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This paper studies the aircraft air circulation system and proposes a new architecture of the aircraft air circulation system. Combined with the neural network algorithm, the numerical simulation results of turbine, compressor, and heat exchanger are fitted and predicted, and the accuracy of the simulation model is verified by comparing with the experimental results. Comparing and analyzing the booster, F-15, F-35, and the newly proposed air circulation system, the engine bleed air volume consumed by the system under different flight conditions is obtained. The results show that the newly proposed air circulation system can save up to 71.4% of the engine bleed air compared with the simple boost and 29.8% of the engine bleed air compared with the F-35. The new air circulation system proposed in this paper can effectively improve the energy utilization rate of the system and reduce the consumption of engine bleed air. [ABSTRACT FROM AUTHOR]

This paper aims to study the law of pressure behavior and the characteristics of mutual influence in the process of steeply inclined coal seam mining. Based on the geological and engineering conditions of the B8 coal seam in Nanshan coal mine, this paper explores the law of mine pressure behavior in the process of steeply inclined coal seam mining by means of theoretical analysis and FLAC3D numerical simulation. Based on this, this paper also examines the influence of the interaction range between coal seams, the reasonable setting size of the section coal pillar, and the mining distance of the working face on the return air roadway. The results suggest as follows: (1) With an increase in the coal seam dip angle, the difference in the abutment pressure plastic zone between upper and lower coal pillars increases, and when mining in steeply inclined coal seams, the stress concentration in the lower and upper part of the working face deviates to the roof and floor respectively, which is obviously different from that of gently inclined coal seams. (2) The vertical stress above the section coal pillar changes in three stages with an increase in the width of the coal pillar, and the width of the coal pillar in the second stage can be taken as the reasonable size of the width of the coal pillar. The numerical simulation results are consistent with the theoretical calculation results, which indicate the high reliability of this method in determining the reasonable coal pillar size. (3) With an increase in the mining distance in steeply inclined coal seams, the maximum pressure around the working face and above the return air roadway has gone through three stages. When the distance between the working face and the adjacent return air roadway is close, the pressure above the return air roadway increases sharply, and disturbance is stronger. [ABSTRACT FROM AUTHOR]

Finite element method is an important method to solve mathematical problems in engineering. Many mathematical equations are difficult to solve, but it becomes very simple after using the finite element method. In this paper, the finite element method is applied to the calculation of gravity anomaly. First, the variational equation of gravity anomaly calculation is established, and then the gravity anomaly value ten times the distance away from the anomaly body is used as the boundary condition. By comparing the gravity anomaly obtained by solving the stiffness matrix with the analytical solution, it can be found that the method in this paper has high accuracy. Finally, the model of Jinchuan copper nickel deposit is used for calculation, and the calculated gravity anomaly field is inverted with Growth3D. It can be found that the inversion result is very close to the model, which verifies the effectiveness of the algorithm in this paper. [ABSTRACT FROM AUTHOR]

In order to solve the flood discharge problem of both small- and medium-sized warping dams in the Loess Plateau, a stepped spillway scheme, based on an ecological bag, to achieve full-section water flow and energy dissipation has been proposed in this paper. The hydraulic and energy dissipation characteristics of a stepped spillway layout scheme were studied using 3D numerical simulation. As the height of the dams is low and the spillways are short, the research has shown that the traditional single-step layout scheme leads to a low overall energy dissipation rate due to the small amount of energy dissipated in the initial steps. As a result of this, this paper has put forward two kinds of step layout schemes such as the shunt type and the staggered type for the initial steps. Through analysis of the flow state, the pressure distribution, and the total energy dissipation rate, the results have shown that shunt type and staggered type with front step deformation produced an obvious mixing of the water flow, fewer negative pressure areas, and a higher energy dissipation rate. The optimal energy dissipation rate of the staggered type reached 87.75%, and the maximum energy dissipation rate was increased by 27.97%. [ABSTRACT FROM AUTHOR]

As the underground space is relatively closed compared to other buildings, the space is hardly connected to the outside world through entrances and exits, which makes it difficult to ventilate and exchange heat with the outside. In this case, it is easy to cause a large number of casualties when a fire breaks out. When the fire happens smoke will be discharged merely by the mechanical exhaust, and air system should work simultaneously to replenish the oxygen inside. By setting four-group models, the paper analyzes the strategies for smoke extraction and air makeup in the underground construction. The paper points out that when the fire happens in a smoke bay, the neighborhood smoke extraction fan should be opened and the air makeup system should not be located at the top to disturb the smoke layer. By comparing and analyzing the performance of the smoke extraction and air conditioning system, the casualties caused by the high temperature toxic smoke from the fire can be reduced as far as possible. [ABSTRACT FROM AUTHOR]

In order to solve coupled fractional differential-integral equations more effectively and to deal with the problem that the huge algebraic equations lead to considerable computational complexity and large data storage requirements in the calculation process, this paper approximates the function of the unknown solution based on the Chebyshev wavelet of the second kind and then combines the collocation method to solve the numerical solution of nonlinear fractional Fredholm integral-differential equations. By using the proposed method, the original problem can be reduced to a system of linear algebraic equations, which can be easily solved by some mathematical techniques. In addition, the convergence analysis of the system based on the second kind of Chebyshev wavelet is studied. Several numerical test problems are presented, and the absolute error values under different fractional orders are given, which proves the superiority and effectiveness of the proposed method. It provides support for improving the precision and reliability of the system. [ABSTRACT FROM AUTHOR]

