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Little seems to be considered about the globally exponentially asymptotical stability of parabolic type equilibria and the existence of heteroclinic orbits in the Lorenz-like system with high-order nonlinear terms. To achieve this target, by adding the nonlinear terms yz and x 2 y to the second equation of the system, this paper introduces the new 3D cubic Lorenz-like system: x ˙ = a (y - x) , y ˙ = b 1 y + b 2 y z + b 3 x z + b 4 x 2 y , z ˙ = - c z + y 2 , which does not belong to the generalized Lorenz systems family. In addition to giving rise to generic and degenerate pitchfork bifurcation, Hopf bifurcation, hidden Lorenz-like attractors, singularly degenerate heteroclinic cycles with nearby chaotic attractors, etc., one still rigorously proves that not only the parabolic type equilibria S x = { (x , x , x 2 c) | x ∈ R , c ≠ 0 } are globally exponentially asymptotically stable, but also there exists a pair of symmetrical heteroclinic orbits with respect to the z-axis, as most other Lorenz-like systems. This study may offer new insights into revealing some other novel dynamic characteristics of the Lorenz-like system family. [ABSTRACT FROM AUTHOR]

In the process of internal thread cold extrusion, the extrusion tap is an indispensable tool. Therefore, it is important to improve the service life of the extrusion tap and reduce the tool wear. In this paper, using Central Composite Design response surface test, the influence of the parameters (including the guide cone angle, backhoe capacity, guide cone length and working cone length) of the extrusion tap on the forming quality of internal cold extrusion are investigated, so as to obtain the minimum extrusion torque and the minimum extrusion temperature. A polynomial regression response model of the minimum extrusion torque and minimum extrusion temperature is obtained. Using the regression model, the objective function is optimized, and a group of optimal parameters is obtained (guide cone angle: 10°, backhoe capacity: 0.32, guide cone length: 4 mm, and working cone length: 13 mm). Numerical simulation of the optimal parameters is also carried out. The results show that the measured extrusion torque and extrusion temperature are close to the predicted values with errors of 2 and 2.55%, respectively, which are well fitted by the model. [ABSTRACT FROM AUTHOR]

This paper aims to address a challenging problem of a drone swarm for a specific mission by reaching a desired region, through an unknown environment. A bio-inspired flocking algorithm with adaptive goal-directed strategy (AGDS) is proposed and developed for the drones swarmed across unknown environments. Each drone employs a biological visual mechanism to sense obstacles in within local perceptible scopes. Task information of the destination is only given to a few specified drones (named as informed agents), rather than to all other individual drones (uninformed agents). With the proposed flocking swarm, the informed agents operate collectively with the remaining uninformed agents to achieve a common and overall mission. By virtue of numerical simulation, the AGDS and non-adaptive goal-directed strategy (non-AGDS) are both presented and evaluated. Experiments by flying six DJI Tello quadrotors indoor are conducted to validate the developed flocking algorithm. Additional validations within canyon-like complicated scenarios have also been carried out. Both simulation and experimental results demonstrate the efficiency of the proposed swarm flocking algorithm with AGDS. [ABSTRACT FROM AUTHOR]

In this paper, a simple memcapacitors-based oscillator, set up from the Colpitts' LC tank circuit is presented. The oscillator is designed by replacing the two normal capacitors of Colpitts' tank circuit with two nonlinear memcapacitors. The new resulting nonlinear circuit consists of only three dynamic elements, including two memcapacitors blocks and an inductor. The model is described as a continuous-time three-dimensional autonomous system with cubic nonlinearities. The structure of the equilibrium points and the discrete symmetries of the model equations are discussed. One of the key contributions in this area is the introduction of a simple circuit presenting peculiar behaviors such as offset bossing and coexisting of multiple attractors. An appropriate electronic circuit (analog simulator) is proposed to investigate the dynamic behavior of the proposed system and prove its feasibility. The proposed oscillator enriches the literature on simple memcapacitor-based circuits with complex dynamic behavior. [ABSTRACT FROM AUTHOR]

Dynamic environments challenge existing robot navigation methods, and motivate either stringent assumptions on workspace variation or relinquishing of collision avoidance and convergence guarantees. This paper shows that the latter can be preserved even in the absence of knowledge of how the environment evolves, through a navigation function methodology applicable to sphere-worlds with moving obstacles and robot destinations. Assuming bounds on speeds of robot destination and obstacles, and sufficiently higher maximum robot speed, the navigation function gradient can be used produce robot feedback laws that guarantee obstacle avoidance, and theoretical guarantees of bounded tracking errors and asymptotic convergence to the target when the latter eventually stops moving. The efficacy of the gradient-based feedback controller derived from the new navigation function construction is demonstrated both in numerical simulations as well as experimentally. [ABSTRACT FROM AUTHOR]

In this paper, we perform the numerical modelling of lower-band VLF chorus in the earth's magnetosphere. Assuming parallel propagation the 1d3v code has one spatial dimension z along the ambient magnetic field, which has a parabolic z dependence about the equator. The method used is Vlasov Hybrid Simulation (VHS) also known in the literature as the method of Kinetic Phase Point Trajectories (Nunn in Computer Physics Comms 60:1–25, 1990, J Computational Phys 108(1):180–196, 1993; Kazeminezhad et al. in Phys Rev E67:026704, 2003). The method is straightforward and easy to program, and robust against distribution function filamentation. Importantly, VHS does not invoke unphysical smoothing of the distribution function. Previous versions of the VLF/VHS code had a narrow bandwidth ~ 100 Hz, which enabled simulation of a wide variety of discrete triggered emissions. The present quasi-broadband VHS code has a bandwidth of ~ 3000 Hz, which is far more realistic for the simulation of chorus in its entirety. Further, the quasi-broadband code does not require artificial saturation, and does not need to employ matched filtering to accommodate large spatial frequency gradients. The aim of this paper which has been achieved is to produce VLF chorus Vlasov simulations employing a systematic variety of triggering input signals, namely key down, single pulse, PLHR, and broadband hiss. [ABSTRACT FROM AUTHOR]

