A new model for hyperelasticity

The essential criterion for a good mathematical model for hyperelasticity is its ability to match the measured strain energy curves under different deformations over a large range. One group of models for hyperelasticity is to express the strain energy as a function of I ₁, I ₂, I ₃, the invariants of the right Cauchy-Green deformation tensor. Under the assumption of incompressibility, it can be proved that all valid (I ₁, I ₂) pairs fall in a region bounded by the I ₁ – I ₂ locus from deformations under simple extension and equal-biaxial extension (or, equivalently, simple compression). I ₁ – I ₂ locus from planar extension lies inside the region. Since the strain energy curves from simple deformation modes can be measured from experiments, it is possible to approximately obtain the strain energy under other (I ₁, I ₂) values by interpolating data from the three measured curves. The proposed model for hyperelasticity is an interpolation algorithm with all mathematical details. The new model is implemented into a user-defined material subroutine in commercial FEA software. It can not only accurately reproduce the measured data from these simple deformation modes but also predict the stress–strain curve under planar extension in a reasonable good accuracy even without using the measured data from planar extension.     

A new method for workshop real time scheduling

Workshop real time scheduling is one of the key factors in improving manufacturing system efficiency. This is especially true for workshops in which various products are processed simultaneously, and use multipurpose machines. Real time scheduling is appropriate to handle perturbations in the environment of the manufacturing process, a major issue at the shop floor level. The products to be processed have release times and due dates and the resources are multipurpose machines. A decision support system for real time scheduling is described. It is based on an original approach, aiming at searching for characteristics of a set of schedules compatible with the main manufacturing constraints to be satisfied. This set of schedules is obtained by defining sequences of groups of permutable operations for every resource. A method to find such a set is described. We emphasize the use of this group sequence as a decision support system. Significant states and events requiring real time decisions are identified and three main types of decisions are analysed. For each of them, the proposed decision support system is detailed and explained.     

A new model for public-private partnerships

In the United States, federal technology transfer programs, public-private initiatives, national centers for technology and manufacturing, research and development consortia, and university outreach centers have all been developed as public-investment-based solutions to enhancing economic competitiveness. Each of these activities has problems and shortcomings associated with it. In lieu of these traditional programs, an expanded, integrated, and self-sufficient model for public-private partnerships is proposed through which 503(c) nonprofit organizations can manage and operate technology extension programs for the state or federal government. This approach addresses small, medium, and large business in an integrated fashion in terms of nine sectors of economic competitiveness. Methods for acquiring and utilizing technology and accessing government markets are proposed. A unique method for obtaining self-sufficiency and growth is developed. The presented model leverages federal investments into an independent and self-sufficient, privately-funded partnership. This type of entrepreneurial approach to public-private initiatives has been conspicuously absent from the majority of existing federal and state funded technology programs. It is expected that this model will lead to a higher rate of return on public investment.     

关于多孔材料的新模型

指出了多孔材料的经典性模型-Gibson-Ashby模型的不足,如孔隙单元非密积、棱柱状态不等价等,提出了一个能弥补Gibson-Ashby模型这些不足的新模型．应用这个新模型,可获得与实验结果符合良好的三维网状泡沫材料电阻率关系和力学关系的表征．实验结果证明,应用于多孔材料时,由新模型所得的有关数理关系明显优于Gibson-Ashby模型。     

A discrete time reactive scheduling model for new order insertion in job shop,make-to-order industries

This research presents a new reactive scheduling methodology for job shop, make-to-order industries. An integer linear programming formulation previously developed by the authors to schedule these types of industries is extended to address the problem of inserting new orders in a predetermined schedule, which is important in order-driven industries. A reactive scheduling algorithm is introduced to iteratively update the schedules. Numerical results on realistic examples of job shops of different sizes illustrate the effectiveness of the approach. In each case, different alternatives for inserting a set of new orders in an initial schedule are optimally generated, enabling the user to choose the most convenient one. Solutions are characterised by measures of scheduling efficiency as well as stability measures that assess the impact of rescheduling operations in a previously defined scheduling solution.     

Estimation of homogenisation time for superalloys based on a new diffusional model

The inter-diffusion of segregating elements (Nb, Mo, and Ti) in the cast ingot of Inconel 718 superalloy during homogenisation at elevated temperature was studied by a new model based on the characteristic diffusion length. The proposed simple method was used for obtaining the homogenisation time required for back-diffusion of each element. Therefore, the developed model can be used for both studying the diffusion of alloying elements and estimation of homogenisation time, where the latter is important from the industrial standpoint.     

