304 as substrate material. In this investigation, two different material models were investigated which was directly retrieved from numerical computation or virtual manufacturing software database and evolved component material composition obtained from experiment and characterized using Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray (EDX) analysis as well as generated using advanced modelling software JMATPRO for creating new properties including the flow curves. The hollow shape is modelled based on simplified rectangular mesh geometry with identical specimen dimension during experiment. A coupled thermomechanical solution is adopted including phase-change phenomena defined in latent heat, whereby temperature history due to successive layer deposition is simulated by coupling the heat transfer and mechanical analysis. Further, transient thermal distribution is calibrated from experiment obtained from thermocouple analysis at two reference measurement locations. New heat transfer coefficients are to be adjusted to reflect actual temperature change. Prior to simulation execution, a sensitivity analysis was conducted in order to find the optimal number of elements or mesh size towards temperature distribution. Based on these boundary conditions, WAAM distortion is verified using robotic welding system equipped with pulsed power source. The experimental substrate distortion is measured on various points prior to and after the process. It can be concluded based on the adjusted model and experimental verification that using nonlinear numerical computation, the prediction of substrate distortion with evolved material property of component yields closer average result within the relative error less than 11% compared to database material giving doubled inaccuracy up to 22%. [ABSTRACT FROM AUTHOR]

Copyright of Journal of China University of Petroleum is the property of China University of Petroleum and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This article examines entropy production (EP) of magneto-hydrodynamics viscous fluid flow model (MHD-VFFM) subject to a variable thickness surface with heat sink/source effect by utilizing the intelligent computing paradigm via artificial Levenberg–Marquardt back propagated neural networks (ALM-BPNNs). The governing partial differential equations (PDEs) of MHD-VFFM are transformed into ODEs by applying suitable similarity transformations. The reference dataset is obtained from Adam numerical solver by the variation of Hartmann number (Ha), thickness parameter (α) , power index (n) , thermophoresis parameter (Nt), Brinkman number (Br), Lewis number (Le) and Brownian diffusion parameter (Nb) for all scenarios of proposed ALM-BPNN. The reference data samples arbitrary selected for training/testing/validation are used to find and analyze the approximated solutions of proposed ALM-BPNNs as well as comparison with reference results. The excellent performance of ALM-BPNN is consistently endorsed by Mean Squared Error (MSE) convergence curves, regression index and error histogram analysis. Intelligent computing based investigation suggests that the rise in values of Ha declines the velocity of the fluid motion but converse trend is seen for growing values of n. The rising values of Ha, Nt and Br improve the heat transfer but converse trend is seen for growing values of α. The inclining values of Nt incline the mass transfer but it shows reverse behavior for escalating values of Le. The inclining values of Br incline the EP. [ABSTRACT FROM AUTHOR]

The response of light in a nonlinear dispersive medium is governed by the nonlinear Schrödinger equation (NLSE). In general, for higher order group velocity dispersion (GVD) with frequency-dependent gain or absorption, NLSE is numerically solved using the split-step Fourier method. Extended NLSEs including the effects of higher order GVD, frequency-dependent gain and frequency-dependent absorption comprise higher order derivative terms. In this paper, an algorithm to solve partial differential equations with any higher order derivative term is described. A program based on this algorithm was used to solve optical pulse propagation equations in a nonlinear medium with higher order GVD, frequency-dependent gain and saturable absorption. [ABSTRACT FROM AUTHOR]

