Calculation and experimental investigation of torsion of all-rubber and rubber-cord clutches under large deformations

On the basis of a mathematical model of large deformations of homogeneous and fiber-reinforced bodies of revolution, the deformation of all-rubber and rubber-cord clutches made by using the tire technology is investigated. The results of a theoretical and numerical analysis of torsion of the clutches are compared with experimental data.     

Shear strength and laws of shear deformation of some cross-linked resins

The authors present the results of an experimental investigation and comparison with theory of certain laws of shear deformation and shear strength for rigid cross-linked resins. The possibility of describing the state of strain of homogeneous isotropic polymers by means of the generalized nonlinear Maxwell equation is considered. The results of an investigation of thin-walled tubular specimens of three cross-linked polymers based on epoxy resins and one linear polymer are offered as a check on the corresponding theoretical relations. The agreement between the theoretical and experimental results is perfectly satisfactory. Experimental values of the high-elastic constants in shear and tension have been determined. It is shown that the theoretical and experimental relations coincide with satisfactory accuracy. Certain experimental data on the comparative conditions of failure in shear and tension are presented.Mekhanika Polimerov, Vol. 2, No. 2, pp. 214–228, 1966     

Creep stability of polymer rods

The author examines the problem of the buckling of a hinger rod of rigid homogeneous polymer material under constant load. The results of an experimental investigation are presented. The theoretical calculations are based on the nonlinear generalized Maxwell equation. A numerical solution has been obtained on a computer. The results of this solution are compared with the experimental data. An analytic solution that makes it possible to estimate certain limiting values is obtained for the linearized equation.Mekhanika Polimerov, Vol. 4, No. 1, pp. 145–150, 1968     

Mechanical behavior of cylindrical laminated plastic shells

The static and dynamic behavior of a cylindrical glass-reinforced plastic shell with an open cross section under long-term loading and unloading has been experimentally and theoretically investigated. The experimental results are compared with the theoretical data obtained using a geometrically nonlinear theory based on the Kirchhoff hypothesis. For calculation purposes the glass-reinforced plastic is assumed to be a homogeneous orthotropic linearly elastic material.Building Research Institute, Prague. Translated from Mekhanika Polimerov, No. 1, pp. 110–115, January–February, 1976.     

A Deformation Model for Dispersely Failing Elastoplastic Unidirectionally Reinforced Composites

A calculation model is proposed for unidirectionally reinforced elastoplastic composites capable of gradually accumulating disperse microdamages under loading. The composite is assumed to be a homogeneous transversely isotropic solid. To describe its elastoplastic behavior, an incremental plasticity theory with a nonlinear combined hardening mechanism is invoked. At each point of the solid, its damage is characterized by a centrally symmetric scalar function on a unit sphere. This function is approximated by a fourth-rank tensor, which is used for describing the degradation of the elastic properties of the solid due to the accumulation of disperse microdamages. It is shown how to determine, using the known experimental data, all material constants appearing in the theoretical relations suggested.     

在线Logistic回归

针对连续数据流分类问题,基于在线学习理论,提出一种在线logistic回归算法.研究带有正则项的在线logistic回归,提出了在线logistic-l2回归模型,并给出了理论界估计.最终实验结果表明,随着在线迭代次数的增加,提出的模型与算法能够达到离线预测的分类结果.本文工作为处理海量流数据分类问题提供了一种新的有效方法.     

Modelling yarn balloon motion in ring spinning

Air-drag on a ballooning yarn and balloon shape affect the yarn tension and ends-down (yarn breakage), which in turn affects energy consumption and yarn productivity in ring spinning. In this article, a mathematical model of yarn ballooning motion in ring spinning is established. The model can be used to generate balloon shape and predict tension in the ballooning yarn under given spinning conditions. Yarn tension was measured using a computer data acquisition system and the balloon shapes were captured using a digital camera with video capability during the experiments using cotton and wool yarns at various balloon-heights and with varying yarn-length in the balloon. The air-drag coefficients on ballooning cotton and wool yarns in ring spinning were estimated by making a “best fit” between the theoretical and experimental turning points. The theoretical results were verified with experimental data. The effects of air-drag and balloon shape on yarn tension are discussed.     