Mining-induced stress will cause the change of coal seam pore structure. However, most coal seam infusion simulation studies do not consider the change of pore with mining-induced stress. In order to study the impact of mining-induced stress on coal seam infusion, this paper used the triaxial compression test of coal as the basis to establish the relationship equation between volume strain and stress loading by the volume deformation table, and then introduced the relationship equation into FLUENT through Fluent Custom Function (UDF). Taking the mining time and water injection time as the axis, this paper compared and analyzed the variation law of coal seam infusion seepage parameters with coal seams with pore changes caused by mining-induced stress (model I) and traditional fixed porosity (model II). The results show that in the elastic deformation stage, the mining-induced stress makes the original pores of the coal seam compact, so that the water injection seepage pressure, seepage velocity, and water content volume of model I are lower than those of model II. In the plastic deformation and post-peak deformation stages, mining-induced stress promotes the development of coal seam pores, and the water injection seepage pressure, seepage velocity, and water content of model I gradually exceed the seepage field parameters of model II. It can be seen that mining-induced stress has an important impact on water injection seepage. The simulation method proposed in this paper can more truly reflect the impact of actual mining process on coal seam infusion seepage. [ABSTRACT FROM AUTHOR]

In the last decade there has been an explosion of interest in mining time series data. Literally hundreds of papers have introduced new algorithms to index, classify, cluster and segment time series. In this work we make the following claim. Much of this work has very little utility because the contribution made (speed in the case of indexing, accuracy in the case of classification and clustering, model accuracy in the case of segmentation) offer an amount of 'improvement' that would have been completely dwarfed by the variance that would have been observed by testing on many real world datasets, or the variance that would have been observed by changing minor (unstated) implementation details. To illustrate our point, we have undertaken the most exhaustive set of time series experiments ever attempted, re-implementing the contribution of more than two dozen papers, and testing them on 50 real world, highly diverse datasets. Our empirical results strongly support our assertion, and suggest the need for a set of time series benchmarks and more careful empirical evaluation in the data mining community. [ABSTRACT FROM AUTHOR]

The use of cloud computing that provides resources on demand to various types of users, including enterprises as well as engineering and scientific institutions, is growing rapidly. An effective resource management middleware is necessary to harness the power of the underlying distributed hardware in a cloud. Two of the key operations provided by a resource manager are resource allocation (matchmaking) and scheduling. This paper concerns the problem of matchmaking and scheduling an open stream of multi-stage jobs (or workflows) with Service Level Agreements (SLAs) on a cloud or cluster. Multi-stage jobs require service from multiple system resources and are characterized by multiple phases of execution. This paper presents a resource allocation and scheduling technique called RM-DCWF: Resource Management Technique for Deadline-constrained Workflows that can efficiently matchmake and schedule an open stream of multi-stage jobs with SLAs, where each SLA is characterized by an earliest start time, an execution time, and a deadline. A rigorous simulation-based performance evaluation of RM-DCWF is conducted using synthetic workloads derived from real scientific workflows. In addition, the impact of various system and workload parameters on system performance is investigated. The results of this performance evaluation demonstrate the effectiveness of RM-DCWF as captured in a low number of jobs missing their deadlines. [ABSTRACT FROM AUTHOR]

This paper proposes a new multi-objective day-ahead market clearing (DAMC) mechanism with demand response offers, considering realistic voltage-dependent load modeling. This paper presents several objectives such as Social Welfare Maximization including demand response offers (SWM), Load reduction Minimization ( $${P}_{\mathrm{red}}{M}$$ ), and Load Served Error (LSE) minimization. Energy and demand-side reserves are cleared through co-optimization process. The proposed approach is particularly suitable for stressed system conditions, where demand elasticity alone cannot yield a feasible optimal solution. The feasible solution is obtained by invoking demand-response offers. Here, multi-objective Strength Pareto Evolutionary Algorithm 2+ (SPEA 2+) has been used to solve the proposed DAMC problem. This paper emphasizes the requirement for selecting judiciously, a combination of objectives best suitable for the DAMC. The effectiveness of proposed DAMC scheme is confirmed with the results obtained from IEEE 30 bus system. It is assumed that all the generators and loads participate in DAMC. Two different cases-one with constant load modeling and the other with the voltage-dependent load modeling-have been simulated at stressed loading conditions. When loads are modeled as the voltage dependent, then it is shown that SWM and $${P}_{\mathrm{red}}{M}$$ are not valid single or multiple objectives with this load model, due to reduction in load served. With voltage-dependent load modeling, SWM and LSE minimization are best suited objectives to be optimized simultaneously. The obtained Pareto optimal front allows system operator to make a better decision regarding compromise between the conflicting objective functions. [ABSTRACT FROM AUTHOR]

Field performance shows that the incremental oil recovery factor from alkaline projects was low. Chemical EOR experience tells us that the mobility control is very important. Thus, the combination of alkaline flooding and polymer flooding is expected to improve alkaline flooding performance. This paper is to provide a critical review of alkaline-polymer (AP) flooding. The following subjects are covered. The data and analysis presented in this paper will give readers updated information about alkaline-polymer flooding. This paper suggests the AP synergy need to be further studied with more experimental measurement, theoretical analysis and numerical simulation study. [ABSTRACT FROM AUTHOR]

In this paper, a simplified dynamic model is constructed to describe the main characteristic of electromagnetic micro-mirror. Then, based on the information provided by the derived simplified model, a model-guided extremum seeking control (MGESC) scheme with backtracking line search is developed, which can automatically estimate the best value of step-size at each search iteration to improve the performance of the control system for target tracking. Then, the convergence of the proposed MGES algorithm is proved. Finally, the experimental results and the simulations are presented to verify the proposed method. [ABSTRACT FROM AUTHOR]