On the basis of air heater characteristics, a new computational model was developed in this paper, which was aimed at investigating acoustics and instabilities in air heaters. This model included the effects of mean flow, viscosity, entropy waves, non-linear acoustics and realistic boundary conditions. In addition, it was practical for air heaters with hundreds of injectors, complex configurations and geometries. Analytical solutions of acoustics in a closed rectangular cavity were used to verify and validate the computational model. It was shown that the predicted critical parameters of air heater agreed well with the experimental data or design values. This model predicted the self-excited spinning tangential modes without any preliminary assumptions about them. Traditional combustion response function assumes that combustion mainly takes place in a so-called rapid combustion zone, and this zone is usually modelled as a disc in the combustor near the injection head. However, in practice, the flame has a spatial distribution. This paper described the effect of flame spatial distribution on predictions of oscillation frequency and mode. It was found that frequency and mode shape of oscillations closely depended on the length of the heat release zone. Comparison of different heat release zones indicated that the increment of heat release length exhibited an increased tendency toward lower-order longitudinal modes, when the heat release zone was located near the faceplate where it was the pressure antinode of the longitudinal mode. Modulation of heat release length might cause bifurcations between standing and turning modes. A noticeable tendency was toward higher-order standing tangential mode with increasing heat release length. Finally, theoretical analysis of the modal behaviour, i.e. standing or spinning waves, was performed. [ABSTRACT FROM AUTHOR]

It has been suggested in the literature that the sound velocity of the nuclear matter v s exceeds the so-called sound velocity bound v s ≤ c / 3 at high density, where c is the speed of light. In this paper, we revisit the issue of neutron star properties, comparing current measurements of mass, radius, and tidal deformability with 1 0 5 different equations of state. These equations are parametrized at low density and saturate the sound velocity bound beyond twice the saturation density. This allows us to conservatively determine the maximum mass compatible with observed neutron star properties and the sound velocity bound. We find that majority of the models are eliminated by the incompatibility with the observations and, especially, the recently detected massive pulsar (2. 35 ± 0. 17 M ⊙ ) is hardly realized by our simulations. Our study strongly supports that the sound velocity bound is not satisfied in nature. • Robust determination of maximal NS mass consistent with sound velocity bound. • Using an EoS that marginally meets the sound velocity bound at high densities. • Use of 105 equations of states for comparing different properties of NS [ABSTRACT FROM AUTHOR]

In this paper, numerical computations are carried out to investigate the seismo-electromagnetic signals arising from the motional induction effect due to an earthquake source embedded in 3-D multi-layered media. First, our numerical computation approach that combines discrete wavenumber method, peak-trough averaging method, and point source stacking method is introduced in detail. The peak-trough averaging method helps overcome the slow convergence problem, which occurs when the source–receiver depth difference is small, allowing us to consider any focus depth. The point source stacking method is used to deal with a finite fault. Later, an excellent agreement between our method and the curvilinear grid finite-difference method for the seismic wave solutions is found, which to a certain degree verifies the validity of our method. Thereafter, numerical computation results of an air–solid two-layer model show that both a receiver below and another one above the ground surface will record electromagnetic (EM) signals showing up at the same time as seismic waves, that is, the so-called coseismic EM signals. These results suggest that the in-air coseismic magnetic signals reported previously, which were recorded by induction coils hung on trees, can be explained by the motional induction effect or maybe other seismo-electromagnetic coupling mechanisms. Further investigations of wave-field snapshots and theoretical analysis suggest that the seismic-to-EM conversion caused by the motional induction effect will give birth to evanescent EM waves when seismic waves arrive at an interface with an incident angle greater than the critical angle θc = arcsin(Vsei/Vem), where Vsei and Vem are seismic wave velocity and EM wave velocity, respectively. The computed EM signals in air are found to have an excellent agreement with the theoretically predicted amplitude decay characteristic for a single frequency and single wavenumber. The evanescent EM waves originating from a subsurface interface of conductivity contrast will contribute to the coseismic EM signals. Thus, the conductivity at depth will affect the coseismic EM signals recorded nearby the ground surface. Finally, a fault rupture spreading to the ground surface, an unexamined case in previous numerical computations of seismo-electromagnetic signals, is considered. The computation results once again indicate the motional induction effect can contribute to the coseismic EM signals. [ABSTRACT FROM AUTHOR]