Three-dimensional free bending is a new tube forming technology with continuous variable curvature. In order to improve the forming quality of tube, this paper studies the principle of three-dimensional free forming system and the numerical calculation of bending moment in detail, and it uses the finite element simulation to model the mechanism in the bending process. The simulation model is used to simulate the forming process of copper tube, and the influence of key process parameters on the forming process is analyzed,the shape of the inner cavity of the bending die and the gap between the tube and the bending die are studied, the distance between the bending die and the guide column is studied, the axial feed rate on the forming quality of tubular bending parts has also been studied. The optimum process parameters were determined by finite element simulation and analysis. [ABSTRACT FROM AUTHOR]

Top-tensioned riser (TTR) is one of the most frequently used pieces of equipment in offshore petroleum engineering. At present, the research of its vortex-induced vibration (VIV) is mainly focused on numerical simulation with few analytical approaches. In this paper, the nonlinear dynamic equation of VIV about TTR is developed by introducing the third-order variable lift coefficient hydrodynamic model. The amplitude-frequency response equation under 1:1 primary resonance excitation is deduced based on the single mode discrete results. The nonlinear dynamic responses characteristics of the TTR vibration under the excitation of vortex-induced resonance are discussed. Bifurcation theory is used to study the singularity of the analytical solution of the riser system. The hysteresis and solitary solutions from the results of singularity analysis are found. Such results can provide guidance for the design and optimization of riser structural parameters. [ABSTRACT FROM AUTHOR]

In this paper, fractional calculus is applied to establish a novel fractional-order ferroresonance model with fractional-order magnetizing inductance and capacitance. Some basic dynamic behaviors of this fractional-order ferroresonance system are investigated. And then, considering noncommensurate orders of inductance and capacitance and unknown parameters in an actual ferroresonance system, this paper presents a novel fractional-order adaptive backstepping control strategy for a class of noncommensurate fractional-order systems with multiple unknown parameters. The virtual control laws and parameter update laws are designed in each step. Thereafter, a novel fractional-order adaptive controller is designed in terms of the fractional Lyapunov stability theorem. The proposed control strategy requires only one control input and can force the output of the chaotic system to track the reference signal asymptotically. Finally, the proposed method is applied to a noncommensurate fractional-order ferroresonance system with multiple unknown parameters. Numerical simulation confirms the effectiveness of the proposed method. In addition, the proposed control strategy also applies to commensurate fractional-order systems with unknown parameters. [ABSTRACT FROM AUTHOR]

This paper introduces the chaotic fractional-order Sprott Q system and its dynamics. The double compound combination of eight fractional-order chaotic synchronizations was investigated. This kind of synchronization is considered a generalization of many types of synchronization given in the literature. The analytical formula of the control functions is developed and proven using the tracking control method. As we know the fractional derivatives of two multiple functions are very difficult to calculate, and the tracking control method is more suitable for this kind of synchronization. This technique's communication is more secure and reliable because there are more drive and response systems. To achieve the proposed synchronization, four driving and four response identical chaotic systems are used as an example. This scheme may be used in many applications such as secure communications and safe information. Using the proposed double compound-combination synchronization is an example given to encrypt a message. The analytical results were confirmed by numerical simulation, and we found good agreement. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the direction of arrival (DOA) estimation problem with unfolded coprime linear array (UCLA) and propose a low computational complexity signal-subspace fitting (SF) algorithm. SF algorithm is able to achieve excellent DOA estimation performance while it requires global angular search (GAS). Especially in the several source signals situation, expensive complexity cost causes. To decrease computational complexity, we propose an initialized based SF (ISF) algorithm, which involves the several one dimensional (1D) partial angular search (PAS) instead of the multidimensional GAS. Consequently, the complexity is significantly decreased. Due to the full utilization of the array aperture, the proposed method in UCLA can attain better performance than general CLA (GCLA). In addition, as the SF is attractive in practical application, the proposed ISF algorithm lowers the computational cost, while achieving almost approximate estimation performance as traditional SF and noise subspace fitting (NF). Moreover, numerical simulations are provided and verify the effectiveness and the superiority of the proposed algorithm for the UCLA. [ABSTRACT FROM AUTHOR]

In this study, the multi-point plastic forming of 2024-O aluminum alloy sheets is the research object, ultrasonic vibration-assisted forming is applied in the stamping process, a combination of ABAQUS/EXPLICITE numerical simulation and theory is used, and multi-point forming experiments are performed to verify the research. In the process of multi-point forming, the influence of ultrasonic vibration on the plastic deformation and springback of sheet metal has inspired a new idea and method for multi-point forming of sheet metal. This paper presents the following: the basic theory of multi-point stamping and ultrasonic vibration-assisted metal sheet plastic forming; a comparison of the material parameters of the multi-point stamping method with and without ultrasonic vibration; the influence of different times on the results; the changes in parameters such as stress and strain at different frequencies; and the effect of its springback. [ABSTRACT FROM AUTHOR]

