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In order to strengthen the detection and monitoring of space targets, especially non-cooperative targets, more and more attention has been paid to the characteristics of space targets. The position, velocity, attitude, angular velocity and material complex refractive index of space target were inversely estimated by unscented Kalman filter (UKF). The observation angle, photometric and degree of polarization data were used as the observation values to estimate the state of the target. Based on the position and velocity kinematics model and the attitude and angular velocity dynamic model, the time evolution of the five states was completed, and the joint estimation of the five state parameters was realized. The simulation results show that setting reasonable initial state value, state equation and measurement equation noise, the errors of five state parameters can converge reasonably, and UKF can better predict the five characteristic parameters of space targets. At the same time, it is also verified that the observation angle, luminosity and polarization data can be used to retrieve the five indirect observation characteristic information of space moving targets. [ABSTRACT FROM AUTHOR]

In this paper, the new non-integer-order state space model of heat processes in a one-dimensional metallic rod is addressed. The fractional orders of derivatives along space and time are not exactly known, and they are described by intervals. The proposed model is the interval expanding of the state space fractional model of heat conduction and dissipation in a one-dimensional metallic rod. It is expected to better describe reality because the interval order of each real process is difficult to estimate. Using intervals enables describing the uncertainty. The presented interval model can be applied to the modeling of many real thermal processes in the industry and building. For example, it can describe the thermal conductivity of building walls. The one-dimensional approach can be applied because only the direction from inside to outside is important, and the heat distribution along the remaining directions is uniform. The paper describes the basic properties of the proposed model and supports the theory via simulations in MATLAB R2020b and experiments executed with the use of a real experimental laboratory system equipped with miniature temperature sensors and supervised by PLC and SCADA systems. The main results from the paper point out that the uncertainty of both fractional orders impacts the crucial properties of the model. The uncertainty of the derivative along the time affects only the dynamics, but the disturbance of the derivative along the length disturbs both the static and dynamic properties of the model. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

It is noted that, in the general case, diagrams of cyclic elastoplastic deformation of a material characterize its resistance to low-cycle loading and display the relationship between current stress values and deformation during deformation. Such diagrams in the mechanics of deformation and fracture are described by complex equations of state that depend nonlinearly on the conditions and loading modes, including temperatures, strain rates, cycle shapes, types of stress state, absolute dimensions of sections, types of working media, types of structural material, etc. The mentioned factors in their entire complex influence the shape of curves (diagrams) of material deformation and the main parameters of the equations of state describing them, for example, such basic characteristics of mechanical properties as the modulus of elasticity, yield stress and ultimate strength, and indicators of static and cyclic hardening. As exemplified by experimentally obtained data on the kinetics of cyclic and one-sided accumulated plastic deformations in each of the half-cycles (cycles) of loading during static and low-cycle tests of specimens from a heat-resistant nickel alloy, it is shown that, under conditions of cyclic elastoplastic deformation, these deformation characteristics have an essentially nonlinear pattern of change, which is described on the basis of power equations and the parameters of cyclic deformation diagrams included in them. Here, the parameters of these equations depend on the type of cyclically hardening, softening, or stable material during its deformation in the elastoplastic region. It is noted that the resistance to cyclic elastoplastic deformations of a material can be described by a set of analytical expressions with a kinetic function included in them, which varies over the number of loading half cycles, in the form of power or exponential expressions depending on the cyclic properties of the material and data on the characteristics of the mechanical properties of specific structural materials. The obtained computational and experimental data on the kinetics of deformations of the alloy under study during its cyclic elastoplastic loading and on the parameters of the deformation diagrams, which are the basic characteristics for the corresponding equations of state, make it possible to fully apply the deformation-kinetic criterion for the accumulation of damage under the considered loading conditions for calculating the durability of structural elements made from it, which are operated, as a rule, under complex temperature and power conditions. The results of the performed experiments and calculations are presented in the form of diagrams of the cycle-by-cycle kinetics of cyclic and accumulated plastic deformations of the studied material under soft and hard loading conditions and in a wide range of test temperatures. [ABSTRACT FROM AUTHOR]