This paper considers the problem associated with the numerical simulation of the interaction between the cocurrent stream occurring near a monoblock moving in the gas medium and solid fuel combustion products flowing from a solid fuel rocket engine (SFRE). The peculiarity of the approach used is the description of gas-dynamic processes inside the combustion chamber, in the nozzle block, and the down jet based on a single calculation methodology. In the formulated numerical methodology, the calculation of gas-dynamic parameters is based on the solution of unsteady Navier–Stokes equations and the application of a hybrid computational grid. A hybrid block-structured computational grid makes it possible to calculate gas flow near bodies of complex geometric shapes. The simulation of the main phase of interaction, corresponding to the stationary mode of rocket flight in the Earth’s atmosphere, has been carried out. A conjugated simulation of the internal ballistics of SFRE and interaction of combustion products jets is conducted.

Based on the theory of symbolic dynamical systems, we propose a novel computation method to locate and stabilize the unstable periodic points (UPPs) in a two-dimensional dynamical system with a Smale horseshoe. This method directly implies a new framework for controlling chaos. By introducing the subset based correspondence between a planar dynamical system and a symbolic dynamical system, we locate regions sectioned by stable and unstable manifolds comprehensively and identify the specified region containing a UPP with the particular period. Then Newton's method compensates the accurate location of the UPP with the regional information as an initial estimation. On the other hand, the external force control (EFC) is known as an effective method to stabilize the UPPs. By applying the EFC to the located UPPs, robust controlling chaos is realized. In this framework, we never use ad hoc approaches to find target UPPs in the given chaotic set. Moreover, the method can stabilize UPPs with the specified period regardless of the situation where the targeted chaotic set is attractive. As illustrative numerical experiments, we locate and stabilize UPPs and the corresponding unstable periodic orbits in a horseshoe structure of the Duffing equation. In spite of the strong instability of UPPs, the controlled orbit is robust and the control input retains being tiny in magnitude. [ABSTRACT FROM AUTHOR]

This fundamental research deals with the investigation of material property model influences on distortion induced by multi-layered Wire Arc Additive Manufacturing (WAAM) with synergic-pulsed gas metal arc welding (P-GMAW) process which was modelled and simulated by means of non-linear numerical computation. The material property models of stainless steel SS316L component to be compared stem from three different sources namely existing database, initial wire and evolved component. The new property models were generated with advanced material modelling software JMATPRO based on chemical compositions analysed at initial wire and component using SEM–EDX. The flow curve for each material model was taken with the strain rates ranging from 0.001 to 1.0 s−1. In the numerical simulation, a coupled thermomechanical solution was adopted including phase-change phenomena defined in latent heat. Goldak’s double ellipsoid was applied as heat source model and simplified rectangular bead with hexagonal element type and meshing was developed to avoid extensive pre-processing effort and to reduce the computational time at post-processing level. Temperature behaviour due to the successive layer deposition was simulated considering heat transfer effect coupled to mechanical analysis. The adjustment of simulative transient to experimental thermal distribution lead to new fitted heat transfer coefficient. Prior to execution of numerical simulation, a sensitivity analysis was conducted to find the optimal number of elements or mesh size towards maximum reached temperature. It can be concluded based on the adjusted model, selected mesh size and experimental validation that numerical computation of substrate distortion with evolved material property of component and initial wire of SS316L yield closer average result within the relative error ranging between 11 and 16% compared to database material giving more than 22%. [ABSTRACT FROM AUTHOR]

The magnetic suspension wind tunnel balance (MSBS) is an entirely new device for aerodynamic measurement, and it makes the best of the electromagnetic force to suspend the aircraft model in the wind tunnel without contact. Compared with conventional wind tunnel balance, it absolutely abandons the model support and airflow interference. Therefore, the aerodynamic measurement environment is more authentic and the aerodynamic measurement results are more accurate. The electromagnetic field in MSBS plays a major role in bearing the force of wind. The numerical computation and finite element numerical analysis are performed to investigate key factors of electromagnetic force under different conditions. The calculation results based on finite element method (FEM) have revealed that the diameter and the spacing of of the axial coil, the number of segments and the pitch angle of the suspension model are key factors of electromagnetic force. Based on the above key factors, the structure of the magnetic suspension balance is optimized to maximize the electromagnetic force under multiple constraints. [ABSTRACT FROM AUTHOR]