Insensitive munition assessments are required to carry out sympathetic detonation experiments, in which detonation of an explosive charge triggers detonation of another, and a chain reaction subsequency starts. In this paper, a numerical simulation method is developed to predict the sympathetic detonation behavior of fuze explosive trains, which includes the ignition and growth model, the Jones–Wilkins–Lee equations of state, and the constitutive relationship. The sympathetic detonation behaviors of a fuze is studied for a single donor and a single acceptor. The causes of sympathetic detonation of the fuze explosive trains are analyzed for different fragment and shock wave loading conditions. A sympathetic detonation criterion in different modes of loading is established, which provides a theoretical model for predicting the relationship between the detonation sequence and the placement distance of the fuze. The conclusions obtained in this paper can provide a reference for studying sympathetic detonation of fuze conditions. [ABSTRACT FROM AUTHOR]

The article describes the simulation results of an unbalanced rotary machine with an automatic ball balancer with a deep chamber (ABB-DC) based on a mathematical model of such a system. The ABB chamber has a cylindrical shape and is filled with balls that can move freely in general motion. The model takes into account mutual collisions between the balls, as well as between the balls and the chamber. The model also includes friction forces and rolling resistance. The comparison of simulation results performed with two different construction types of the chamber, classic single-layer drum (ABB-SC) and ABB-DC, confirmed the better efficiency of the ABB-DC in the optimal range of the number of balls. The machine body movement was limited to planar motion. The correctness of such a limitation has been verified by analyzing waveforms of reaction forces of constraints and their moments. Waveforms were divided into transient and steady states. The results of the analysis indicate the additional constraints do not significantly affect machine body movements. However, this might affect the ball arranging process in the ABB chamber. The paper also presents details of performing numerical simulations based on the developed mathematical model and numerical tests to determine the optimal integration time-step. [ABSTRACT FROM AUTHOR]

This paper presents a new forming technology for manufacturing the AZ31 magnesium alloy thin-wall tube. The direct extrusion process and continuous shearing-bending process are combined to produce thin-wall magnesium tube, abbreviated as "TESB" (tube extrusion-shearing-bending). The process has been studied based on the combination of experiments and numerical simulations, and the influences of temperatures, extrusion stresses, and friction factors on the forming process have been studied by Deform-3D simulation. And the mechanical properties and the grain size of the formed product have been tested. TESB technology has been proved to refine the grains of magnesium alloy tube effectively, and the mechanical property of the product can be improved. The better experimental extrusion conditions were also obtained by simulation, and the properties of the products under the condition of lubrication were better when the temperature was 400°C. Three-dimensional finite element modeling is used to investigate the plastic deformation behaviors of wrought magnesium alloy during TESB process. Numerical results indicate TES could increase the cumulative strains effectively by direct extrusion and additional shearings. Experiments show that microstructures of magnesium alloy fabricated by TESB process can be refined to 50% of the original grain size with more uniform distribution. TES process could improve hardness of magnesium alloy obviously by comparing with which fabricated by direct extrusion. [ABSTRACT FROM AUTHOR]

Array imperfections severely degrade the performance of most physics-driven direction-of-arrival (DOA) methods. Deep learning-based methods do not rely on any assumptions, can learn the latent data features of a given dataset, and are expected to adapt better to array imperfections compared with existing physics-driven methods. Hence, an improved DOA estimation method based on long short-term memory (LSTM) neural networks for situations with array imperfections is proposed in this paper. Various analyses given by this paper demonstrate that the phase features are the key to DOA estimation. Considering the sequential characteristics of the moving target and the correlation of multi-frame data features, the LSTM neural networks are used to learn and enhance the phase features of sampled data. The DOA estimation accuracy and generalization capability are improved by mitigating the phase distortion using LSTM. Numerical simulations and statistical results show that the proposed method is satisfactory in terms of both the generalization capability and imperfection adaptability compared with state-of-the-art physics-driven and data-driven methods. [ABSTRACT FROM AUTHOR]

The present paper is dealt with a predator–prey model in which the growth of the prey population is influenced by the Allee effect while the predator species are contended with the prey population following the Crowley–Martin type response function. The proposed model is comprehensively analyzed in terms of stability and manifestation of bifurcation of the system. The system unveils the bi-stability together with the existence of a separatrix. In view of the eminence of spatial ecology, the dynamical complexity emanating from the induction of the Allee effect in prey species of a Crowley–Martin reaction–diffusion predator–prey model is also investigated profoundly. The results of numerical simulations reveal that the present system dynamics is motivated by both the Allee effect and diffusion-controlled pattern formation growth to hot spots, stripe-hot spot mixtures, stripes, labyrinthine, stripe-cold spot mixtures, and cold spots replication. The theoretical consequences of the spatiotemporal model under study are validated through numerical simulations. [ABSTRACT FROM AUTHOR]

Thin-walled tubular parts with longitudinal ribs are important lightweight components. To manufacture the complex shape, incremental forming processes like flow forming are increasingly used. However, it is still difficult to form deep longitudinal ribs by conventional flow forming like ball spinning (BS). This paper proposes a novel flow forming process named two-stage flow forming (TSFF) to manufacture the thin-walled tubular parts with deep longitudinal outer ribs. The TSFF process includes two forming stages of preforming and final forming. During the preforming stage, the balls make axially feed movement, which force the metal to flow radially, and preform the longitudinal outer ribs. In the final forming process, the balls make axial feed movement and the blank makes rotation, which forces the metal to flow along circumferential and radial direction. Thus, the wall thickness is reduced, and the deep longitudinal outer ribs are formed. Based on numerical simulation, the forming geometrical dimension by BS and TSFF is compared, and the forming effect of TSFF is better. To make further analysis of metal flow behavior, it can be found that TSFF promotes the metal to flow along tangential and radial direction, while restraining the axial flow of the metal, and finally improve the filling effect of the longitudinal outer ribs. In addition, the key process parameters of TSFF were studied, and it was found that the reduction of preforming and ball diameter had great influence on the filling effect of the outer ribs. Finally, the TSFF experiment is carried, and the result shows that thin-walled tubular parts with deep longitudinal outer ribs formed by TSFF are feasible. This study provides theoretical and experimental support for the development of the novel flow forming process. [ABSTRACT FROM AUTHOR]