In this paper, the new non-integer-order state space model of heat processes in a one-dimensional metallic rod is addressed. The fractional orders of derivatives along space and time are not exactly known, and they are described by intervals. The proposed model is the interval expanding of the state space fractional model of heat conduction and dissipation in a one-dimensional metallic rod. It is expected to better describe reality because the interval order of each real process is difficult to estimate. Using intervals enables describing the uncertainty. The presented interval model can be applied to the modeling of many real thermal processes in the industry and building. For example, it can describe the thermal conductivity of building walls. The one-dimensional approach can be applied because only the direction from inside to outside is important, and the heat distribution along the remaining directions is uniform. The paper describes the basic properties of the proposed model and supports the theory via simulations in MATLAB R2020b and experiments executed with the use of a real experimental laboratory system equipped with miniature temperature sensors and supervised by PLC and SCADA systems. The main results from the paper point out that the uncertainty of both fractional orders impacts the crucial properties of the model. The uncertainty of the derivative along the time affects only the dynamics, but the disturbance of the derivative along the length disturbs both the static and dynamic properties of the model.

Structural vibration includes both translational and rotational degrees of freedom, but the latter are often ignored. The paper establishes a dynamic inclination measurement model based on the existing accelerometer, and constructs state and measurement equations that comprehensively represent translational and rotational degrees of freedom. Then, the extended Kalman filtering method is used to linearize and discretize the state equation and measurement equation, and the filtering process of dynamic Inclination Identification is derived. The feasibility of the method was verified through an example of a simply supported beam structure. [ABSTRACT FROM AUTHOR]

Smart transformation and green development are the core research directions of electric vehicles. An electric tractor is powered by the vehicle battery. The motor converts electric energy into mechanical energy and drives the wheels through the drive train. Therefore, the electric tractor model is a modular mathematical model for the battery, motor, drive train, and drive wheel. A class of high-order terminal sliding mode control strategies is adopted to establish the relative rotational angles of drive wheels, driving angular speeds, and motor angular speeds as input, and driving angular speeds and motor angular speeds as output. This process ensures stable operating speed and good working quality under the operating conditions and achieves small-scale unattended driving. The output is a nonlinear system state equation. An n-order derivative continuous function is introduced to design the terminal sliding surface of the sliding mode. A control function to reduce chattering is also designed to ensure that the output function converges at the finite time and the existing sliding stage achieves zero steady-state error. Simulation results of the whole electric tractor model show that the speed remains stable under the condition of outside interference, and experiments verify the feasibility of the control strategy. [ABSTRACT FROM AUTHOR]

For a hydropower system with a relatively short tail tunnel and wide variation of tail water level, the ceiling-sloping tail tunnel (CSTT) is often recommended. Considering various flow patterns and traveling free-surface-pressurized interface in the CSTT, stability modeling and analysis of the governor-turbine-hydraulic system shows more challenging. Based on state equations analysis, an improved nonlinear model considering transition part, and a new linear model for downstream free-surface flow are derived. Further comparative analysis indicates that, by introducing these models, water flow characteristics in transition part have positive effect on operation stability with an around 4.0% increase of attenuation rate, while that of downstream free-surface flow has a negative effect with a 21.8% decrease rate on the absolute value of negative attenuation factor. For stability optimization of the CSTT, to properly increase its bottom width is preferable, herein with a 6.2% increase of attenuation rate for a 2.0 m increase of bottom width, while a reasonable ceiling slope should be optimized considering the counteraction effect of upstream pressurized flow and downstream free-surface flow. The new developed models and further discussion for the hydropower systems with a CSTT will greatly improve system's stability evaluation and advance the development of renewable energy. • A new nonlinear model considering the effect of flow transition part is developed. • A linear stability model for the downstream free-surface flow is derived. • Positive effect of water flow in transition part on operation stability is revealed. • Negative effect of downstream free-surface flow on operation stability is clarified. • Optimization criterion of the ceiling-sloping tail tunnel is presented. [ABSTRACT FROM AUTHOR]

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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

Petri nets (PNs) can model various event-driven systems well and detect a fault via reachability analysis. Some state-equation-based approaches are designed for only subclasses of PNs with specific structures. A key issue for PNs’ reachability analysis approach based on state equation is that a non-negative integer solution (NIS) to a state equation is necessary but not sufficient for a marking’s reachability. In this paper, we propose a circuit-based subnet. For ordinary Petri nets with token-free circuit-based subnets, we present an algorithm to determine that the state equation has NISs but the marking is non-reachable. We adopt a divide-and-conquer strategy to consider each circuit-based subnet. The proposed method is tested on a PN-based flexible manufacturing system with unreliable resources. When unreliable resources are lost, the non-reachable markings can be determined effectively. Besides, simulations are done, and the results verify the efficiency of the proposed algorithm compared with the reachability-tree-based method.