Stability and energy efficiency are the main focuses in the bipedal robot field. In this paper, we apply a multiphase gait, which is different from the widely used two-phase gait, to improve the stability at the moment, when a biped robot transfers from the double support phase to the single support phase. Then, we create dynamic equations with contact forces in each phase using Lagrangian formulation. Furthermore, the direct collocation method is utilized to generate the optimal trajectory toward both stability and energy efficiency. Finally, the comparison between multiphase gait and two-phase gait is performed with numerical simulations. The results prove that multiphase gait increases the stability margin in the cost of slightly decreasing energy efficiency. Besides, both gaits show a similar human-like characteristic in hip height variation during walking. [ABSTRACT FROM AUTHOR]

This study explores the pile-soil interaction mechanism and the optimal use of antislide piles for slope reinforcement based on finite difference numerical modelling. The force and displacement principles of slopes and antislide piles are analysed. The influences of various factors are investigated, such as postpile filling parameters, pile embedding methods, and pile cross-sectional shapes. Numerical modelling is used to determine the optimal layouts of antislide piles for push and traction landslides. The findings indicate that the cohesive force of the fill has a greater influence on the piles and slope than the friction angle and is the primary control factor. Fully buried antislide piles provide a better antisliding effect than semiburied ones. With fully buried piles, the best controlling effect is obtained when the ratio of the length of the pile's free section to the height of the sliding body is approximately 4/5. Moreover, stepped-cross-section piles provide better slope reinforcement than those with rectangular, T-shaped, or trapezoidal cross-sections. In practical applications, end-bearing arches can be utilized as the primary control structures, with friction arches used for secondary control to improve the soil arching effect as much as possible, thereby enhancing the stability of the piles and slope. To control landslides of various thrust forms, antislide piles should be set in the active section, the core sliding section, or both, as required. This paper provides guidance for improving the design of antislide piles. [ABSTRACT FROM AUTHOR]

In this paper, a novel chaotic new three-dimensional system has been studied by Zhang et al. in 2012. In the system, there are three control parameters and three different nonlinear terms which governed equations. Zhang et al. studied elementary (preliminary) dynamic properties of the chaotic new three-dimensional system by means of bifurcation diagram, maximum Lyapunov exponent, phase portraits, dynamics behaviors by changing some parameters etc., using all possible theoretical analysis and numerical simulation. In this paper, we have demonstrated its complete synchronization. The proposed results are verified by numerical simulations. [ABSTRACT FROM AUTHOR]

In this paper, the mutual information between the received signals and the source in the coprime linear array is investigated. In Shannon's information theory, the mutual information is used to quantify the reduction in the priori uncertainty of the transmitted message. Similarly, the spatial information in the coprime array is the mutual information between direction of arrival (DOA), source amplitude, and received signals. Such information content is composed of two parts. The first part is DOA information, and the second one is scattering information. In a single source scenario, we derive the theoretical expression and its asymptotic upper bound of DOA information. The corresponding expression of scattering information is also formulated theoretically. Besides, the application of spatial information is discussed. We can obtain the optimal array configuration by maximizing the DOA information of the coprime array. Similarly, the information is also used to quantify the performance difference between the coprime array and uniform array. In addition, the entropy error is employed to evaluate the estimation performance based on spatial information. Numerical simulation of the information content confirms our theoretical analysis. The results in this paper have important guiding significance for the design of the coprime array in the actual environment. [ABSTRACT FROM AUTHOR]

In this paper, we establish a new fixed-time stability theorem, which provides a novel fixed-time stability criterion and a novel upper bound estimate formula for the settling time. Numerical simulations show that the upper bound estimate for the settling time in this paper is tighter than those given in the existing fixed-time stability theorems. By designing a simple feedback controller, the fixed-time synchronization of neural networks with discrete delay is investigated based on the fixed-time stability theorem established in this paper. A numerical example is included to validate the effectiveness of the obtained theoretical results. [ABSTRACT FROM AUTHOR]

One of the most popular statistical models is a low-order polynomial response surface model, i.e., a polynomial of first order or second order. These polynomials can be used for global metamodels in weakly nonlinear simulation to approximate their global tendency and local metamodels in response surface methodology (RSM), which has been studied in various applications in engineering design and analysis. The order of the selected polynomial determines the number of sampling points (input combinations) and the resulting accuracy (validity, adequacy). This paper derives a novel method to obtain an accurate high-order polynomial while requiring fewer sampling points. This method uses a two-stage procedure such that the second stage modifies the low-order polynomial estimated in the first stage; this second stage does not require new points. This paper evaluates the performance of the method numerically by using several test functions. These numerical results show that the proposed method can provide more accurate predictions than the traditional method. [ABSTRACT FROM AUTHOR]

