A nonlinear model of center-wound rolls incorporating refined boundary conditions

This article presents a novel approach for determining the displacement, strains and stresses developed in a center-wound roll. The approach consists of a nonlinear model and some refined boundary conditions. The investigation starts with a linear, displacement-based formulation and refined boundary conditions previously developed by the author. The choice of displacement-based formulation, unlike the stress-, or strain-based counterpart, allows for easy determination of relative and absolute displacements, and stress and strain components caused by the relative displacement and by the wound-in stress. The refined boundary conditions, on the other hand, take into account radial displacement compatibility at the core-roll interface, as well as between the current outer surface of the roll and the next wound-on lap, resulting in relaxation of the wound-in stress, or the loss of it. Conventional boundary conditions, on the contrast, consider only radial displacement compatibility at the core-roll interface. The nonlinear model incorporates nonlinear radial modulus of elasticity of the wound roll. It is linearized lap-by-lap, translating the nonlinear problem into a series of linear equations of banded structure. A number of examples are chosen to demonstrate that the approach is accurate, rather simple, able to account for wound-in stress loss and capable of updating web thickness. Furthermore, it can accommodate any form of nonlinear radial modulus of elasticity and any profile of wound-in stress.     

Optimal shape of prestressed disks against brittle-rupture under unsteady creep conditions

The effect of thickness distribution of circumferentially prestressed rotating disks on the localization of brittle creep rupture is analysed. For an optimal disk with arbitrary prestressing the first macrocracks appear simultaneously atN-points (N is the numbers of elements of the jump-like variable thickness of the disk) and, hence, the lifetime is maximized. The time to rupture of an optimal disk of jump-like thickness is compared with the lifetime of a disk of uniform elastic equivalent stress and of the same number of thickness elements. The time hardening theory associated with Kachanov's brittle rupture equation is applied as the constitutive equation describing unsteady creep. The optimization procedure used to determine thickness distribution is based on the iterative corrections of the element thicknesses. Apart from disks optimized without any constraints, the optimal shapes of disks under additional geometric constraints (minimal thickness) are considered.     

A kinetic model for beer production under industrial operational conditions

A kinetic model for beer production is proposed. The model takes into account five responses: biomass, sugar, ethanol, diacetyl and ethyl acetate. In contrast with previously published models, this model segregates biomass into three components: lag, active and dead cells and considers the active cells as the only fermentation agent. Experiments were first performed at laboratory scale and isothermal runs were carried out at five temperatures (8°C, 12°C, 16°C, 20°C and 24°C). Fitting of experimental data was made by non-linear regression. Parameter values calculated were similar to those given in the literature. The kinetic model was able to fit experimental data with a very good agreement. Afterwards, experiments were conducted at pilot plant scale and runs were now carried out changing temperature with time, in the industrial way. The kinetic model, with the parameter values calculated as a function of temperature, was able to predict with a very high accuracy the non-isothermal experimental data achieved. This model can be used for simulation of the industrial process under different operational conditions and for faults detection. It can also be utilized for the optimization and even for the supervised control of the process and its automatization.     

A novel FEM model for biaxial non-crimp fabric composite materials under tension

This paper presents a novel finite element based approach able to represent the complex architecture of the non-crimp fabric (NCF) composite materials. By means of the stiffness averaging method, implemented in the research oriented FEM (finite element method) code B2000, the developed model is able to simulate the NCFs mechanical performances. Applications to simple coupons loaded in tension are presented in order to demonstrate the capability and the effectiveness of the presented approach. Nevertheless, the proposed methodology can be applied and extended to all NCF geometries. First, for validation purposes the numerical results detained for a specific configuration have been compared with experimental results available from literature. Then, a parametric study has been carried out to investigate the influence of the bundle waviness on the tension stiffness. Finally, due to the degradation of the in-plane mechanical properties, the presence of the stitching has been investigated.     

深度复合模型下的土壤重金属含量预测

为提高土壤重金属含量预测的准确性,提出一种深度复合模型(DCM).以径向基神经网络(RBFNN)为基础,将基于双曲正切函数变换的概率调整和容忍准则引入遗传算法,用于RBFNN输出层参数的生成,将随梯度正负值变化而自适应调整的学习率运用到均方根反向传播(RMSProp)算法上,用于RBFNN监督学习过程中参数的优化.结合...     