Following a recently considered generalisation of linear equations to unordereddata vectors and to ordered-data vectors, we perform a further generalisation to data vectors that are functions from k-element subsets of the unordered-data set to vectors of integer numbers. These generalised equations naturally appear in the analysis of vector addition systems (or Petri nets) extended so that each token carries a set of unordered data. We show that nonnegative-integer solvability of linear equations is in nondeterministic exponential time while integer solvability is in polynomial time. [ABSTRACT FROM AUTHOR]

The nonlinear state equations describing the coupling between control rod drop and fluid flow were proposed to solve the problem of control rod drop in nuclear reactors. The state equations have a uniform format for different fluid states in the process of control rod drop, which can conveniently deal with the problem for different working conditions. To efficiently analyze the falling process, accurately capture the sudden change of flow state and ensure the numerical stability of time integral, an adaptive time step-based symplecticity-preserving algorithm was proposed. Numerical examples show that, the proposed numerical model can accurately calculate the key data such as the displacement, the velocity, the acceleration and the falling time of the control rod in the falling process with a large time step, and the calculated results are in good agreement with those obtained the by the commercial software. [ABSTRACT FROM AUTHOR]

Abstract In this work, we have determined the mean square relative displacement, elastic constant, anharmonic effective potential, correlated function, local force constant, and other thermodynamic parameters of diamond-type structured crystals under high-pressure up to 14 GPa. The parameters are calculated through theoretical interatomic Morse potential parameters, by using the sublimation energy, the compressibility, and the lattice constant in the expanded X-ray absorption fine structure spectrum. Numerical results agree well with the experimental values and other theories.

Smart transformation and green development are the core research directions of electric vehicles. An electric tractor is powered by the vehicle battery. The motor converts electric energy into mechanical energy and drives the wheels through the drive train. Therefore, the electric tractor model is a modular mathematical model for the battery, motor, drive train, and drive wheel. A class of high-order terminal sliding mode control strategies is adopted to establish the relative rotational angles of drive wheels, driving angular speeds, and motor angular speeds as input, and driving angular speeds and motor angular speeds as output. This process ensures stable operating speed and good working quality under the operating conditions and achieves small-scale unattended driving. The output is a nonlinear system state equation. An n-order derivative continuous function is introduced to design the terminal sliding surface of the sliding mode. A control function to reduce chattering is also designed to ensure that the output function converges at the finite time and the existing sliding stage achieves zero steady-state error. Simulation results of the whole electric tractor model show that the speed remains stable under the condition of outside interference, and experiments verify the feasibility of the control strategy.

Concrete slabs are typically subjected to impact loading, and the selection of the equations of state and failure criteria has significant effects on the dynamic mechanical behavior of concrete. One of the most commonly adopted impact loading is projectile impact. In this study, the optimization analysis of the equation of state and failure criterion for rigid projectile penetration, which are often available for theoretical models, were analyzed using regression evaluation methods. Subsequently, based on the analysis results, a multi-phase model for the penetration of rigid projectiles into concrete was established which combined with the dynamic cavity expansion theory. Finally, the prediction results of the proposed model were compared with existing experimental data and prediction results of existing penetration models. The results showed that the prediction model has a wide range of applicability and high accuracy. • A multi-stage penetration model for predicting the damage behavior of concrete is proposed. • Analysis and assessment of models using regression evaluation methods. • The results show that the model is better than the commonly used penetration model. • The prediction model results have a wide range of applicability and high accuracy. [ABSTRACT FROM AUTHOR]