This paper introduces a single-phase multi-function converter (MFC) circuit that can perform the power electronics functions of a DC–DC, a DC–AC, an AC–AC, and an AC–DC boost converter. The power circuit of the proposed converter contains only four bi-directional switches, which is sufficient side by side with a switched logic-based control system to execute converter functions. The proposed converter can implement the boosting converter function, which is a drawback of the conventional single-phase matrix converter, which is limited to performing the buck converter functions. The mathematical analysis of each converter function is presented. A state space averaging technique is employed to obtain the time-invariant state space model for a better understanding of the converter characteristics. The frequency response approach is used to demonstrate the effect of circuit parameters on converter stability using the time-invariant state-space model. Moreover, the performance analysis of the system is checked through the building of a simulation model of the proposed converter via MATLAB/Simulink and MATLAB/Simscape toolbox integration. Additionally, the actual performance of the proposed converter is verified through a laboratory prototype experimental study. The experimental results confirm those obtained by computer simulation, clearly demonstrating the successful operation of the proposed circuit as a multi-function converter with acceptable levels of total harmonic distortion (THD). [ABSTRACT FROM AUTHOR]

Drilling and blasting methods have been used as a common driving technique for shallow-hole driving and blasting in rock roadways. With the advent of digital electronic detonators and the need for increased production efficiency, the traditional blasting design is no longer suitable for deep hole blasting. In this paper, a disperse charge cut blasting method was proposed to address the issues of low excavation depth and high block rate in deep hole undercut blasting. First, a blasting model was used to illustrate the mechanism of the deep hole dispersive charge cut blasting process. Then, continuous charge and dispersed charge blasting models were developed using the smooth particle hydrodynamics-finite element method (SPH-FEM). The cutting parameters were determined theoretically, and the cutting efficiency was introduced to evaluate the cutting effect. The blasting effects of the two charging models were analyzed utilizing the evolution law of rock damage, the number of rock particles thrown, and the cutting efficiency. The results show that using a dispersed charge improves the cutting efficiency by about 20% and the rock breakage for the deep hole cut blasting compared to the traditional continuous charge. In addition, important parameters such as cutting hole spacing, cutting hole depth and upper charge proportion also have a significant impact on the cutting effect. Finally, the deep hole dispersed charge cut blasting technology is combined with the digital electronic detonator through the field engineering practice. It provides a reference for the subsequent deep hole cutting blasting and the use of electronic detonators in rock roadways. [ABSTRACT FROM AUTHOR]

To improve the performance of identifying the block-sparse systems, firstly, a new sparsity aware block-sparse proportionate affine projection algorithm (BS-PAPA) with a fixed zero attractor is proposed in this paper. The proposed algorithm is obtained by integrating a weighted l 0 -norm penalty into the cost function of the BS-PAPA. Adding the penalty results in zero attraction terms in the weight update recursive equation of the BS-PAPA, which helps in the shrinkage of inactive coefficients. The proposed algorithm is named l 0 -block-sparse proportionate affine projection algorithm ( l 0 -BS-PAPA). The convergence analysis in the mean is derived for the l 0 -BS-PAPA. Secondly, for applications having time varying measurement noise, an adaptive zero attractor l 0 -BS-PAPA is also developed by adaptive optimisation of the zero attractor. This one is more robust to the varying degree of measurement noise than the former. A variable step-size l 0 -BS-PAPA is also introduced to further enhance the performance of the l 0 -BS-PAPA. Computer simulation experiments reveal that the l 0 -BS-PAPA outperforms the existing algorithms in block-sparse systems in terms of convergence rate, normalised misalignment, and tracking ability. [ABSTRACT FROM AUTHOR]

Flexibility is critical to the braided stent in curing vascular diseases, but there is no theoretical method to characterize its bending stiffness. In this paper, firstly based on the theory of mechanical spring, derivations of an explicit theoretical formula are made to calculate the bending stiffness of the braided stent. The formula does ignore the change of the braiding angle, which, according to a geometric analysis, can get neutralized and has rare effects on the result. Next, an experiment on a braided tube and numerical simulations on stents are conducted, which provide validations to the theoretical formula through comparisons of bending stiffness, stress distributions, and bending angle versus moment curves. Finally, a parametric analysis based on the formula is carried out. It finds that bending stiffness is mostly affected by the wire diameter, but a smaller braiding angle is the key to improving the bending flexibility while keeping a sufficient radial stiffness. It also finds that the formula is applicable to other braiding configurations, such as dual-layer and regular braiding stents. The formula provides theoretical foundations for the stiffness design of the braided stent and can simplify the design process. [ABSTRACT FROM AUTHOR]

A ring mesh is a large-scale manufacturable structure with versatile applications in architecture and for protective systems. However, the static and dynamic numerical simulation of a large-scale ring mesh is a resource-intensive task due to the many nonlinear contact points between the individual rings. To characterize the rigid body behavior of the ring mesh, in this paper, a representative volume element is loaded under different in-plane directions. The Green-Lagrangian strain tensor components are obtained as a result. An implicit one-step algorithm is used for this dynamic relaxation issue, modified by the use of stiff springs. Static convergence positions of a representative volume element are determined in several multiaxial tensile directions. The obtained deformation parameters can be used to simulate large deformations of large-scaled ring meshes. [ABSTRACT FROM AUTHOR]

When welding high-strength steel and ultra-thin plates, traditional resistance spot welding has technical problems such as a narrow process window and difficulty in ensuring both welding strength and forming quality, making it one of the bottlenecks in the manufacture of high-end structural parts in the fields of vehicles, aviation, and aerospace. The core reason is that the traditional spot welding thermal cycle mode is single, the energy is highly concentrated, and the controllability is poor. Therefore, there is an inconsistency between its energy distribution and nugget quality. In view of the above difficulties, a new idea of resistance spot welding of special-shaped electrodes based on energy distribution design is proposed. By inlaying insulating ceramics and other materials on the electrode end face, a "composite annular electrode" is prepared to realize the regulation of energy distribution in the welding process. In this paper, experimental and numerical simulation are carried out to reveal the detailed influence of the diameter of the ceramic core on the joint forming and thermal distribution. The results show that the welding effect of composite annular electrodes is better than that of traditional electrodes under different thickness plates. The maximum strength of the joint can reach 2600 N. The maximum temperature during welding shall not exceed 1930 °C. And the optimal ceramic core diameter is optimized for ultra-thin plates and high-strength steel plates commonly used in automobiles. [ABSTRACT FROM AUTHOR]