A new application of an improved DRBEM model for water wave propagation over a frictional uneven bottom

This paper presents a numerical scheme to approximate water wave diffraction, refraction and frictional dissipation over an axi-symmetric pit. Based on an improved extended mild-slope equation (EMSE) including bottom friction effect, as the elliptic governing differential equation, dual reciprocity boundary element method (DRBEM) is employed to model water wave propagation over an axi-symmetric pit. To the authors' knowledge, this is the first application of DRBEM for water wave scattering over a pit. In order to promote accuracy of the model, not only effects of the bottom curvature and the slope-squared terms which are neglected in the mild-slope equation (MSE), are considered, but also effect of the bottom friction is measured by the improved EMSE. Numerical results are compared with existing analytical or numerical solutions or with experimental data by several examples. Through these numerical experiments reliability and efficiency of present DRBEM model for determining the total wave field over an uneven bottom is approved.     

A new damage model for composite laminates

Aircraft composite structures must have high stiffness and strength with low weight, which can guarantee the increase of the pay-load for airplanes without losing airworthiness. However, the mechanical behavior of composite laminates is very complex due the inherent anisotropy and heterogeneity. Many researchers have developed different failure progressive analyses and damage models in order to predict the complex failure mechanisms. This work presents a damage model and progressive failure analysis that requires simple experimental tests and that achieves good accuracy. Firstly, the paper explains damage initiation and propagation criteria and a procedure to identify the material parameters. In the second stage, the model was implemented as a UMAT (User Material Subroutine), which is linked to finite element software, ABAQUS™, in order to predict the composite structures behavior. Afterwards, some case studies, mainly off-axis coupons under tensile or compression loads, with different types of stacking sequence were analyzed using the proposed material model. Finally, the computational results were compared to the experimental results, verifying the capability of the damage model in order to predict the composite structure behavior.     

A Stackelberg-Nash model for new product design

Existing conjoint approaches to optimal new product design have focused on the Nash equilibrium concept to model competitive reactions. Whereas these approaches have treated all competing firms equally as Nash players, one firm may have an advantage over its rivals, e.g., more pre-experience on competitors’ behavior and/or a first-mover advantage. This paper proposes a Stackelberg-Nash (leader-followers) model which can accomodate such information for decision making. The optimal product design problem is formulated from the perspective of a profit-maximizing new entrant (the leader) who wants to launch a brand onto an existing product market and acts with foresight by anticipating price-design reactions of the incumbent firms (the Nash followers). In the absence of closed-form solutions, we use a sequential iterative procedure to compute a Stackelberg-Nash equilibrium and to establish its uniqueness. The new conjoint model is illustrated under several competitive scenarios and price, design and profit implications are compared to a simple Nash equilibrium model. We find that a Stackelberg leader strategy may not only yield a much higher profit for the new entrant than a Nash strategy, but may also lead to strong profit asymmetries between competitors with still higher profits for the incumbent firms. In other words, the incumbent firms may also benefit strongly from a new entrant choosing a Stackelberg leader strategy.     

模糊推理算法的一种新模型

根据全蕴涵三I模糊推理算法的思想,讨论基于左连续伪三角范数x1y=0,0≤x≤a,0≤y≤b min(x,y),x>a或y>b诱导的剩余蕴涵的三I算法,分别给出基于这个左连续伪三角范数诱导的第一蕴涵算子与第二蕴涵算子的FMP-算法与FMT-算法,并给出FMP-解与FMT-解的具体表达式.将模糊推理算法与左连续伪三角范数结合起来,为解决实际应用问题提供模糊推理算法的一种新的模型.     

A new model for non-Gaussian random excitations

Very often one is called upon to model time series data which are clearly non-Gaussian, but which retain some aspects of a Gaussian process. In the present paper, a novel methodology which helps in modelling such data is presented. The method is essentially to express the process as a series with finite number of terms, wherein the first term is a Gaussian process with zero mean and unit standard deviation. Non-Gaussian higher order correction terms are added to this such that each succeeding term is orthogonal or uncorrelated with all the previous terms. The unknown coefficients in the series representation can be expressed in terms of the estimated moments of the data. Further the autocorrelation or PSD of the data can be exactly reproduced by the non-Gaussian model. The use of the proposed model is illustrated by considering the unevenness data of railway tracks. Application to response of systems under non-Gaussian excitation is also briefly discussed.     