This paper presents the Semifree Flight theory used in a civil air traffic control (ATC) system to improve the capability of the traditional Free Flight mode. The progressiveness and hidden defects of the “Free Flight” model in civil aviation are analysed, and the Semifree Flight ATC system mode is introduced. Moreover, this paper presents the collaborative route planning method, which is the most important method used in the Semifree Flight ATC system. This collaborative route planning method can plan routes for each aircraft (either in flight or just before achieving flight) in real time, and the routes can satisfy all the safety constraints. The final numerical simulations verify the correctness and practicability of the Semifree Flight theory and the collaborative route planning method. [ABSTRACT FROM AUTHOR]

This paper constructs a dynamic multiobjective location model; three objectives are considered: the first objective maximizes the total utility of relief supplies, the second objective minimizes the number of temporary facilities needed to operate, and the third objective maximizes the satisfaction for all demand points. We propose an improved NSGA-II to solve the optimization problem. The computational experiments are divided into two sections: In the first procedure, the numerical experiment is constructed by the classical functions ZDT1, ZDT2, and DTLZ2; the results show that the proposed algorithm generates the exact Pareto front, and the convergence and uniformity of the proposed algorithm are better than the NSGA-II and MOEA/D. In the second procedure, the simulation experiment is constructed by a case in emergency management; the results show that the proposed algorithm is more reasonable than the traditional algorithms NSGA-II and MOEA/D in terms of the three objectives. It is proved that the improved NSGA-II algorithm, which is proposed in this paper, has high precision application for the sudden disaster crisis and emergency management. [ABSTRACT FROM AUTHOR]

In order to better study the propagation law of tunnel blasting in mountain landforms, taking the excavation blasting project of the Yangliu tunnel along the Yinsong expressway in Guizhou as the research object, the propagation law of vibration waves to tunnel blasting under the mountain tunnel was analyzed based on the ABAQUS finite element software and compared with the field monitoring data. The results show the peak vibration velocity of numerical simulation. Generally, the simulation value is slightly larger than the field monitoring value, but the average error of closing speed is less than 25% and the maximum error is less than 45%. The component velocity of surface peak vibration under blasting to load is the largest in the vertical direction. The "cavity effect" formed by the side-passing tunnel wall has the most significant amplification effect on the peak vibration velocity in the X direction of the rock and soil above it, which is about 1.62∼1.85 times and the resultant velocity is enlarged by 1.27∼1.45 times. Blasting vibration waves spread to the surface in the form of spherical waves inside the mountain, causing the vibration center of the surface to move to the area with lower elevation. The "cavity effect" caused by the side-through tunnel and the shift of the surface diffusion center to the lower part together led to the peak velocity of the lower measuring point of the Yangliu tunnel being much higher than that of the higher measuring point. The research results of this paper have certain reference significance in controlling the influence of underground blasting vibration on residential buildings in mountain areas. [ABSTRACT FROM AUTHOR]

The traditional gait analysis is mainly used in the research of joint dynamics and electromyography, which is helpful to develop a medical feedback system. The system judges the leg injury by analyzing the patient's gait, so as to provide effective treatment. In order to study how computer technology can be more appropriately introduced into physical education, this paper puts forward a new design method of manikin. The application of some key implementation technologies of computer simulation of two-dimensional motion images of human body is conducive to the scientization of physical education teaching and training. The experiment analyzes the daily movement of human body. MEMS technology is a technology to obtain human inertial data by simulating human motion with one or more computers. By integrating the collected data, different characteristics can be obtained. Then, classify these feature processing algorithms, and finally, identify the actions performed by the human body. Finally, the advantages of this recognition method in recognition accuracy are verified. [ABSTRACT FROM AUTHOR]

Microelectromechanical system (MEMS)-based devices have gained attention recently due to their beneficial biomedical applications. MEMS-based devices like microneedles have set new trends in drug delivery, vaccination, skin, and eye treatment. Different materials like metals, sugars, polymers, and silicon have been used for fabrication. Various techniques have been used for their fabrication, including laser ablation, lithography, injection molding, and additive manufacturing. The tip diameter of different micron ranges has been achieved. The strength and stiffness of the microneedle's tip have always been important in fabricating microneedles so that it does not break on insertion. This research paper presents a comparison between silver (Ag) and copper (Cu) solid microneedles by performing numerical analysis using the fuzzy approach, structural simulation, and fabrication. Firstly, structural simulation has been performed in ANSYS software to test the strength of silver (Ag) and copper (Cu) microneedles separately. The purpose is to compare the stress effect and fracture limit of both microneedles. The results collected from the simulation provide valuable target and prediction facts to fabricate improved designs of the solid Ag and Cu microneedles. Then, fuzzy-based numerical analysis has been performed in MATLAB software for both microneedles separately. In this numerical analysis, the effect on the range of microneedle tip diameter and cone length has been observed by varying input voltage and time. Finally, fabrication has been performed using a novel economical technique such as electrochemical etching. Electrochemical etching is a very low-cost and clean room-free technique as compared to other techniques used for the fabrication of microneedles. The fabrication technique adopted in this work is the same for both silver and copper microneedles. The scanning electron microscopy (SEM) characterization has been performed for both fabricated microneedle tips. The tip of the fabricated solid Ag and Cu microneedle has been then coated with drugs using the dip-coating method. The coated solid Ag and Cu microneedle's tip has been then characterized again using SEM. The numerical results calculated from the fuzzy analysis have been then compared with fabrication results. The fuzzy analysis gives the simulated size of the microneedle's tip for 5.05 μm silver and 5.12 μm copper which have very close approximation with the experimental values from the SEM micrographs which also give the values of the cone length from 400 to 500 μm and the tip size from 5 to 6 μm for the time of 10–15 minutes, whose values were optimized by the fuzzy analysis. The results of this research provide valuable benchmark and prediction data to fabricate improved designs of the silver solid microneedles for drug delivery and other biomedical applications. [ABSTRACT FROM AUTHOR]

