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The event-based state estimation problem is investigated for a class of complex valued neural networks with mixed delays. By utilizing the measurement output, a novel event-triggering scheme is introduced to reduce the frequency of updating while ensuring estimation performance. A waiting time is first employed to avoid the Zeno phenomenon. By using the Lyapunov direct method and some properties of complex-valued matrix, a sufficient criterion is established to guarantee the globally asymptotic stability for the error system. The weighted parameters and gain matrices are designed by resorting to the feasible solution of matrices inequalities. Finally, a numerical example and its simulations are presented to illustrate the effectiveness of proposed approach.
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The complex non-linear coupling generated in spatial cooperation process of mobile manipulators, makes it extremely tedious to model directly for spatial cooperative systems with Lagrange equation or Newton-Euler method. A dynamic modeling method, combining Udwadia-Kalaba (U-K) method with Lagrange equation, for spatial cooperation of dual mobile manipulators is explored. The load was simplified as a connecting link while modeling. The center of load was selected to be disconnected for decomposition, so that the lack of constraint information between the end joint angle and the end link angle caused by disconnecting the end joint of the manipulator is avoided; the segmented two subsystems were modeled with Lagrange equation, thus, the dynamic model of subsystems was obtained. The inherent geometric relationships of cooperative system were introduced in the form of constraints, and the U-K method was applied to obtain the dynamic model of cooperative system. The computation for modeling is reduced. Finally, the accuracy of the model was verified by numerical simulation.
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Structural vibrations of the ultra-large structures during on-orbit assembly should be prevented to the maximum extent, because of the extreme flexibility and low natural frequencies. The assembling process is divided into four stages: grasping stage, position-attitude adjusting and stabilizing stage, mounting stage, and crawling stage. This paper focuses on the mounting stage, and a collinear assembly trajectory planning method is proposed to prevent structural vibrations. First, a dynamic model of the on-orbit assembly system (including the main structure, the space robot, and the assembling structure) is established based on natural coordinate formulation and absolute node coordinate formulation. Second, the requirements of collinear assembly are transformed into a trajectory planning problem of the space robot. The distance from the center of mass of the space robot to the main structure should remain unaltered, which is main idea of the proposed collinear assembly method. Numerical simulation results show that the proposed assembly method can effectively prevent the transverse motions of the ultra-large structure and reduce the required grasping moment. Finally, the influences of the system parameters on the dynamic response of the assembly process are studied, which provides a theoretical basis for the on-orbit assembly of ultra-large spacecraft.
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The nonlinear vibration responses of functionally graded shells with different cone angles under external load are studied in this paper. Firstly, the Voigt model was employed to describe the physical properties along the thickness direction of FGMs conical shells. Then, the motion equations were derived based on the first shear deformation theory, von Kármán geometric nonlinearity and Hamilton’s principle. Next, the Galerkin method was applied to discretize the motion equations and the governing equations was simplified into a single degree of freedom nonlinear vibration differential equation based on the Volmir’s assumption. Finally, the nonlinear motion equation was solved by the harmonic balance method and Runge-Kutta method, and the amplitude frequency response characteristic curves of FGMs conical shell were obtained. The effects of different material distribution function and the ceramic volume fraction exponents on the amplitude frequency response curve of conical shell were discussed. The bifurcation diagrams of conical shells with different cone angles and time process diagrams and phase diagrams with different excitation amplitudes were described. The motion characteristic was characterized by Poincaré map. The results show that FGMs conical shell presents the nonlinear characteristics of "hardening" spring. The chaotic motion of FGMs conical shell is restrained and FGMs conical shell is not prone to produce motion instability with the increase of cone angle. The motion of FGMs conical shell presents a process from periodic motion to multi-periodic motion and then to chaos with the increase of excitation amplitude.