In this paper, an estimator for underwater DOA estimation is proposed by using a cross-linear nested array with an arbitrary cross-angle. The estimator removes the acoustic velocity factor by deriving the geometric relation of the cross-linear array. Compared with conventional DOA estimation algorithms via a linear array, this estimator eliminates systematic errors caused by the uncertainty factor of the acoustic velocity in the underwater environment. In comparison with the conventional acoustic velocity-independent algorithm, this estimator uses the nested array and does not have to estimate the value of the acoustic velocity, which improves the performance of DOA estimation. Moreover, the proposed method is only slightly inferior to some of the conventional algorithms if the acoustic velocity is estimated accurately. Numerical simulations are provided to validate the analytical derivations and corroborate the improved performance in underwater environments where the actual acoustic velocity is not accurate. [ABSTRACT FROM AUTHOR]

In this paper, the complex dynamical networks (CDNs) with dynamic connections are regarded as an interconnected systems composed of intercoupling links' subsystem (LS) and nodes' subsystem (NS). Different from the previous researches on structural balance control of CDNs, the directed CDNs' structural balance problem is solved. Considering the state of links cannot be measured accurately in practice, we can control the nodes' state and enforce the weights of links to satisfy the conditions of structural balance via effective coupling. To achieve this aim, a coupling strategy between a predetermined matrix of the structural balance and a reference tracking target of NS is established by the correlative control method. Here, the controller in NS is used to track the reference tracking target, and indirectly let LS track the predetermined matrix and reach a structural balance by the effective coupling for directed and undirected networks. Finally, numerical simulations are presented to verify the theoretical results. [ABSTRACT FROM AUTHOR]

In this paper, the fluid dynamics software Fluent is used to simulate the gas–liquid two-phase flow characteristics of a bottom-blown furnace under four different scale-up criteria. The results show that most of the low-velocity regions are located on both sides of the bubble flow region, and the bubble flow continuously swings upward in a zigzag motion, which leads to macroscopic instability. Under different scale-up criteria, the increase of gas velocity cannot effectively increase the velocity of the low-velocity zone in the molten pool, but can reduce the area of the low-velocity zone. Under each criterion, more than 95% of the area is in the velocity range of 0–6.4 m/s. High shear stress mainly exists at both walls and near the center of the bottom oxygen lance. Considering the gas flow consumption, velocity distribution, and shear-stress distribution, the modified Froude number is more suitable as the scale-up criterion. [ABSTRACT FROM AUTHOR]

Laser direct energy deposition (L-DED) can improve the forming efficiency of parts by controlling laser power, scanning speed, powder flow rate, and spot size. It is a good way to complete the processing and repair of complex parts. In this paper, a three-dimensional numerical model is established to study the dynamic cladding process (pool geometry, energy transfer, and dynamic solidification) of Inconel718 alloy during direct energy deposition. The fluid of volume (VOF) method is used to track the free surface of the melt pool, and the powder source model is established by discrete method. The results show that the molten pool size (area, width, height, depth) of the model is relatively uniform and can predict the shape of the molten pool well. The energy transfer in the molten pool is disturbed to some extent by the metal powder flow. The temperature gradient and cooling rate of the cladding layer are relatively large near the mushy area during the solidification process. [ABSTRACT FROM AUTHOR]

In this paper, we study consensus behavior based on the local application of the majority consensus algorithm (a generalization of the majority rule) over four-connected bi-dimensional networks. In this context, we characterize theoretically every four-vicinity network in its capacity to reach consensus (every individual at the same opinion) for any initial configuration of binary opinions. Theoretically, we determine all regular grids with four neighbors in which consensus is reached and in which ones not. In addition, in those instances in which consensus is not reached, we characterize statistically the proportion of configurations that reach spurious fixed points from an ensemble of random initial configurations. Using numerical simulations, we also analyze two observables of the system to characterize the algorithm: (1) the quality of the achieved consensus, that is if it respects the initial majority of the network; and (2) the consensus time, measured as the average amount of steps to reach convergence. [ABSTRACT FROM AUTHOR]

Spray ignition is widely encountered in energy and power engineering and is an important characteristic in combustor operation and design. Droplet ignition is an important part of spray ignition. Most present studies of droplet and spray ignition use numerical simulation, which sometimes cannot explicitly indicate the mechanism of ignition and is inconvenient for engineering applications. This paper reports experimental and analytical studies on ignition of a single droplet and spray under different flow conditions. Analytical results based on a one-dimensional model are compared with experimental results. The results reveal that the droplet ignition temperature decreases with an increase in the droplet size and increases with an increase in the relative gas velocity. The temperature of kerosene spray ignition by propane combustion products increases with an increase in the excess air and decreases with an increase in the droplet size. The obtained research results are useful for liquid-fueled combustor design and operation. [ABSTRACT FROM AUTHOR]

This paper considers mechanical systems with linear velocity forces and highly non-linear positional forces containing distributed-delay terms. Asymptotic stability conditions of system equilibria are proved using Lyapunov's direct method and the decomposition method. The developed approaches are applied to the monoaxial stabilization of a solid body. The theoretical outcomes are confirmed by computer simulation results. [ABSTRACT FROM AUTHOR]

The main purpose of this paper is the numerical analysis of a class of mathematical models that describe the contact between a thermo-piezoelectric body and a conductive foundation. Under the assumption of a static process, the material's behavior is modeled with a linear thermo-electro-elastic constitutive law and the frictional contact with Signorini's and Tresca's laws. A variational problem is derived and the existence of a unique weak solution is proved by combining arguments from the theory of variational inequalities with linear strongly monotone Lipschitz continuous operators. A successive iteration technique to linearize the problem by transforming it into an incremental recursive form is proposed, and its convergence is established. An Augmented Lagrangian variant, known as the Alternating Direction Multiplier Method (ADMM), is employed to split the original problem into two subproblems, resolve them sequentially, as well as update the dual variables at each iteration. To illustrate the performance of the proposed approach, several numerical simulations on two-dimensional test problems are carried out. [ABSTRACT FROM AUTHOR]