Precast technology is increasingly favoured by bridge engineers, and the seismic performance of precast bridge piers urgently needs to be addressed. Precast piers have a complex load-bearing mechanism, and their design method has not been clearly determined. Fibre plastic hinge theory can satisfactorily analyse the seismic performance of precast piers. In this study, the seismic performance of precast piers is analysed through numerical simulation of pier columns based on the pseudostatic testing of a set of existing precast piers and combined with fibre plastic hinge theory. The results show the following: With reasonable constructional measures, precast piers connected by grouted sleeves indeed have seismic performance similar to that of cast-in-place components. Finite-element programs can be employed to simulate the mechanical properties of steel rebars before yielding well but not those after yielding or under fatigue. When fibre plastic hinges are used for finite-element analysis, if the fibre cross-section is reasonably divided, the length of the plastic hinge has little influence on the results; otherwise, too densely distributed plastic hinges may lead to nonconvergence of the results in a later working condition. The plastic hinge method recommended in this paper, especially the sectional fibre-cross-section division method, can obtain the plastic hinge performance state, it can help save the test cost and make up for the shortage of test data. [ABSTRACT FROM AUTHOR]

In the B-F reserve model, it is a very critical step to estimate the claim means of the accident year. However, the traditional method uses the prior estimators of the claim means based on the personal experience of actuaries or historical data. This method inevitably carries the subjectivity of the actuary himself. In this paper, a stochastic B-F model is established, and a prior distribution is constructed for the claim means in the accident year. The idea of the credibility theory is used to derive the linear Bayesian estimators of claim means. Finally, the empirical Bayesian method is used to estimate the first two moments of the prior distribution, and the empirical Bayesian estimators of the claim means and the corresponding reserves are derived. The estimators obtained in this paper do not depend on the specific forms of the sample distribution and the prior distribution and can be used directly in practice. In the numerical simulation, our estimates are compared with the traditional B-F estimates and the chain ladder estimates. It is verified that the estimates given in this paper have small mean square error. [ABSTRACT FROM AUTHOR]

The paper investigates the dynamical behaviors of a two-species discrete predator-prey system with Crowley–Martin functional response incorporating prey refuge proportional to prey density. The existence of equilibrium points, stability of three fixed points, period-doubling bifurcation, Neimark–Sacker bifurcation, Marottos chaos, and Control Chaos are analyzed for the discrete-time domain. The time graphs, phase portraits, and bifurcation diagrams are obtained for different parameters of the model. Numerical simulations and graphics show that the discrete model exhibits rich dynamics, which also present that the system is a chaotic and complex one. This paper attempts to present a feedback control method which can stabilize chaotic orbits at an unstable equilibrium point. [ABSTRACT FROM AUTHOR]

This paper proposes and investigates a problem of preview tracking control for a class of continuous-time singular interconnected systems. Firstly, the related items are deleted to obtain several isolated subsystems with low dimensions. An error system is constructed for each isolated subsystem so that the tracking error is included in the state vector of the error system; then, the tracking problem is transformed into a regulation problem. Secondly, the preview tracking controller is designed for each error system and obtained controllers are combined as the controller of the error system of the singular interconnected system. Thirdly, the Lyapunov function method is utilized to determine the constraints of the related terms so that the closed-loop system of the error system of the singular interconnected system is stable under the action of the controller obtained. Finally, the preview tracking controller of the singular interconnected system is obtained from the relationship between the error system and the original system. A numerical simulation algorithm for continuous-time singular systems is also proposed in this paper. The numerical simulation illustrates the effectiveness of the theoretical results. [ABSTRACT FROM AUTHOR]

Time-delayed feedback control is commonly used on the vehicle semiactive suspension system to improve ride comfort and safety. However, its performance on the suppression of road random excitation is less significant than that on the suppression of simple harmonic excitation. Therefore, this paper proposes a strategy of time-delayed feedback control with the vertical displacement of wheel and the method of optimizing its parameters based on equivalent harmonic excitation. The optimal parameters of the time-delayed feedback control are obtained in this way for the vehicle semiactive suspension system in its effective frequency band. The results of numerical simulation verify that the time-delayed feedback control with vertical wheel displacement and its parameter optimization based on equivalent harmonic excitation can significantly improve the ride comfort and stability. Its performance is much better than that of the passive suspension system. [ABSTRACT FROM AUTHOR]