A new stochastic model for crack propagation

In the following paper we present a new model for crack propagation. The new model is able to involve sudden growth of crack length (jumps) and is a generalization of the well-known Paris–Erdogen law. We obtain the lifetime distribution and the residual lifetime distributions.     

A new hysteresis model for steel members

Since it is not economical to design structures to respond to earthquake loads in their elastic range, dissipation of energy by post‐elastic deformation has been recommended. This requires an understanding of the hysteretic behaviour of structural members. A mathematical model is proposed for the hysteretic response of steel members. The model is based on a pre‐defined skeleton curve, and consists of a linear and a non‐linear region. The linear region is twice the elastic length on the skeleton curve, while the non‐linear region is formed by superimposing an elliptical dissipation function on the skeleton curve. The shape of the proposed dissipation function and the hysteretic loops are compared with experimental results. Good agreement has been noted. Furthermore, it is shown that stiffness degradation can be easily incorporated in the model. While the model can currently by used in the analysis of accumulated damages for steel structures, it has the potential to be extended to reinforced concrete structures, as well. Copyright © 1999 John Wiley & Sons, Ltd.     

A new skeletal model for fabric drapes

Fabric drapes are typical large displacement, large rotation and small strain problems. Compared with continuum shell finite element methods, methods that skeletonize the fabric sheet into a set of interconnected nodes appear to be more popular in drape problems with extensive wrinkles. These skeletal methods may resort to particle mechanics and formulate the elastic energy or the equations of motion in terms of the node-to-node distance and the angles between the straight lines joining adjacent nodes. Alternatively, beam elements can be employed to skeletonize the fabric sheet at the expense of using rotational in addition to translational nodal DOFs. In this paper, a new skeletal model based on the small strain and curvature assumptions is devised. In contrast to most, if not all, skeletal models for fabric drape simulation, all the stretching, shearing and bending energies in the model are simple polynomials of the grid-point␣displacement. Fabric drape problems with extensive wrinkles are examined. The presence of sharp fold, seam and cut in the undeformed fabric sheet as well as fabric-to-solid contact are considered. The predicted appearances are pleasant and conform to real life observations.     

A model with nonzero rise time for AE signals

Acoustic emission (AE) signals are conventionally modelled as damped or decaying sinusoidal functions. A major drawback of this model is its negligible or zero rise time. This paper proposes an alternative model, which provides for the rising part of the signal without sacrificing the analytical tractability and simplicity of the conventional model. Signals obtained from the proposed model through computer programs are illustrated for demonstrating their parity with actual AE signals. Analytic expressions for the time-domain parameters, viz., peak amplitude and rise time used in conventional AE signal analysis, are also derived. The model is believed to be also of use in modelling the output signal of any transducer that has finite rise time and fall time.     

一种新的双耳时间差模型的特性分析

1引言双耳时间差(Interaural Time Difference,简称ITD)是指声源发出的声波到双耳的传输时间差。ITD是低频声源定位的主要因素,它对双耳听觉的     

Four-stream solution for atmospheric radiative transfer over a non-Lambertian surface

An analytical model characterizing the atmospheric radiance field over a non-Lambertian surface divides the radiation field into three components: unscattered radiance, single-scattering radiance, and multiple-scattering radiance. The first two components are calculated exactly. A δ-four-stream approximation is extended to calculate the azimuth-independent multiple-scattering radiance over a non-Lambertian surface, which is modeled by a statistical bidirectional reflectance distribution function (BRDF). Accuracy is assessed with respect to the exact results computed from a Gauss-Seidel iterative algorithm. Experiments comparing the results obtained with Lambertian and non-Lambertian surfaces show that incorporating the BRDF into the four-stream approximation significantly improves the accuracy in calculating radiance as well as radiative flux.     

A model equation for steady surface waves over a bump

The objective of this paper is to study the solutions of a model equation for steady surface waves on an ideal fluid over a semicircular or semielliptical bump. For upstream Froude number F>1, we show that the numerical solution of the equation has two branches and there is a cut-off value of F below which no solution exists. For F<1, the problem is reformulated to overcome the so-called infinite-mass dilemma. A branch of solutions and a cut-off value of F, above which no solution exists, are found. Furthermore, we also obtain a branch of hydraulic-fall solutions which decrease monotonically from upstream to downstream.