Hydraulic fracturing is a popular method used in the petroleum industry to increase the well performance by improving the permeability of the reservoir. However, while there has been extensive research on the development of the length of the fracture, the fractured height has been frequently assumed to be equal to the reservoir thickness. The objective of this paper is to study the influence of formation rock characteristics and the impact of underground stress state on the development of the fracture height. To achieve this objective, a finite element model was built using a cohesive zone method to predict the development of fracture height in time and space. Different scenarios were then effectuated by varying the values of the primary formation variables which are the Young's modulus, the porosity, the Poisson ratio, the fracture energy, and the maximum horizontal stress of the reservoir and of the beddings. This research therefore covered principally uncontrolled factors which are the formation properties and stress state underground, which contribute mostly to the erroneous prediction in fracture height. The findings revealed that the fracture height was strongly influenced by the properties of the formation and of the adjacent layers. However, the influence levels are not the same for different kinds of properties. This study showed that the most influential mechanical property of the rock on the fracture height is the Young's modulus. Regarding the porosity, its effect on the fracture height is extremely small. However, it is worth noting that the porosity is still an important parameter in hydraulic fracturing because it can be used to estimate others parameters and to model the development of fracture geometry which are width, length, and height. Practical suggestions for real-life hydraulic fracturing jobs can be deduced from this study, in order to control the fracture height as accurately as possible, and to decrease financial cost by concentrating mostly on the high influential factors instead of doing all kinds of tests for other less influential mechanical properties of the rock. [ABSTRACT FROM AUTHOR]

An electromagnetic flow sensor applied to the flow measurement of iron ore pipeline transportation will incur a measurement error after being used for a period of time, and the error will increase continuously. In this paper, based on the weight function theory of electromagnetic flow sensors, the main cause of the error is proposed. Specifically, in the process of using the electromagnetic flow meter the insulation lining of the sensor is easily damaged because the measuring pipe of the sensor constantly collides with the solid phase of the fluid, leading to a change in the distribution of the weight function of the electromagnetic flow sensor, which, in turn, changes the contribution of the induced electromotive force generated by each medium in the pipe to the measuring electrode. This paper is based on the PDE computer numerical calculation method, and, according to the analysis of the weight function under different boundary conditions, the rule that the output signal of the electromagnetic flow sensor decreases with increasing insulation lining area is obtained. The computer numerical calculation method used in this paper can provide a new approach to the theoretical analysis of the weight function of electromagnetic flow sensors. Furthermore, the conclusion reached in this paper can provide a theoretical basis for the development and maintenance of electromagnetic flow sensors applied to the flow measurement of iron ore pipelines. [ABSTRACT FROM AUTHOR]

Water injection wells often develop casing leaks that result in crossflow between two formations. The crossflow can be upward or downward depending on the respective location of each formation and the gravitation hydrostatic column between the formations. Traditionally, crossflow rates are measured by running production logs (flowmeter); a process that require well intervention. Such intervention in a well with compromised downhole integrity is not preferred as it incur additional cost and exposes the oilfield operator to possible mechanical risks such as stuck tools. In this work, we present a numerical method to predict crossflow rates without such intervention. The method requires readily available input from the water injection that includes injection flow rates and pressures, in addition, to shut-in well data. The workflow developed in this study includes nodal analysis and well performance modeling. A water injection well (Well-XYZ) was selected to validate the developed workflow as a case study in this paper. Well-XYZ has an upward crossflow that resulted from a downhole leak. The numerical method starts with building a well performance model before the leak develops. The injection data (pressure and flow rates) before leak development are used for this model. Second, a well with the same physical dimensions of Well-XYZ is imagined and modeled as a producing well from the downhole formation to the leak point. The shut-in well data of Well-XYZ are used to build the production well model. Third, we choose the leak point as the system node and obtain its pressure either by direct measurement or through calculation. Once the system node pressure is obtained, it is inputted as the wellhead producing pressure of the imagined well and its production rate will be the crossflow rate. The results of this method were tested by running a production log on Well-XYZ. The results of the production log showed that the method was able to accurately predict the crossflow rate with a less than 2% error. [ABSTRACT FROM AUTHOR]

This paper addresses the problem of speech quality enhancement by adaptive two-channel filtering algorithms. Recently, the forward blind source separation structure has been proposed and combined with normalized least-mean-square algorithm (FNLMS). The main drawback of two-channel FNLMS algorithm is its poor performance in steady state regime when the fixed step-sizes values are selected large. However, the slow convergence rate is observed with the small fixed step-size values. In this paper, we propose three new combinations of the basic FNLMS algorithm with simple variable step-sizes approaches, for improving both the steady state values and convergence rate (noted TVSF for Two-channel Variable Step-size Forward). In these modifications, we propose new configuration of two-channel forward structure by three simple and efficient variable step-sizes estimations. To confirm the good performance of three proposed TVSF algorithms compared with the classical fixed-step-size version, we have carried out several simulations in very noisy situations using several criteria. [ABSTRACT FROM AUTHOR]

The problem of taking into account the influence of turbulence comes up while solving both fundamental questions of geo- and astrophysics and applied problems arising in the development of new engineering solutions. Difficulties in applying the standard propositions of the theory appear when considering flows with a special spatial structure, for example, helical flows. The flow helicity determines the topology of vortices and is conserved in the process of energy transfer in a turbulent flow. In this paper we suggest an approach for numerical simulation of homogeneous isotropic helical turbulence aimed at detecting characteristic signatures of the inertial range and finding the distributions of the spectral energy and helicity densities. In this approach we use the TARANG code designed to numerically solve various problems of fluid dynamics in the regime of a developed turbulent flow and to study hydrodynamic instability phenomena of a different physical nature (thermal convection, advection of passive and active scalars, magnetohydrodynamics, and the influence of Coriolis forces). TARANG is an open source code written in the object-oriented C++ language with a high efficiency of computation on multiprocessor computers. Particular attention in the paper is given to the application of the tool kit from the package to analyze the solutions obtained. The spectral distributions and fluxes of energy and helicity have been computed for Reynolds numbers of 5700 and 14 000 on 5123 and 10243 grids, respectively. We have checked whether the -5/3 spectral law is realizable and estimated the universal Kolmogorov and Batchelor constants in the inertial range. An analysis of the energy and helicity transfer functions between the selected scales (shell-to-shell transfer) shows a significant contribution of nonlocal interactions to the cascade process. [ABSTRACT FROM AUTHOR]