This paper proposes new mathematical models of representation, which can describe the dynamic behavior of large-scale nonlinear systems, such as an extended mathematical model of Volterra series, interconnected Hammerstein structures, and interconnected Wiener structures. In this research, we focus on the class of large-scale nonlinear systems, which are composed of several interconnected nonlinear subsystems. In this context, a discrete nonlinear mathematical model with unknown time-varying parameters, mono-variable, characterizes each interconnected subsystem operating in a deterministic or stochastic environment. An illustrative numerical simulation example of two interconnected nonlinear processes is provided to prove the validity and the performance of the developed theoretical results. [ABSTRACT FROM AUTHOR]

A reasonable selection of the pillar mining plan is the key to ensure smooth mining in the goaf group, which plays an important part in safe production. In formulating and optimizing the pillar mining plan, the influence of the ground pressure evolution law should be fully considered. This paper first introduces two mining plans for pillars, and then, numerical simulations were used to analyze the two mining plans from four perspectives such as stress evolution law, stress concentration degree, force state of pillars, and weak marble layers. The results show that the mining plan 1 that retreats from the middle of the ore body to the two wings is the optimal as it can realize sequential mining in high-stress concentration areas at the middle section. This effectively alleviates the stress on the surrounding rock during mining and will not aggravate the collapse of the marble-interbedded area. [ABSTRACT FROM AUTHOR]

In this paper, an unstable heat equation where the observation signal suffers from a given time delay has been considered. In order to remove the unstable boundary condition, the original system has been converted into the stabilizing system by backstepping transformation under which the form of the stabilizing controller can be obtained. For the sake of overcoming instability produced by the time delay, firstly, we construct the Luenberger observer and design the predictor. Then, the estimated output feedback controllers have been obtained based on the observer and predictor systems. It is shown that the closed-loop system is stable exponentially. At last, numerical simulations have been given to illustrate the effectiveness of the stabilizing output feedback controllers. [ABSTRACT FROM AUTHOR]

With the continuous development of economy, the traditional urban management system cannot meet the needs of the city. In order to solve many inconvenient urban problems brought by the traditional urban management system and provide convenience for urban development more quickly, the concept of "smart city" has been put forward and gradually applied to urban construction. Based on cloud computing and Internet of things, the service system and construction of smart city were studied in detail; on this basis, the demand of construction of smart city in coastal city A and the construction and practical application of smart city of city A in our country were analyzed so as to provide some reference value for the construction of smart city in our country. Through an in-depth test of the data mining algorithm, this paper verifies the calculation effect of the data mining algorithm and the optimization effect of a smart city public management system. [ABSTRACT FROM AUTHOR]

In this paper, the finite element analysis was firstly employed to investigate the thermal analysis on two fireproof sealing models with ANSYS software under HC standard temperature-time condition. The main thermal parameters were analyzed and obtained, including temperature field, thermal flux, and thermal gradient. After comparing the two fireproof sealing models, the major conclusions are summarized as follows: In terms of temperature field, the temperature on the left side of the first model ranges from 60 to 524°C in. In contrast, the highest temperature on the left side of the second model eventually reaches below 151°C. Moreover, the vectors of thermal gradient in the first model are compared with the second model, and the temperature gradient disturbance is more obvious in the second fireproof sealing model, which is better to slow down temperature spreading. The accelerated speed of E1 and G1 is 0.0096°C/s and 0.0619°C/s partly, which are far more than C2 and F2 with values of 0.0028°C/s and 0.0078°C/s, respectively. In a word, the performance of the first fireproof sealing model is inferior to the second fireproof sealing model. The conclusions of the study are meaningful to improve the thermodynamic performance of the fireproof sealing in the converter station. [ABSTRACT FROM AUTHOR]

This paper presents the attitude tracking of a class of satellite control systems under external disturbances. Once the error dynamics of the satellite are obtained, a nonlinear transformation expresses them in a suitable representation for the design of a high-gain observer and backstepping control. The observer-based backstepping controller is then designed to drive the angles of the satellite dynamics to their desired values in the presence of exogenous disturbances. Closed-loop stability of the proposed controller is demonstrated via Lyapunov theory, and its effectiveness is confirmed through numerical simulations. [ABSTRACT FROM AUTHOR]

The multiagent system has the advantages of simple structure, strong function, and cost saving, which has received wide attention from different fields. Consensus is the most basic problem in multiagent systems. In this paper, firstly, the problem of partial component consensus in the first-order linear discrete-time multiagent systems with the directed network topology is discussed. Via designing an appropriate pinning control protocol, the corresponding error system is analyzed by using the matrix theory and the partial stability theory. Secondly, a sufficient condition is given to realize partial component consensus in multiagent systems. Finally, the numerical simulations are given to illustrate the theoretical results. [ABSTRACT FROM AUTHOR]

In order to control pests and eventually maintain the number of pests below the economic threshold, in this paper, based on the nonsmooth dynamical system, a two-stage-structured pest control Filippov model is proposed. We take the total number of juvenile and adult pest population as the control index to determine whether or not to implement chemical control strategies. The sliding-mode domain and conditions for the existence of regular and virtual equilibria, pseudoequilibrium, boundary equilibria, and tangent points are given. Further, the sufficient condition of the locally asymptotic stability of pseudoequilibrium is obtained. By numerical simulations, the local bifurcations of the equilibria are discussed. Our results show that the total number of pest populations can be successfully controlled below the economic threshold by taking suitable threshold policy. [ABSTRACT FROM AUTHOR]