Financial data sets are growing too fast and need to be analyzed. Data science has many different techniques to store and summarize, mining, running simulations and finally analyzing them. Among data science methods, predictive methods play a critical role in analyzing financial data sets. In the current paper, applications of 22 methods classified in four categories namely data mining and machine learning, numerical analysis, operation research techniques and meta-heuristic techniques, in financial data sets are studied. To this end, first, literature reviews on these methods are given. For each method, a data analysis case (as an illustrative example) is presented and the problem is analyzed with the mentioned method. An actual case is given to apply those methods to solve the problem and to choose a better one. Finally, a conclusion section is proposed. [ABSTRACT FROM AUTHOR]

The incompressible miscible displacement of three-dimensional Darcy–Forchheimer flow is discussed in this paper, and the mathematical model is formulated by two partial differential equations, a Darcy–Forchheimer flow equation for the pressure and a convection-diffusion equation for the concentration. The pressure plays an important role and determines the Darcy–Forchheimer velocity. A conservative mixed finite element is used to approximate the pressure and the velocity, and the computational accuracy of Darcy–Forchheimer velocity is improved by one order. A second-order upwind fractional step difference scheme is adopted to obtain the concentration, and numerical oscillation and dispersion are eliminated. Computational work is reduced greatly by decomposing the whole computation into successive one-dimensional subcomputations, where the speedup solvers are used. Applying energy-norm method, operator decomposition, speedup algorithm and induction hypotheses, we derive an optimal second-order estimates in L 2 norm. Numerical experiments are given to show the theoretical accuracy and the applicability for solving actual problems. [ABSTRACT FROM AUTHOR]

For the heat exchange verification, the averaged behavior of heat transfer in the vortex matrices with a channel wedging angle of 4.5 deg is compared with the results obtained in the experimental conditions of zinc thermostat. As a result of 3D calculation in the ANSYS CFX, the local heat transfer coefficients and hydrodynamics behavior are obtained for the vortex matrix models when the wedging angle is changed from 4.5 to 17 deg [ABSTRACT FROM AUTHOR]

The doubly non-central F distribution is a widely applied probability distribution. The cumulative distribution function (CDF) of the doubly non-central F distribution can be expressed using the infinite doubly series. In this paper, a CDF calculation method that allows for controlled precision is derived through the study of the infinite doubly series. By setting parameters, this method can provide an upper limit of error for the computed results, thereby allowing for precision control in the calculations. Experimental results demonstrate that this method achieves a good balance between computational precision and speed., Competing Interests: The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Yinhua Tian reports financial support and writing assistance were provided by 10.13039/501100001809National Natural Science Foundation of China (72101137). Yinhua Tian reports financial support and writing assistance were provided by 10.13039/501100007129Natural Science Foundation of Shandong Province (ZR2021MF117). Yinhua Tian reports financial support and writing assistance were provided by Education Ministry Humanities and Social Science Research Youth Fund Project of China (21YJCZH150). If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Author(s).)

Microphysiological systems have potential as test systems in studying the intestinal barrier, in which shear stress is critical for the differentiation of Caco-2 cells into enterocytes. The most commonly used in vitro gut model for intestinal barrier studies is based on trans-well cultures. Albeit useful, these culture systems lack physiological shear stress which is believed to be critical for the differentiation of Caco-2 cells into enterocytes and to form tight monolayers. Conversely, organ-on-chip models have presented themselves as a promising alternative since it provides cells with the required shear stress. To this end, a novel biocompatible 3D-printed microfluidic device was developed. In this device, Caco-2 cells were seeded under physiologically-relevant unidirectional shear stress and compared to cells cultured under gravity-driven flow. Using numerical studies, the flow rate that corresponds to the required shear stress was calculated. Experimental tests were conducted to verify the effect of this on cell differentiation. The experiments clearly showed an enhancement of cell differentiation potential in a unidirectional physiologically-relevant pump-driven flow system (PDFS) as opposed to the simpler bidirectional gravity-driven flow system (GDFS). Additionally, computational modeling of an adapted design confirmed its ability to supply all cells with a more homogeneous shear stress, potentially further enhancing their differentiation. The shear stress in the adapted design can be well-approximated with analytic methods, thus allowing for efficient predictions for all parameter values in the system. The developed novel microfluidic device led to the formation of a tighter monolayer and enhanced functional properties of the differentiated Caco-2 cells, which presents a promising tool for preclinical in vitro testing of drugs in an animal-free platform.