This paper is concerned with a class of neutral-type neural networks with discontinuous activations and time-varying delays. Under the concept of Filippov solution, by applying the differential inclusions and the topological degree theory in set-valued analysis, we employ a novel argument to establish new results on the existence of the periodic solutions for the considered neural networks. After that, we derive some criteria on the uniqueness, global exponential stability of the considered neural networks and convergence of the corresponding autonomous case of the considered neural networks, in terms of nonsmooth analysis theory with Lyapunov-like approach. Without assuming the boundedness (or the growth condition) and monotonicity of the discontinuous neuron activation functions, the results obtained can also be valid. Our results extend previous works on the neutral-type neural networks to the discontinuous cases, some related results in the literature can be enriched and extended. Finally, two typical examples and the corresponding numerical simulations are provided to show the effectiveness and flexibility of the results derived in this paper. [ABSTRACT FROM AUTHOR]

In this paper, an uncertain SIR (spreader, ignorant, stifler) rumor spreading model driven by one Liu process is formulated to investigate the influence of perturbation in the transmission mechanism of rumor spreading. The deduced process of the uncertain SIR rumor spreading model is presented. Then an existence and uniqueness theorem concerning the solution is proved. Moreover, the stability of uncertain SIR rumor spreading differential equation is proved. In addition, the influence of different parameters on rumor spreading is analyzed through numerical simulation. This paper also presents a paradox of stochastic SIR rumor spreading model. [ABSTRACT FROM AUTHOR]

The partially linear varying coefficient spatial autoregressive model is a semi-parametric spatial autoregressive model in which the coefficients of some explanatory variables are variable, while the coefficients of the remaining explanatory variables are constant. For the nonparametric part, a local linear smoothing method is used to estimate the vector of coefficient functions in the model, and, to investigate its variable selection problem, this paper proposes a penalized robust regression estimation based on exponential squared loss, which can estimate the parameters while selecting important explanatory variables. A unique solution algorithm is composed using the block coordinate descent (BCD) algorithm and the concave-convex process (CCCP). Robustness of the proposed variable selection method is demonstrated by numerical simulations and illustrated by some housing data from Airbnb. [ABSTRACT FROM AUTHOR]

3D Concrete Printing (3DCP) is a rapidly evolving technology that allows for the efficient and accurate construction of complex concrete objects. In this paper, a numerical modelling approach is presented for the simulation of the printing process of cementitious materials, based on the homogeneous fluid assumption. To cope with the large deformations of the domain and the nonlinearity resulting from the use of a non-Newtonian rheological law, the Navier–Stokes equations are solved in the framework of the Particle Finite Element Method (PFEM). Furthermore, tailored solutions have been formulated and implemented for the time-dependent moving boundary conditions at the nozzle outlet and for the efficient handling of the inter-layer contact in the same PFEM framework. The overall computational cost is decreased by the implementation of an adaptive de-refinement technique, which drastically reduces the number of degrees of freedom in time. The proposed modelling approach is finally validated by simulating the printing process of six rectilinear layers and one multi-layer "wall". The results show good agreement with the experimental data and provide valuable insights into the printing process, paving the way for the use of numerical modelling tools for the optimization of materials and processes in the field of 3D Concrete Printing. [ABSTRACT FROM AUTHOR]

Transformerless grid-connected inverters for photovoltaic (PV) applications provide several advantages such as reduced cost and volume as well as an increased efficiency. However, the removal of the transformer gives rise to several problems related to leakage currents and electromagnetic interferences (EMI). This paper presents different chaotic unipolar sine-pulse width modulation (C-USPWM) techniques for a transformerless grid-connected PV inverter based on parameter selection. The main objective behind this proposed chaotic modulation technique is to reduce the conducted EMI without worsening the power quality and the common-mode voltage (CMV). The method is validated through numerical simulations and experimental tests carried out on laboratory prototype of an optimized H5 inverter (oH5). The obtained results showed its superiority to the conventional unipolar sine-pulse width modulation (USPWM). We showed also that the appropriate parameter selection of the C-UPSWM could advantageously combine an improved EMI performance and an efficient control, making it possible to deliver a significant reduction of the peaks' amplitudes in the frequency spectrum of the common-mode (CM) voltage. [ABSTRACT FROM AUTHOR]

Centrality is a numerical measure that characterizes the structural properties of a graph. In the presented work, centrality is used to analyze the load of the graph of urban roads in the city of Petrozavodsk. In the paper, we describe the method used to construct the road graph, present a modified centrality measure that takes into account the features of the transport network and the distribution of passenger traffic, and demonstrate the results of numerical simulations. For the transport graph, betweenness centralities were calculated with and without regard to the distribution of passenger traffic; a connectivity analysis was performed to identify critical, overloaded and reserve roads, and the routes that make the greatest contribution to the centrality of the most loaded roads. The results show that centrality can be used for the analysis of the structural features of the graph of urban roads, modeling sustainability and planning the development of the transport network. [ABSTRACT FROM AUTHOR]

In this paper, we propose an approach for describing wave propagation in finite-size microstructured metamaterials using a reduced relaxed micromorphic model. This method introduces an additional kinematic field with respect to the classical Cauchy continua, allowing to capture the effects of the underlying microstructure with a homogeneous model. We show that the reduced relaxed micromorphic model is not only effective for studying infinite-size metamaterials, but also efficient for numerical simulations and analysis on specimens of finite size. This makes it an essential tool for designing and optimizing metamaterials structures with specific wave propagation properties. The proposed model's efficiency is assessed through numerical simulations for finite-size benchmark problems, and shows a good agreement for a wide range of frequencies. The possibility of producing the same macroscopic metamaterial with different but equivalent unit cell "cuts" is also analyzed, showing that, even close to the boundary, the reduced relaxed micromorphic model is capable of giving accurate responses for the considered loading and boundary conditions. [ABSTRACT FROM AUTHOR]