In this paper, the problem of robust preview control for uncertain discrete singular systems is considered. First of all, by employing the forward difference for uncertain discrete singular systems, the singular augmented error system with the state vector, the input control vector, and the previewable reference signal is derived. Since there is a singular matrix in the system, the existing method cannot be directly applied to this problem. By considering the stability of the transposition system with Linear Matrix Inequality (LMI) method, a new stability criterion for the transposition system is introduced. Then, the robust controller for the augmented error system is obtained, which is regarded as the robust preview controller for the original singular system. At last, the numerical simulation shows the correctness and effectiveness of the results. [ABSTRACT FROM AUTHOR]

In this paper, we study the H∞ control problem for Linear Parameter Varying (LPV) discrete systems with random time-varying network delay. The state matrices of LPV discrete systems are deterministic functions and changed with parameters; the range of parameters is measurable. Considering the characteristics of networks with random time-varying delay, we proposed a new parameter-dependent H∞ performance criterion based on the Lyapunov stability theory. The coupling between Lyapunov functions and system matrices could be eliminated by introducing an additional matrix in this criterion, which made it easier for numerical implementation. On this basis, we designed a state feedback controller by virtue of linear matrix inequalities, which transformed the sufficient conditions into existence condition of solution of parametric linear matrix inequalities. The designed controller could keep the closed-loop system asymptotically stable under given time delay and probability and meet predefined performance metric. The validity of the proposed method is verified by numerical simulation. [ABSTRACT FROM AUTHOR]

This paper studies bipartite consensus for first-order multiagent systems. To improve resource utilization, event-based protocols are considered for bipartite consensus. A new type of control gain is designed in the proposed protocols. By appropriate selection of control gains, the convergence rate of the closed-loop system can be adjusted. Firstly, for structural balance case, necessary and sufficient conditions are given on communication relations and consensus gains to achieve bipartite consensus. Secondly, for structural unbalance case, necessary and sufficient conditions are proposed to ensure the stabilizing of the system. It can be found that the system will not show Zeno behavior. Numerical simulations are used to demonstrate the theoretical results. [ABSTRACT FROM AUTHOR]

To reduce the chattering issue and improve the dynamic tracking performance of the speed regulation of the permanent magnet synchronous motor (PMSM) system, the sliding mode control (SMC) with an enhanced exponential reaching law (EERL) is proposed in this paper. Compared to the SMC with conventional reaching law (CRL), the proposed SMC based on the EERL makes the convergence rate be associated with the change of the system state variable. In order to implement the minimum resource utilization of the embedded processor while guaranteeing the performance of the system, the event triggered strategy is developed for SMC, which possesses the excellent robustness and saves the energy cost. The stability of the event triggered SMC control law is proved by the Lyapunov function and the minimum control execution time interval is also derived. Finally, the effectiveness of the proposed EERL and the satisfactory performance of the event triggered SMC are demonstrated by the simulation results. [ABSTRACT FROM AUTHOR]

Radar bias estimation is an important part of a multisensor tracking system. Because the radar bias models in current efforts are not sufficiently accurate, the bias estimation accuracy is not satisfied. First, a general radar bias model, in which the importance of the sensor-target pair-related bias is emphasized, is proposed in this paper. Moreover, the target-sensor pair-related bias is considered on the grounds of the impact of atmospheric refraction on the electromagnetic wave propagation path. Second, by using the augmented state vector with the target state and radar bias, a dynamic equation and measurement equation under the IMM framework are obtained. Last, the IMM-UKF estimator is utilized to obtain the target state and radar bias simultaneously. The numerical simulations show that the accuracy of the bias estimation together with the target states estimation can be improved via the proposed radar bias model. [ABSTRACT FROM AUTHOR]

Open source design (OSD) is an emerging cluster design mode based on Internet, and it takes full advantage of knowledge, technology, and resources among designers to promote product development. In this mode, designers’ behaviors of collaboration have important influence on product development process. In this paper, firstly collaboration flow including two types of collaboration relations between designers in open source design is depicted. Secondly, two-phase collaborative behavior model including partner selection and response is built by means of utility functions. At last, simulation experiment including 4 scenarios is designed based on open source project of mobile phone and conducted by multiagent simulation, and contrastive analysis is carried out to study collaboration behaviors’ impact on open source design process. The results show that the two-phase collaborative behavior model elaborately describes structure evolution of Open Source Community (OSC) as well as designers’ collaboration behaviors and that different ways of partner selection behaviors have significant impact on the evolution of OSD process as well as OSC structure. Furthermore, the results suggest that designers should better consider more the factor of matching degree between designers but less collaboration record. [ABSTRACT FROM AUTHOR]