In terms of the stability of backfill and surrounding rock during the mining process of Stage open stoping with delayed backfill at Longwan Iron Mine，a similar simulation experiment was conducted to investigate the displacement field evolution of the stope and its surrounding rocks during the mining and filling processes.The backfilling stope was simplified into mechanical model of thin plate，which was imported into the platform of software COMSOL Multiphysics to carry out numerical analysis.The numerical computation results were compared with the similar simulation outcomes，and it was noticed that they agreed well with each other.This indicated that the evolution of displacement and strain obtained by numerical calculation accorded with the actual conditions basically.The results showed that the stope stability was closely related to the strength of ore body and backfill as well as the stope integrity.The displacement and strain field evolutions of the filling stope and its surrounding rocks obtained in this study can provide reference and data supporting for the mining and backfilling operations of similar mines.

Dispersion of the impact points of the unguided rockets is a consequence of disturbances, such as thrust misalignments, rocket asymmetry, manufactoring inacuracy, etc. Influence of some disturbances are most significant in the initial phase of flight when the rocket leaves the launcher due to the small velocity. This influence is minimized by rotation of the rockets in the launcher tube which in practice is realized by the guide pin connected to the rocket and groove in the launcher tube or by canted nozzles. Also the rotation of the rocket in the launching tube and in flight can be realized by canted fins foled in the nozzle when the rocket is in the launcher tube. These fins are deployed when the rocket leaves the tube and creates rocket rotation in free flight. The rolling moments of the rocket in the launcher tube and during free flight are calculated by CFD simulation. The CFD simulation is also used for calculation of the fin hinge moment generated by exaust gases from rocket motor which is required for deployement of the fins when the rocket leaves the launcher tube. The roll rate required for minimization of the rocket dispersions and roll rate in the launcher tube for various cant angle of the fins are calculated by 6DOF numerical simulation. The results of simulation are used to select the best value of the fins cant angle.

The quenching limits of small-scale H 2 diffusion flame achieved by microtubes were studied experimentally and numerically. The experimental observation shows that the luminosity of small-scale H 2 diffusion flame becomes ambiguous with decreasing fuel jet velocity. However, the OH radical in the flame can be detected clearly by using the planar laser-induced fluorescence (PLIF) measurement. The quenching limits of small-scale H 2 diffusion flames at different inner tube diameters were obtained by OH-PLIF measurement and numerical computation with a detailed chemical mechanism. The computed and measured quenching limits show good agreement. The results show that the quenching mass flow rate decreases gradually with decreasing inner tube diameter. A power function relationship exists between the quenching mass flow rate and the inner tube diameter. The analysis of the computational results reveals that the quenching mass flow rate depends on the ratio between heat generation and heat loss, net fuel consumption ratio, the lower heating value of the fuel and total heat loss from the reaction-part of the flame. The decrease in the diameter of the reaction-part of the flame with decreasing inner tube diameter leads to a smaller quenching mass flow rate. • Quenching limits of small-scale H 2 diffusion flames are measured by using OH-PLIF. • Quenching limits of the H 2 flames are obtained by 2-D numerical computation. • The near-quenching small-scale H 2 flames have similar combustion characteristics. • The conductive heat loss is the primary reason for the quenching of small H 2 flame. • The quenching mass flow rate is proportion to the surface area of the reaction-part. [ABSTRACT FROM AUTHOR]