Multilevel optimization of composite panels under complex load and boundary conditions

Due to their complexity and large numbers of design variables, aerospace structures, such as aircraft wings, are best optimized using a multi-level process. In addition to simplifying the optimization procedure, such an approach allows a combination of different methods to be used, increasing the efficiency of the analysis. This paper presents a technique based on the usage of exact finite strip software, VICONOPT, with the finite element analysis package, ABAQUS. The computer programme VICONOPT is computationally efficient but provides solutions for a restricted range of geometries and loading conditions. Finite element analysis allows accurate models of structures with complex geometries to be created but is computationally expensive. By combining the two, these limitations are minimised, whilst the strengths of each are exploited. The fundamental principles of this multi-level procedure are demonstrated by optimizing a series of curved composite panels under combined shear and in-plane bending subject to buckling constraints. Presented at the 7th World Congress on Computational Mechanics, LA, USA, July 2006.     

A finite element creep crack growth model for Waspaloy

Plastic and creep deformations lead to reduced stress levels ahead of the crack tip in a creep crack growth test. However, they can also cause microcracks, cavities and other defects forcing fracture. Numerous damage models are reported in the literature to describe the behavior. In this article, a damage model will be developed from different theories and will be used to describe the creep crack growth behavior of Waspaloy at 973 K. Material parameters for this model are adjusted to uniaxial creep and tensile tests. The calculated creep crack growth curves match very well with the experimental ones supporting the model.     

长玻纤增强热塑性复合材料车轮径向载荷下的强度仿真

为提高复合材料车轮仿真的准确性,采用高性能长玻纤增强热塑性复合材料作为车轮材料,探索在考虑材料各向异性的情况下联合使用Moldflow,Digimat和Abaqus对车轮强度进行仿真的方法,并针对具体车轮采用该方法按照国家标准进行径向载荷下的强度仿真与分析.研究结果表明：复合材料各向异性特性对车轮应力、应变的分布及最大值均有较大影响;在同一位置是否考虑材料各向异性影响得到的应力值最大相差达314%.该方法可提高长玻纤增强复合材料车轮强度仿真计算结果准确性,可为车轮的进一步轻量化提供参考.     

边界条件下的Fizhugh Nagumo模型斑图动力学研究

本文主要研究边界条件下FN(FiZhUgh-Nagum)模型的神经定位动力学行为,首先针对带有扩散的FN模型进行了理论研究;然后通过离散拉普拉斯算子的方法,得到了FN模型带有边界的常微分方程;接着分析了边界条件对系统斑图形态的具体影响,对混合边界不同参数取值进行了研究,得到了混合边界值和矩阵谱倒数的关系;最后通过数值模拟的方法验证了已有实验结果,解释了上述系统的斑图机制,给出了斑图形态的调控方法。     

A frequency response identification method for discrete-time processes with cyclic steady state conditions

A new frequency response identification method is presented to estimate frequency responses of discrete-time linear time-invariant processes. It provides multiple exact frequency response data set for any desired frequencies. The proposed method is applicable to all the process data types of both initial/final steady state, initial steady state/final cyclic steady state, initial cyclic steady state/final steady state and both initial/final cyclic steady state. Also, it completely removes the effect of static disturbances and shows acceptable robustness to measurement noises.     

The leontief-ford dynamic optimization model under conditions of ecological equilibrium

The ecological-economical optimization problem based on the Leontief-Ford model is investigated. Necessary and sufficient conditions of the optimal solution are described for the discrete variant of the model. Translated from Kibernetika i Sistemnyi Analiz, No. 2, pp. 73–79. March–April, 2000.     

A material optimization model to approximate energy bounds for cellular materials under multiload conditions

This paper describes a computational model, based on inverse homogenization and topology design, for approximating energy bounds for two-phase composites under multiple load cases. The approach allows for the identification of possible single-scale cellular materials that give rise to the optimal bounds within this class of composites. A comparison of the computational results with the globally optimal bounds given via rank-N layered composites illustrates the behaviour for tension and shear load situations, as well as the importance of considering the shape of the basic unit cell as part of the design process.     

A model for 1D multiphase moving phase boundary simulations under local equilibrium conditions

Two previously suggested simulation models, for multiphase simulations (Larsson and Engström, 2006; Larsson and Höglund, 2009) and diffusion controlled growth (Larsson and Reed, 2008), respectively, are unified to form a generalized model for 1D simulations of diffusion controlled growth under local equilibrium conditions where multiple phases are allowed on either side of an interface.     