Recently, the design of sparse linear array for direction of arrival (DOA) estimation of non-Gaussian signals has attracted considerable interest due to the fact that the fourth-order difference coarray offered by non-Gaussian significantly increases the aperture of a virtual linear array, which improves the performance of DOA estimation. In this paper, a super four-level nested array (S-FL-NA) configuration based on fourth-order cumulants (FOC) is proposed. The S-FL-NA consists of uniform linear arrays which have different interelement spacing. The proposed array configuration is designed based on interelement spacing, which, for a given number of sensors, is uniquely determined by a closed-form expression. We also derive the closed-form expression for the degrees of freedom (DOFs) of the proposed array. The optimal distribution of the number of sensors in each uniform linear array of the proposed array is given for an arbitrary number of sensors. Compared with the existing sparse arrays, the proposed array can provide a higher number of degrees of freedom and a larger physical array aperture. In addition, to improve the calculation speed of the fourth-order cumulant matrix, we simplify the FOC matrix by removing some redundancy. Numerical simulations are conducted to verify the superiority of the S-FL-NA over other sparse arrays. [ABSTRACT FROM AUTHOR]

Performance evaluation of trajectory tracking for a rotary flexible joint system is demonstrated in this paper. The robust and converse dynamic (RCD) technique is proposed and implemented for this evaluation. This control methodology is of the left inversion type, i.e., the control inputs are obtained by means of plant output error feedback. RCD control encompasses the baseline inverse (BI) control and sliding mode control-based discontinuous control element. The baseline inverse controller enforces the prescribed servo (virtual) constraints that represent the control objectives. The control objectives of the baseline inverse controller are enclosed in the form of servo (virtual) constraints which are inverted using Moore–Penrose Generalized Inverse (MPGI) to solve for the baseline control law. To boost the robust attributes against parametric uncertainties and disturbances, a discontinuous control function is augmented with baseline controller such that semiglobal practical stability is guaranteed in the sense of Lyapunov. To exhibit the effectiveness of RCD control in terms of tracking performance, computer simulations are conducted in Simulink/Matlab environment. Furthermore, the practical implementation is also investigated through a real-time experiment on Quanser's rotary flexible joint manipulator system. The experimental results obtained by RCD are compared to the conventional sliding mode and fractional-order control techniques. [ABSTRACT FROM AUTHOR]

This paper proposed a finite time convergence global sliding mode control scheme for the second-order multiple models control system. Firstly, the global sliding surface without reaching law for a single model control system is designed and the tracking error finite time convergence and global stability are proved. Secondly, we generalize the above scheme to the second-order multimodel control system and obtain the global sliding mode control law. Then, the convergent and stable performances of the closed-loop control system with multimodel controllers are proved. Finally, a simulation example shows that the proposed control scheme is more effective and useful compared with the traditional sliding mode control scheme. [ABSTRACT FROM AUTHOR]

The analysis of adaptors’ deformation and stress is an important prerequisite for the design of the adapters. This paper proposed the mathematical description and analytical method for the sponge cylinder and rubber cylinder under pressure. The analytical formulas on deformation and stress of interference fit between adapters and launchers are deduced. Also, the correctness of the analytical formula is verified by numerical simulation. Furthermore, the effect of precompression and the sponge’s thickness ratio on adapter’s deformation and stress is studied. The following results can be concluded: the results of numerical simulation are basically consistent with that of analytical formula. After installing the adapter into the launcher, the rubber layer will move inward as a whole, then the sponge layer and the rubber layer are subjected to radial and tangential compressive stress. When the precompression is smaller than 0.0075 or larger than 0.0015, the deformation and stress of adapter are approximately in proportion to precompression. If the precompression keeps constant, the deformation and stress of adapter will have extremum when the thickness ratio of sponge equals to a certain value. [ABSTRACT FROM AUTHOR]

We choose the delay as a variable parameter and investigate the Lorentz-like system with delayed feedback by using Hopf bifurcation theory and functional differential equations. The local stability of the positive equilibrium and the existence of Hopf bifurcations are obtained. After that the direction of Hopf bifurcation and stability of periodic solutions bifurcating from equilibrium is determined by using the normal form theory and center manifold theorem. In the end, some numerical simulations are employed to validate the theoretical analysis. The results show that the purpose of controlling chaos can be achieved by adjusting appropriate feedback effect strength and delay parameters. The applied delay feedback control method in this paper is general and can be applied to other nonlinear chaotic systems. [ABSTRACT FROM AUTHOR]

This paper presents an investigation of a cylinder with material attributes that vary arbitrarily in the radial direction under non-uniformly distributed normal and tangential pressures. A stress and displacement solution method for plane strain on a radial heterogeneous cylinder with inner and outer surfaces subjected to uneven normal and tangential pressures under two types of contact conditions (i.e., complete contact and smooth contact) is proposed based on the theory of elastic mechanics. In addition, a group of linear equations is derived, through which the analytical solution of a radial heterogeneous cylinder under a non-uniform load can be obtained. The validity of the analytical solution is verified by comparing it with the results of a numerical simulation. This research shows that the solution is more convenient and universal than traditional methods and can provide a theoretical basis for the stress state analysis, stability evaluation, and structure design of heterogeneous cylindrical structures, all of which have great significance in practical engineering. [ABSTRACT FROM AUTHOR]