Bifurcations in a diffusive predator–prey model with predator saturation and competition response

A diffusive predator–prey model with predator saturation and competition response subject to homogeneous Neumann boundary conditions is considered in this paper. We find that the spatially homogeneous and non‐homogeneous periodic solutions through all parameters of the system are spatially homogeneous. To verify our theoretical results, some numerical simulations are also carried out. Copyright © 2014 John Wiley & Sons, Ltd.     

An analysis of stress wave propagation in slender bars using a discrete particle approach

In this paper, a discrete particle approach is developed for the quantitative analysis of stress wave propagation in metal bars. Though linear forces are emphasized, nonlinear forces are also considered. Cylindrical, tapered, homogeneous, and nonhomogeneous bars are studied. Computer results show most favourable agreement with available theoretical and experimental results.     

Spatiotemporal dynamics analysis and optimal control method for an SI reaction-diffusion propagation model

In the new social media era, it is becoming increasingly important to explore the propagation rules for rumors in social networks. This article is concerned with investigating a diffusive susceptible-infected rumor propagation model with a nonlinear propagation function in a spatially heterogeneous environment. We establish the uniform persistence and analyze the asymptotic behavior of the rumor-spreading steady state for the spatially heterogeneous model when one of the diffusion coefficients tends to zero. Moreover, to better reflect the effect of a time delay on the process of rumor propagation, we establish a spatially homogeneous model with a time delay and prove the existence and local stability of the corresponding equilibrium point. Furthermore, the optimal control in the spatially homogeneous environment case is derived. Finally, several numerical simulations are performed to verify the theoretical results in both spatially heterogeneous and spatially homogeneous systems.     

Aeroelastic behavior of a typical section with shape memory alloy springs: Modeling nonhomogeneous distribution of state variables

In this paper, a two-degree-of-freedom (namely, plunge and pitch) aeroelastic typical section with shape memory alloy helical springs in the pitch degree-of-freedom is modeled. A linear aerodynamic model is employed to predict the unsteady loads. The shape memory springs model is based on classical models modified by the von Mises pure shear assumption. Nonhomogeneous distributions of shear strain, shear stress and martensitic fraction in the wire cross-section are represented by axi-symmetric annular regions. The numerical predictions of the effects of pseudoelastic hysteresis of shape memory alloy springs on the aeroelastic behavior of the typical section when both the homogeneous and nonhomogeneous cross-sectional distributions are considered in the simulations are compared with experimental data obtained in wind tunnel tests. The nonhomogeneous assumption results in good agreement between numerical predictions and experiments. Both the numerical and experimental results show that the pseudoelastic hysteresis of SMAs can be employed as a passive alternative to modify the behavior of aeroelastic systems.     

Hopf bifurcation analysis in a one-dimensional Schnakenberg reaction-diffusion model

In this paper, we study the Hopf bifurcation phenomenon of a one-dimensional Schnakenberg reaction-diffusion model subject to the Neumann boundary condition. Our results reveal that both spatially homogeneous periodic solutions and spatially heterogeneous periodic solution exist. Moreover, we conclude that the spatially homogeneous periodic solutions are locally asymptotically stable and the spatially heterogeneous periodic solutions are unstable. In addition, we give specific examples to illustrate the phenomenon that coincides with our theoretical results.     

A comparative analysis of moisture transport models as applied to an epoxy binder

The results of experimental and theoretical investigations into the kinetics of moisture sorption by a neat epoxy resin obtained from RAE Industries (Reapox 520, D523) are reported. The sorption process was realized in atmospheres with a constant relative humidity of 33, 53, 75, 84, and 97% and a temperature of 50°C. The results obtained showed that the diffusion behavior of epoxy resin did not obey Fick’s law under the experimental conditions considered. Consequently, the application of a non-Fickian diffusion model was necessary. For this purpose, two-phase moisture sorption models, a model with a time-dependent diffusivity, a two-phase material model, as well as relaxation and convection models of anomalous diffusion, were considered. The model parameters were obtained from the approximation of experimental sorption data. A comparative analysis of the sorption models was performed, and the specific features of their applications were estimated. The two-phase material model and the model with varying diffusivity were found to be the most suitable ones due to a good agreement between calculation results and experimental data and the rather small (three or four) number of parameters, which make them more flexible and physically more justified than the classical Fick’s model with its two parameters. __________ Translated from Mekhanika Kompozitnykh Materialov, Vol. 43, No. 4, pp. 555–570, July–August, 2007.     