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The dual-phase-lag thermoelasticity theory with memory-dependent derivative can perfectly describe the phenomenon of non-Fourier heat conduction, nevertheless, it has not been comprehensively considered: the mechanical response of materials aroused by the size-dependent effects and the influence of multiple coupling effects such as magnetic, thermal and elastic fields. A dual-phase-lag thermoelasticity theory considering memory dependent effect and non-local effect is established. Based upon the revised theory, the magneto-thermoelastic coupling problem of a thin plate subjected to a cyclical heat source is investigated. First the governing equations of the problem are formulated. Then combining the boundary conditions and initial conditions, the solution of the problem is obtained by using Laplace transform and inverse transform techniques. Last, the effects of magnetic field, phase lag, time-delay, kernel function, non-local effect and time on the dimensionless quantities were investigated respectively, which provided a powerful reference for the dynamic response of micro-scale materials.
Abstract(39) HTML(22) PDF(2)
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The effective bulk modulus and the effective in-plane shear modulus of nano-fiber composites are investigated using interface model and interphase model based on the generalized self-consistent method, the closed-form analytical solutions of effective bulk modulus and all equations for predicting effective in-plane shear modulus by numerical method based on the two models are presented. Using the interface model, interface effects of the effective bulk modulus and the effective in-plane shear modulus are discussed by use of numerical examples. Further research demonstrates that the analytical formula of the effective bulk modulus and the numerical results of the effective in-plane shear modulus derived from the interface model can be obtained again from the interphase model. An example of aluminium containing nano voids shows that the effective bulk modulus and the effective in-plane shear modulus predicted by the interface model have large deviations from that of the interphase model when the void radius is small, however for larger void radius, the difference is small.
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The projection algorithm is one of the main methods to solve variational inequality problems. At present, the research on projection algorithms usually requires the assumption that the mapping is monotone and Lipschitz continuous, but in practical problems, these assumptions are often unsatisfied. In this paper, a new double projection algorithm for solving non-monotone variational inequality problems is proposed by using the line search method. Under the assumption that the mapping is uniformly continuous, it is proved that the sequence generated by the algorithm strongly converges to a solution of variational inequalities. The numerical experiments illustrate effectiveness and superiority of the proposed algorithm.
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In order to identify the instantaneous frequency of time-varying signals, this paper derives the theoretical relationship between the frequency in a signal and rotational angle α in a fractional Fourier transform. It is demonstrated that the fractional Fourier transform is actually an algorithm of ordinary Fourier transform combined with telescopic translation window. A general expression of signal instantaneous frequency in the fractional Fourier domain is thereafter formulated so that structural instantaneous frequency can be extracted accordingly. The feasibility and reliability of proposed method is verified by a simulated nonlinear frequency modulation signal and a numerical example of a three-degree-of-freedom damped time-varying structure system. The results show that the proposed method is in good agreement with the theoretical values and the method has a certain degree of anti-noise capability. Subsequently, the proposed method is capable of identifying the instantaneous frequency of time-varying structures.
Abstract(39) HTML(21) PDF(8)
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Based on Lyapunov stability theory, matrix analysis method, linear matrix inequality methods, etc, the generalized H2 control of singularly perturbed uncertain control systems with time-varying delay and control input and disturbance input is studied. A memory state H2 generalized controller is designed, the decision theorem of the specific design method given. Quoting new lemma for delay dependent and delay independent cases, the relatively less conservative stability criterion is derived. The obtained results are linearized, the selected numerical examples are used to verify the effectiveness and feasibility to the derived conclusions. It is pointed out that the closed-loop system is asymptotically stable in the whole range from zero to singular perturbation upper bound, which expands the generalized H2 stability space and reduces the L2-L performance index. By comparing the stability state parameter index with the related literatures, it is shown that the proposed method has certain advantages and less conservatism, and is suitable for standard and non-standard cases.
Abstract(46) HTML(38) PDF(6)
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The sine-cosine method is applied to the wave equation of nonlinear elastic rod, and some new periodic and soliton solutions of the equation is obtained (material constant n is a constant different from 1). The graphs of some solutions are given through math software. The results are helpful to further research on existence of solitary waves in the nonlinear elastic rod.
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2022, Volume 43, Issue 7 publish date：July 01 2022
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2022, 43(7): 707-718.   doi: 10.21656/1000-0887.420320
Abstract(120) HTML(53) PDF(56)
Abstract:

In the cases of Reynolds number Re=3 000~50 000, Stokes number Stk=0.1~10, Dean number De=1 400~2 800, the orientation and deposition characteristics of cylindrical particles with aspect ratio β=2~12 in turbulent flow in curved tubes were studied. The motion of cylindrical particles was described under the slender body theory combined with Newton’s 2nd law. The orientation distribution function of cylindrical particles was given by the Fokker Planck equation. The mean velocity of the flow was obtained by solving the Reynolds-averaged Navier-Stokes equation and the Reynolds stress equation. The turbulent fluctuating velocity acting on particles was described with the kinetic simulation sweeping model. By solving the equations of the turbulent flow, the particle motion and the orientation distribution function, the orientation distributions of particles on the cross sections in different axial positions and the outlet were obtained and analyzed. The effects of various parameters on the deposition rate of particles were discussed. The results showed that, the main axis of particles turns toward the flow direction with the increase of Stk and β, and the decrease of De and Re. The deposition rate of particles increases with De, Re and β. However, it shows a non-monotonic trend with the change of Stk

. The work has reference values for practical engineering application.

2022, 43(7): 719-726.   doi: 10.21656/1000-0887.420299
Abstract(98) HTML(43) PDF(54)
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For the transverse vibration of slightly curved pipes, a dynamic mechanical model based on the Timoshenko beam theory was established for the 1st time. The natural vibration characteristics of slightly curved pipes under the influence of the fluid flow were analyzed. With the generalized Hamiltonian principle, the governing equation of the transverse vibration of slightly curved pipes under the fluid-structure coupling effect was derived. Based on the Galerkin truncation, the natural frequencies of slightly curved pipes were obtained with the generalized eigenvalue method. Effects of the fluid velocity and the initial deflection on the natural vibration characteristics of the pipe were studied. The equivalent stiffness and damping method-based finite element simulation of the natural vibration of the slightly curved pipe was developed. Then through the finite element numerical simulation, the results of the Galerkin truncation method and the effectiveness of the Timoshenko model were verified. The work shows that, both the fluid velocity and the initial deflection have significant effects on the natural frequencies of slightly curved pipes.

2022, 43(7): 727-739.   doi: 10.21656/1000-0887.420325
Abstract(64) HTML(53) PDF(25)
Abstract:

The flow boiling phenomenon in a channel with multiple rectangular heaters under a constant wall temperature was numerically studied with the lattice Boltzmann method. The effects of spacings between heaters, heater lengths and heater surface wettabilities on the bubble morphology, the bubble area and the heat flux on the heater surface, were studied. The results show that, the bubble growth rate increases with the spacing between heaters. The larger the bubble area is, the earlier the nucleated bubbles will leave the heater surface. The corresponding boiling heat transfer performance increases by 12% with the spacing between heaters growing from 250 lattices to 1 000 lattices. On the other hand, the longer the heater length is, the earlier the bubble will nucleate and leave the heater surface, and the better the boiling heat transfer performance will be. The boiling heat transfer performance increases by 13% with the heater length rising from 16 lattices to 22 lattices. In addition, the bubble nucleates later on the hydrophilic surface than on the hydrophobic surface. Compared with the hydrophilic surface, the hydrophobic surface retains residual bubbles after the leaving of bubbles from the heater. The average heat flux and the bubble area of the hydrophilic surface are less than those of the hydrophobic surface. With the contact angle changing from 77° to 120°, the heat transfer performance increases by 26%. Finally, the orthogonal test results indicate that, the wettability of the heat exchanger surface has the greatest influence on the flow boiling heat transfer performance, while the heater length has the least influence.

2022, 43(7): 740-751.   doi: 10.21656/1000-0887.420171
Abstract(54) HTML(32) PDF(20)
Abstract:

A Mindlin plate theory for micro-nano structures was proposed based on the couple stress theory. A length parameter was introduced to consider the size effect, and the constitutive equations for the micro-nano Mindlin plate were derived in view of the transverse shear deformation. The buckling and free vibration governing equations in terms of displacements and the slope functions of the shear deformation micro-nano plate were further deduced with the force equilibrium conditions. The analytical solutions of buckling and free vibration for the shear deformation micro-nano plate were obtained through separation of the displacement and rotation variables in space and time domains. Two scenarios of boundary conditions were analyzed: SSSS (simply supported by 4 edges) and SCSC (2 opposite edges simply supported and other 2 edges clamped). A MATLAB program was developed to compute the critical buckling and natural frequencies with different values of dimensional parameters, aspect ratios and length-to-thickness ratios. The research results, in comparison with those from the ABAQUS finite element analysis and previous literatures, are consistent with the latter ones. The examples show that, the size effects significantly influence the buckling load and the natural frequency.