In this work we present new analytical (i.e., without computer modeling) method for calculating the dependence of the nanocrystal melting temperature both on pressure and on the size (number of atoms N) and surface shape of the nanocrystal. This method is based on the paired Mie – Lennard-Jones interatomic interaction potential, and takes into account the dependence of both the state equation and other lattice properties on the size and shape of the nanocrystal. For the first time, the dependences of the melting temperature on the pressure P , size N , and shape f of the nanocrystal were obtained. Calculations have been performed for gold, platinum and iron. It is shown that at any pressure, the melting point T m (P , N , f) decreases both with an isomorphic-isobaric (f , P – const) decrease in the number of N atoms, and with an isomeric-isobaric (N , P – const) deviation of the nanocrystal shape from the energy-optimal shape. It is shown that the value of the baric derivative of the melting temperature T m ′(P) for a nanocrystal at low pressures is greater, and at high pressures less than the T m ′(P) value for a macrocrystal. At this, the dependence of the T m ′(P) function on the nanocrystal size is insignificant, i.e., at constant N-f -arguments, the baric dependences T m (P , ∞) and T m (P , N , f) are practically parallel. It is indicated how this method can be applied for experimental evaluation of the pressure under which a nanocrystal is located in a refractory matrix. • Method for calculate T m (P) dependence on size and nanocrystal shape was developed. • The T m (P) dependences were calculated for cub and rod Au nanocrystal of 306 atoms. • The T m (P) decreases inatoms number decrease, or inshape deviationofoptimal ones. • Baric derivative of T m (P) for nano at low P big and at high P less than for macro. • Method can evaluate of P under which a nanocrystal located in a refractory matrix. [ABSTRACT FROM AUTHOR]

In this paper, exact solutions with a linear velocity field are sought for the gas dynamics equations in the case of the special state equation and the state equation of a monatomic gas. These state equations extend the transformation group admitted by the system to 12 and 14 parameters, respectively. Invariant submodels of rank one are constructed from two three-dimensional subalgebras of the corresponding Lie algebras, and exact solutions with a linear velocity field with inhomogeneous deformation are obtained. On the one hand of the special state equation, the submodel describes an isochoric vortex motion of particles, isobaric along each world line and restricted by a moving plane. The motions of particles occur along parabolas and along rays in parallel planes. The spherical volume of particles turns into an ellipsoid at finite moments of time, and as time tends to infinity, the particles end up on an infinite strip of finite width. On the other hand of the state equation of a monatomic gas, the submodel describes vortex compaction to the origin and the subsequent expansion of gas particles in half-spaces. The motion of any allocated volume of gas retains a spherical shape. It is shown that for any positive moment of time, it is possible to choose the radius of a spherical volume such that the characteristic conoid beginning from its center never reaches particles outside this volume. As a result of the generalization of the solutions with a linear velocity field, exact solutions of a wider class are obtained without conditions of invariance of density and pressure with respect to the selected three-dimensional subalgebras.

Control rod drop is the key part of ensuring the safety of nuclear reactor shutdown. Aiming at the control rod drop problem, we established a physical model of the control rod drive line. The proposed model considers the influence of the absorbing rod's position and hence evaluates the resultant force accurately on the control rod during the whole dropping process. Based on the physical model, a unified coupling state equation on the control rod drop and fluid flow is developed by integrating the motion variables of the control rod and the fluid into a state vector. A time step adaptive symplectic (TSAS) algorithm is proposed to solve the proposed state equation. The TSAS algorithm efficiently and stably predicts the motion states of the control rod and the fluid synchronously and accurately captures the sudden change of flow state. Numerical examples confirm the correctness of the proposed model and the TSAS algorithm. Sensitivity analysis is also conducted to discuss the effects of different parameters on the control rod drop, which provides reference and help for the design and manufacturing of the control rod drive line. [ABSTRACT FROM AUTHOR]