A computationally efficient particle-puff model for concentration variance from steady releases

This paper presents a computationally efficient particle-puff model that can be used to calculate both average concentration and concentration variance in turbulent flows. The model is self-contained in the sense that it does not need externally supplied parameterizations of puff spread, but rather calculates the spread with an internally-built module for relative dispersion of particles—all existing particle-puff models rely on parameterizations of puff spread derived from theoretical considerations and observational data for dispersion of a point source in isotropic turbulence.Preliminary evaluations show that the model performs as well as a computationally demanding two-particle trajectory model in predicting the mean concentration and concentration variance in two different flows: isotropic turbulence and a wind tunnel boundary layer. Because of its numerical efficiency, the present particle-puff model can be built into conventional, regulatory air quality models as a module to calculate the mean concentration and concentration variance in the near field.The reason for the numerical efficiency of present particle-puff model is that it needs to track only thousands of particle-pairs in order to calculate the puff spread, while (the original) two-particle Lagrangian stochastic (LS) models need millions of particle-pairs to achieve statistically stable predictions.     

Time-dependent creep and shrinkage analysis of composite beams curved in-plan

This paper develops a numerical formulation for the time-dependent creep and shrinkage analysis of steel–concrete composite beams that are curved in-plan under conditions of service load. The creep behaviour of the concrete is considered by using the viscoelastic Wiechert model, in which the aging effect of the concrete is taken into account. The curved composite beam model that is developed also accounts for the partial shear interaction at the deck-girder interface in the tangential (or longitudinal) direction, as well as in the radial (or horizontal) direction, due to the flexibility of the shear connectors. Models based on the developed formulation are validated by comparisons with sophisticated and computationally intensive ABAQUS shell element models, and with available results reported in the literature. The effects of initial curvature and partial interaction on the time-dependent behaviour of curved composite beams are also illustrated in the examples.     

Manufacturing of composite parts reinforced through-thickness by tufting

The paper aims at providing practical guidelines for the manufacture of composite parts reinforced by tufting. The need for through-thickness reinforcement of high performance carbon fibre composite structures is reviewed and various options are presented. The tufting process is described in detail and relevant aspects of the technology are analysed such as: equipment configuration and setup, latest advances in tooling, thread selection, preform supporting systems and choice of ancillary materials. Effects of the process parameters on the preform fibre architecture and on the meso-structure of the reinforced component are discussed. Special emphasis is given to the different options available in terms of tuft insertion and loops management.Potential fields of application of the technology are investigated as well as the limitations of its applicability in relation to preform nature and geometry. Critical issues which may arise during the manufacturing process concerning thread insertion, loops formation, alteration to the fabric fibres layout or local volume fraction are identified.     

A composite model of macro-economic functioning of China

A composite model of macroeconomic variables was constructed to simulate the quantitative relationships among economic growth, money supply, and inflation, and to provide an evaluation tool for government economic decision-making. This model is a composite one in that it is combination of an Econometric Model and Neural Network Models. Simultaneous simulation of the composite model indicates that its accuracy is higher than a general Econometric Model. Results show that inflation had negative impact on money supply, and its impact on M2 is stronger than that on M1. Income and price elasticities of money supply bear the expected signs, and those of M2 are larger than those of M1, respectively. It also has been revealed that during the 1980 s inflation did not exert a significant impact on economic growth.     

A model for the metal deposition process

In IC industry, the manufacturing technology trends toward more precision and more miniaturization, such as from 28 to 14 nm process. This nano-manufacturing, metal deposition process must be studied to improve higher quality and more reliability production rate of produce. Hence, a model for the metal deposition process is necessary. This model of a vacuum metal film deposition system for substrate application with normal metal material is considered. In this model, the finite difference method is employed to discretize the solution domain into meshes and nodes. The numerical solution of electric potential or electric intensity of the metal film sputtering system can be obtained by MATLAB numerical simulation software, and to solve these equations of the discrete nodes. Numerical analysis results indicate that this simulation model can be employed to study the coating quality of the metal deposition process system.

     

Object-oriented methodology for intersection simulation model under heterogeneous traffic conditions

In developing countries like India, the traffic on roads is highly heterogeneous in nature, with vehicles of widely varying static and dynamic characteristics. In this type of traffic, vehicles do not follow lane discipline and they move freely over the entire width of roadway based on availability of space. To study this type of complex traffic flow and associated vehicular interactions, simulation is considered as an effective tool. An object-oriented methodology (OOM) for heterogeneous traffic simulation is proposed in this paper with focus on mid-block and intersection flow modeling. The paper presents the basics and advanced features of object-oriented programming (OOP) in detail in the context of traffic flow. The sample C++ code is discussed in detail to demonstrate the implementation of OOP features, such as encapsulation, inheritance and polymorphism. The contribution of this research work is the development of software objects for various components such as vehicle, traffic, link and node. This software can be adopted for heterogeneous traffic simulation programs, in general.