Experiments and Identifications for Finite Polymer Inelasticity

The constitutive theories intended to quantitatively account for the complicated material response exhibited by polymers include, in general, adjustable material parameters. These must be identified from experimental data obtained from the material under consideration. This contribution presents the complete procedure studying the behavior of polymers at large strains in three basic steps: i) Accomplishment of homogeneous and 3-D inhomogeneous experiments under different deformation conditions. ii) Identification of the material parameters of a constitutive model by means of gradient–based optimization methods with respect to the homogeneous experimental data. iii) Validation of the identified material parameters by comparing 3-D FE simulations to the inhomogeneous experimental data. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Model selection for Gaussian latent block clustering with the integrated classification likelihood

Block clustering aims to reveal homogeneous block structures in a data table. Among the different approaches of block clustering, we consider here a model-based method: the Gaussian latent block model for continuous data which is an extension of the Gaussian mixture model for one-way clustering. For a given data table, several candidate models are usually examined, which differ for example in the number of clusters. Model selection then becomes a critical issue. To this end, we develop a criterion based on an approximation of the integrated classification likelihood for the Gaussian latent block model, and propose a Bayesian information criterion-like variant following the same pattern. We also propose a non-asymptotic exact criterion, thus circumventing the controversial definition of the asymptotic regime arising from the dual nature of the rows and columns in co-clustering. The experimental results show steady performances of these criteria for medium to large data tables.     

CFD-半解析模型混合的管束结构流弹失稳预测方法

横向流作用下管束结构传统流弹失稳模型的建立或多或少需要获取实验流体力参数作为输入条件.因此非常需要开发一种不依赖实验数据的管束结构流弹失稳模型.该文提出了一种改进的CFD仿真与半解析方法混合的管束结构流弹失稳预测方法.采用CFD仿真方法获取半解析模型中关键的相位延迟函数,并根据速度将其表示为简单的分段函数.最终预测了横...     

Nonlinear creep of thick-walled polymer tubes under internal pressure

The process of creep in a thick-walled tube of rigid homogeneous epoxide-type polymer under under the action of a steady internal pressure is studied. A theoretical analysis has been made on the basis of a non-linear generalized Maxwell equation, taking account of two terms of the spectrum of polymer relaxation times. A comparison is given with the results of a calculation with a single term of the spectrum and according to linear theory. The theoretical results are compared with those obtained experimentally in a specially constructed apparatus. The possibility is shown of evaluating the long-term strength of a thick-walled polymer tube under the action of a steady internal pressure.Institute of Chemical Physics, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 3, pp. 493–501, May–June, 1970.     

重力载荷作用下柔性梁的结构变形与承载力分析

柔性体在承受外载荷作用时,会通过自身变形,降低所承受的外载荷.为了研究重力载荷作用下柔性梁的结构变形与承载力之间的定量关系,首先建立模拟实验分析重力载荷在梁上的分布形式;基于Timoshenko梁的大变形本构方程,建立承受重力载荷作用下大变形梁的控制方程;通过量纲分析,确定研究两个无量纲变量,结构变形数与Cauchy数...     

Existence and asymptotic behavior of solutions for a mathematical ecology model with herd behavior

In this work, we consider a prey-predator model with herd behavior under Neumann boundary conditions. For the system without diffusion, we establish a sufficient condition to guarantee the local asymptotic stability of all nontrivial equilibria and prove the existence of limit cycle of our proposed model. For the system with diffusion, we consider the long time behavior of the model including global attractor and local stability, and the Hopf and steady-state bifurcation analysis from the unique homogeneous positive steady state are carried out in detail. Furthermore, some numerical simulations to illustrate the theoretical analysis are performed to expand our theoretical results.