An analytical method for calculating the parameters of electroneutral vacancy formation and self-diffusion of atoms in a single-component crystal is proposed. The method is based on the four-parameter pairwise Mie–Lennard-Jones interatomic interaction potential. The method allows calculation of all activation process parameters, that is, Gibbs energy, enthalpy, entropy, and volume, for both the vacancy formation process and the self-diffusion process. The method is applicable at any pressure (P) and temperature (T). The temperature dependences of the activation process parameters for gold have been calculated from T = 10 K–1330 K along two isobars, P = 0 and 24 GPa. It is shown that, at low temperatures, due to quantum regularities, activation parameters strongly depend on temperature, and the entropy of activation processes in this region has a negative value. In the high-temperature region, the probability of vacancy formation and the self-diffusion coefficient pass into classical Arrhenius dependences, with a weakly temperature-dependent enthalpy and a positive value of the activation process entropy. Good agreement has been obtained with estimated activation parameters for gold in the literature. It is shown that at T = 0 K the activation process parameters reach their minima: the Gibbs energy, enthalpy, and volume of the activation process all become zero, and the minimum of the activation process entropy lies in the negative region. The connection of the proposed calculation method with the Varotsos cBΩ model is discussed. Temperature dependences of the enthalpy of the activation process for gold. Curves 1 and 2 – calculation of enthalpy for vacancy formation, curves 3 and 4 – calculation of enthalpy for atom delocalization. Solid curves 1 , 3 , 5 – isobars P = 0, dashed curves 2 , 4 , 6 – isobars P = 24 GPa. [Display omitted] • A new analytical method for calculating activation parameters is proposed. • Activation parameters for Au have been calculated from 10 to 1330 K for P = 0 and 24 GPa. • It is shown that at low temperatures the entropy of the activation process is negative. • For Au, use of the Arrhenius equation is incorrect at T < 200 K. • It is shown that at T = 0 K the parameters of the activation process reach minima. [ABSTRACT FROM AUTHOR]

In this paper, exact solutions with a linear velocity field are sought for the gas dynamics equations in the case of the special state equation and the state equation of a monatomic gas. These state equations extend the transformation group admitted by the system to 12 and 14 parameters, respectively. Invariant submodels of rank one are constructed from two three-dimensional subalgebras of the corresponding Lie algebras, and exact solutions with a linear velocity field with inhomogeneous deformation are obtained. On the one hand of the special state equation, the submodel describes an isochoric vortex motion of particles, isobaric along each world line and restricted by a moving plane. The motions of particles occur along parabolas and along rays in parallel planes. The spherical volume of particles turns into an ellipsoid at finite moments of time, and as time tends to infinity, the particles end up on an infinite strip of finite width. On the other hand of the state equation of a monatomic gas, the submodel describes vortex compaction to the origin and the subsequent expansion of gas particles in half-spaces. The motion of any allocated volume of gas retains a spherical shape. It is shown that for any positive moment of time, it is possible to choose the radius of a spherical volume such that the characteristic conoid beginning from its center never reaches particles outside this volume. As a result of the generalization of the solutions with a linear velocity field, exact solutions of a wider class are obtained without conditions of invariance of density and pressure with respect to the selected three-dimensional subalgebras. [ABSTRACT FROM AUTHOR]

An analytical method is proposed for calculating the properties of a disordered Au–Fe substitution alloy both with fcc and with bcc structures. The parameters of the Mie–Lennard-Jones pairwise interatomic potential for the fcc and bcc structures of Au and Fe are determined. Based on these parameters, the concentration dependences of the properties of the fcc and bcc structures of the Au–Fe alloy are calculated. It is shown that the concentration dependences are nonlinear and agree with the results obtained for fcc-Au-Fe by using density functional theory method. The changes in the lattice properties of the Au–Fe alloy under the fcc-bcc structural phase transition at a pressure of P = 0 and a temperature of T = 300 K are calculated. Based on the changes in the properties at the fcc-bcc transition, it is concluded that iron plays a major role in the phase transition in the Au–Fe alloy. The appearance of a metastable amorphous structure in a wide range of concentrations around the fcc-bcc transition in an Au–Fe alloy was explained. In the framework of the RP-model of a nanocrystal, the displacement of the iron concentration (C f), at which the fcc-bcc phase transition occurs, due to a decrease in the nanocrystal size was calculated. It is shown that at an isochoric-isothermal decrease of the atoms number (N) in an Au–Fe nanocrystal, the C f value increases. For a nanocrystal with a fixed of atoms number and a constant surface shape, the C f value increases at an isochoric increase in temperature, and the C f value decreases at an isothermal decrease in density. Calculations have shown that at N < 59 900 for the Au 1 – C Fe C alloy at P = 0, T ≤ 300 K and at any iron concentration, the fcc structure of the nanocrystal is more stable than the bcc structure. [Display omitted] • The changes of the Au–Fe alloy properties at the fcc-bcc transition are calculated. • It is shown that Fe plays a major role in the phase transition in the Au–Fe alloy. • The appearance of an amorphous structure at the fcc-bcc transition was explained. • Change in the transition parameters with a decrease of nanocrystal size is studied. • It is shown that at N < 59 900 the fcc structure is more stable than bcc structure. [ABSTRACT FROM AUTHOR]