2022, 43(7): 752-760.   doi: 10.21656/1000-0887.420317
Abstract(80) HTML(57) PDF(18)
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2022, 43(7): 761-771.   doi: 10.21656/1000-0887.420128
Abstract(56) HTML(33) PDF(17)
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In order to improve the efficiency of stochastic model updating and reduce the amount of calculation, a stochastic model updating method based on Kriging model and lifting wavelet transform was proposed. Firstly, the lifting wavelet transform was performed on the acceleration frequency response function, and the 5th-level approximate coefficients were extracted to replace the original frequency response function; secondly, the Latin hypercube sampling was applied to sample the parameters to be updated and the corresponding approximate coefficients as the outputs to build the Kriging model. A butterfly optimization algorithm with Lévy flight (LBOA) was proposed and used to improve the accuracy of  Kriging model; finally, with the goal of minimizing the Wasserstein distance, the mean values of the parameters to be updated were solved with the whale optimization algorithm. The results of the test function show that, the LBOA greatly improves in terms of optimization, convergence accuracy and stability. The updating errors of the numerical examples are all less than 0.4%, and indicate the high accuracy and efficiency of the proposed model updating method.

2022, 43(7): 772-782.   doi: 10.21656/1000-0887.420079
Abstract(73) HTML(37) PDF(25)
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Prediction of the influence of each component of recycled aggregate concrete on the macroscopic mechanics properties of recycled aggregate concrete is a way to develop the basic mechanics properties of recycled aggregate concrete. For this purpose, a meso-equivalent model was established according to the meso-structure composition of recycled aggregate concrete. Based on the torsional deformation theory, the meso-inclusion theory, the elastic equivalent thought and the M-T model, the prediction model for macroscopic mechanics properties of recycled aggregate concrete composed of natural aggregate, old interface, old cement mortar, new interface and new cement mortar, was deduced. The prediction results show that, with the increase of the recycled aggregate replacement rate, the content of cement mortar and the porosity of recycled aggregate concrete rise, resulting in the increase of Poisson’s ratio of recycled aggregate concrete, and the decreases of the elastic modulus, the shear modulus and the volume modulus. The model well predicts the changing trend of the macroscopic mechanics properties of recycled aggregate concrete with the increase of the recycled aggregate replacement rate, and provides a simple and practical new way to the research and analysis of the basic mechanics properties of recycled aggregate concrete.
2022, 43(7): 783-791.   doi: 10.21656/1000-0887.420220
Abstract(59) HTML(46) PDF(25)
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The sampling consensus of 2nd-order multi-agent systems with time-varying topology was investigated based on the constant position difference and the consistent speed. Firstly, the virtual leader was introduced and the sampling consensus problem of multi-agent systems was transformed into the stability problem of the corresponding error system. Secondly, with estimation of the sampling errors, the influence of sampling errors on system consistency was studied. Finally, by virtue of the Lyapunov stability theory, the stability of the constructed error system was analyzed, and a sufficient condition for the stability of the error system was given. The numerical simulation results verify the effectiveness and correctness of the theoretical analysis.

2022, 43(7): 792-801.   doi: 10.21656/1000-0887.420294
Abstract(62) HTML(41) PDF(28)
Abstract:

The mathematical program with switching constraint (MPSC) problem makes a new-type optimization issue in recent years. Due to the existence of switching constraints, the common constraint specification is not satisfied, so that the convergence results of existing algorithms can not be directly applied to this problem. The sequential quadratic programming (SQP) method was applied to solve the problem, and to prove that the clustering point of the solution sequence of the subproblem is the Karush-Kuhn-Tucker point of the original problem under the linear independent constraint specification with the switching constraint. At the same time, in order to improve the relationship between stationary points, the equivalence between the strong stationary point and the KKT point was proved. Finally, the numerical results show that, the sequential quadratic programming method is feasible to deal with this type of problems.

2022, 43(7): 802-815.   doi: 10.21656/1000-0887.420194
Abstract(129) HTML(37) PDF(25)
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In order to meet the requirement of high accuracy and high resolution in computational fluid dynamics (CFD), a new reference smoothness indicator was proposed to reduce the numerical dissipation of the classical 3rd-order weighted essentially non-oscillatory (WENO) scheme. The construction method is different from the classical WENO-Z scheme. It is obtained through the L2-norm approximation of the derivatives of the reconstruction polynomials of the whole global stencil, and the linear combination of the derivatives of the reconstruction polynomials on the candidate sub-stencils. With this calculation method, higher-order reference smoothness indicators can be obtained than the WENO-Z scheme. In addition, different reference smoothness indicators can be obtained by change of the value of free parameter

\begin{document}$\varphi$\end{document}

. A series of numerical examples prove the effectiveness of the reference smoothness indicator.