In this paper, a novel locking-free finite beam element is proposed utilizing the absolute nodal coordinate formulation. By incorporating a gradient vector along the transverse direction at the boundary points, the linear interpolation of the gradient vector field within this element is achieved. Consequently, the problem of constant transverse strain distribution, which is observed in the Omar–Shabana beam element, is effectively addressed. Building upon this concept, this study further extends the proposed element from two dimensions to three dimensions. Additionally, it analyzes and compares the locking alleviation mechanism of the newly developed element and Patel–Shabana beam element. The analysis aims to provide insights into the factors contributing to the locking alleviation of different absolute nodal coordinate formulation (ANCF) elements. Furthermore, to demonstrate the effectiveness of the new element, six numerical simulation examples are designed, comprising three and three dynamic examples. These examples encompass small deformation statics, large deformation statics, small-scale motion, large-scale motion, and rotational motion problems. Finally, the results indicate that the proposed ANCF beam element can effectively alleviate the locking problem. The element exhibits robust adaptability, rationality, and effectiveness when subjected to complex mechanical characteristics by comparing the numerical results of this element with the classical Omar–Shabana, high-order Shen, and Patel–Shabana elements. [ABSTRACT FROM AUTHOR]

The capabilities of the numerical simulation of technological processes are limited by the accuracy and efficiency of determining the properties of materials continuously changing under repeated heating and cooling. The parameters of structural transformations are the principal factors affecting the properties of alloyed steels. In this paper, we present a method for determining the parameters of relationships describing C-shaped curves in the experimental diagrams of isothermal decomposition of austenite. The proposed approach makes it possible to reconstruct the entire C-shaped curve using a relatively small fragment near the "nose" (based on three points). The joint processing of a series of curves provides determining the parameters of ferritic, pearlitic and bainitic transformation kinetics. However, one should take into account the distinctive features of the diffusion decomposition of austenite. For example, ferrite and pearlite are formed in overlapping temperature ranges and have similar mechanical properties, but their combining into a single ferrite-pearlitic structure complicates the construction of a mathematical model for the transformation. The bainitic transformation is a transient one between diffusion and diffusionless transformations. In a part of the transformation temperature range the limit of conversion level is a function of temperature (just as in the case of martensitic transformation). It has been shown that, for the case of ferrite-pearlitic transformation, the best results can be obtained with the use of Kolmogorov–Avrami equation, whereas for the case of bainitic transformation, the best results can be obtained with the use of Austin–Rickett equation modified to take into account an incomplete conversion level of the transformation. [ABSTRACT FROM AUTHOR]

For realizing the precision dressing of worm grinding wheel of face gear, this paper studies the over-cutting phenomenon of worm grinding wheel in forming dressing and puts forward the solution. Combined with the forming principle of face gear worm and forming dressing method, the influence of the continuous dressing method on the grinding wheel helix and the relative position between the dresser and the worm are expounded. Based on the numerical simulation model and the actual machining phenomenon, two kinds of over-cutting phenomenon are discovered. To ensure the surface integrity of grinding wheel in continuous processing, the reasons and laws of over-cutting are deeply analyzed. The first kind of over-cutting can be eliminated by increasing the angle between the extended line and the axis on the dresser, and a method of estimating the minimum angle is proposed for a more reasonable design of the dresser. The second kind of over-cutting can be eliminated by choosing proper dressing interval while ensuring the utilization efficiency of worm, and the selection criteria of dressing interval in continuous dressing are put forward. To verify the proposed methods, digital model, Vericut, and SolidWorks are applied, and the results show that the proposed method can effectively solve the over-cutting problem. [ABSTRACT FROM AUTHOR]

Simple analytic formulas are obtained for the equatorial radius and relative rotation velocity of a star as functions of its absolute and relative angular momentum as a Huygens-Roche figure. The results are compared with numerical simulations of the structure of rotating stars and it is shown that the analytic model considered here is sufficient for describing the corresponding parameters. [ABSTRACT FROM AUTHOR]

This paper presents results of computer simulation experiments based on density functional calculations of the atomic structure and electronic spectrum of (n = 15–17) clusters. Based on the Wade–Mingos rules, we identify general trends in the formation of monoanionic hafnium-doped Sn clusters, which make it possible to optimize prognostic studies concerned with a search for novel nanostructured materials. We compare calculation results obtained with the B3LYP, B3PW91, and PBE functionals in combination with the SDD basis set and analyze the effect of the functionals on atomic structure optimization results. An optimal strategy is proposed for computer simulation experiments dealing with modeling of the spatial structure of Sn-based clusters and confirmed by comparison with available experimental data. [ABSTRACT FROM AUTHOR]

With the recent need to decrease energy use and promote indoor thermal comfort in overheating conditions, attention has been drawn to the passive cooling function of courtyards. This paper aims to determine the effect of proportions and orientations of courtyards on the indoor thermal performance of traditional houses in a warm, humid region so that this could guide further improvement and reinterpretation of this building type. The results of this parametric study were obtained through computer simulations of different cases with the aim to determine the influence of orientation, courtyard size and proportions on the indoor thermal energy balance and thermal comfort of a traditional building in a warm-humid region. Rather than promote passive cooling in the building, the findings suggest that the courtyard greatly increases solar heat gain, raising the temperature during the day. Higher solar heat gains and ventilation rates were observed in the courtyard cases with greater width and length. Nevertheless, this does not cause important differences in the average operative temperature of the entire building between the cases. As for orientation, lower heat gains were obtained in courtyards with the long axis-oriented east to west. Regardless of the cases, the study finally emphasizes the importance of the inhabitants controlling the opening of windows in the enclosed rooms since this could decrease the temperature by 1.1 °C from night to the early morning (23.00 hrs to 11.00hrs) and thus influence its thermal comfort. Conversely, opening the windows outside that time-lapse could cause an increase in temperature and more hours above the upper comfort limit. [ABSTRACT FROM AUTHOR]