2022, 43(7): 816-824.   doi: 10.21656/1000-0887.420109
Abstract(149) HTML(59) PDF(31)
Abstract:

A macroscopic nonlinear Keller-Segel model for chemotactic cell migration was considered, where the existence region of the model is a bounded convex one on

\begin{document}$\varOmega\subset\mathbb{R}^N(N\geqslant2)$\end{document}

. The global existence of the solution on

$\varOmega\subset\mathbb{R}^3$

was obtained by means of the energy estimate method. The lower bound of the blow-up time was proved for

$N=3$

and

$N=2$

.

2016, 37(2): 149-159.   doi: 10.3879/j.issn.1000-0887.2016.02.004
[Abstract](1172) [PDF 5386KB](743)

2017, 38(1): 1-31.   doi: 10.21656/1000-0887.370578
[Abstract](1227) [PDF 1039KB](1423)

《随机振动的虚拟激励法》自1985年正式发表以来，逐渐得到许多工程领域的认可和采用，解决了很多重要而困难的工程问题.该方法不但被国内某些工程规范所推荐，而且被3种国际工程手册成章刊载，在国际上亦占有了一席之地.该文是笔者参考了数百篇国内外论文，依据其中一部分在11个工程领域对虚拟激励法的应用和一些学者的评论所撰写的综述.借以让更多工程技术人员和研究者对虚拟激励法有较为全面的了解，以结合各自工程领域更有效地开展对随机振动理论和方法研究成果的应用和发展.
2017, 38(1): 44-59.   doi: 10.21656/1000-0887.370571
[Abstract](1153) [PDF 647KB](950)

2020, 41(3): 339-352.   doi: 10.21656/1000-0887.400176
[Abstract](726) [FullText HTML](81) [PDF 405KB](293)

2016, 37(12): 1272-1281.   doi: 10.21656/1000-0887.370546
[Abstract](830) [PDF 3862KB](614)

2017, 38(1): 32-43.   doi: 10.21656/1000-0887.370336
[Abstract](1190) [PDF 683KB](2058)

2016, 37(1): 73-83.   doi: 10.3879/j.issn.1000-0887.2016.01.006
[Abstract](1008) [PDF 1871KB](688)

2020, 41(2): 204-215.   doi: 10.21656/1000-0887.400159
[Abstract](791) [FullText HTML](80) [PDF 1329KB](400)

2016, 37(8): 791-803.   doi: 10.21656/1000-0887.370056
[Abstract](840) [PDF 589KB](831)

2017, 38(4): 369-398.   doi: 10.21656/1000-0887.370328
[Abstract](1279) [PDF 6800KB](1188)

2008, 29(8): 947-953.
[Abstract](3008) [PDF 460KB](25)
Abstract:
A study of double dissintilar orthotropic composite materials interfacial crack was made by constivcting new stress functions and employing the method of composite material complex.In the case that the characteristic equations' discriminants are all more than zero,the theoretical fonmula of the stress field and the displacement field near the mode Ⅰ interface crack tip,without oscillation and inter-embedding between the interfaces of the crack were delved.
2002, 23(5): 441-451.
[Abstract](5622) [PDF 395KB](124)
Abstract:
The solution and computational aspects on nonlinear deflection of Yongjiang Railway Bridge in Ningbo were investigated.An approximate iteration algorithm on nonlinear governing equation was presented,and the obtained results show that,if altitude difference and span of the riverbanks are taken as 5 meters and 100 meters,respectively,the maximum gradient in the middle of the bridge exceeds 5%,much larger than maximum allowance gradient in railway design code.Therefor,a new solution scheme for decreasing gradient of the bridge is put forward,that is,the altitude difference between two riverbanks can be decreased to about 1/10 of the initial magnitude by building roadbeds with 0.5% gradient and 1 kilometer length at two riverbanks.As a direct result,the deflection gradient of the railway bridge is much reduced and the value is between 0.5%~0.6%.
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Founded in 1980 ( monthly )

Supervisor：Chongqing Jiaotong University

Founder：CHIEN Weizang

Honorary Chief Editor：ZHONG Wanxie

Editor-in-Chief：LU Tianjian

ISSN 1000-0887

CN 50-1060/O3