Sensitivity importance‐based robust optimization of structures with incomplete probabilistic information

Robust design optimization (RDO) is usually performed by minimizing the nominal value of a performance function and its dispersion considering equal importance to each individual gradient of the performance function. However, it is well known that all gradients are not equally important. An efficient sensitivity importance‐based RDO technique is proposed in the present study for optimum design of structures characterized by bounded uncertain input parameters. The basic idea of the proposed RDO formulation is to improve the robustness of a performance function by using a new gradient index that utilizes the importance factors proportional to the importance of the gradients of the performance function. The same concept is also extended to the constraints. To enhance the robustness of the constraints, the constraint functions are also modified by using the importance factor proportional to the importance of the associated gradient of the constraint. Because all the variables are not equally important to capture the presence of uncertainty, an improved robust solution is obtained by the proposed approach compared with the conventional RDO approach. The present formulation is illustrated with the help of three informative examples. The results are compared with the conventional RDO results to study the effectiveness of the proposed RDO approach. Copyright © 2012 John Wiley & Sons, Ltd.     

Intra mode decision and frame layer Lagrange multiplier adjustment scheme for H.264 based on structural similarity

H.264 takes rate distortion optimisation (RDO) technique to perform intra and inter mode decision and achieves higher coding efficiency, but the objective distortion metric such as mean square error (MSE) is employed in traditional RDO framework, which cannot acquire optimal subjective quality. In this paper, structural similarity (SSIM)-based subjective distortion is applied to RDO-based intra mode decision in H.264 I frame video coding, and a linear SSIM distortion model is firstly proposed and SSIM-based rate distortion cost function for intra mode decision is defined. Furthermore, a content adaptive frame layer Lagrange multiplier adjustment scheme is proposed to balance the tradeoff between rate and SSIM distortion better. Experimental results show that, the proposed method encodes image structural information more effectively and thus acquires better perceptual quality and subjective RDO performance compared with objective distortion-based RDO method. Under the same perceptual quality, our scheme achieves about 8·03% I frame bit rate reduction on average for various sequences over MSE-based RDO employed in JM reference software.     

Robust design optimization of nonlinear energy sink under random system parameters

Generally, in designing nonlinear energy sink (NES), only uncertainties in the ground motion parameters are considered and the unconditional expected mean of the performance metric is minimized. However, such an approach has two major limitations. First, ignoring the uncertainties in the system parameters can result in an inefficient design of the NES. Second, only minimizing the unconditional mean of the performance metric may result in large variance of the response because of the uncertainties in the system parameters. To address these issues, we focus on robust design optimization (RDO) of NES under uncertain system and hazard parameters. The RDO is solved as a bi-objective optimization problem where the mean and the standard deviation of the performance metric are simultaneously minimized. This bi-objective optimization problem has been converted into a single objective problem by using the weighted sum method. However, solving an RDO problem can be computationally expensive. We thus used a novel machine learning technique, referred to as the hybrid polynomial correlated function expansion (H-PCFE), for solving the RDO problem in an efficient manner. Moreover, we adopt an adaptive framework where H-PCFE models trained at previous iterations are reused and hence, the computational cost is less. We illustrate that H-PCFE is computationally efficient and accurate as compared to other similar methods available in the literature. A numerical study showcasing the importance of incorporating the uncertain system parameters into the optimization procedure is shown. Using the same example, we also illustrate the importance of solving an RDO problem for NES design. Overall, considering the uncertainties in the parameters have resulted in a more efficient design. Determining NES parameters by solving an RDO problem results in a less sensitive design.     

Sequential approximate robust design optimization using radial basis function network

This paper proposes a sequential approximate robust design optimization (SARDO) with the radial basis function (RBF) network. In RDO, the mean and the standard deviation of objective should be minimized simultaneously. Therefore, the RDO is generally formulated as bi-objective design optimization. Our goal is to find a robust optimal solution with a small number of function evaluations, not identifying a set of Pareto-optimal solution using Multi-Objective Evolutionary Algorithms. The weighted sum is often used to find a robust optimal solution. In contrast, the weighted lp norm method is used in this paper. Through illustrative examples, some validations of the weighted lp norm method to the RDO are clarified. Next, SARDO with the RBF network is discussed. In general, the standard deviation of functions is obtained by using the finite difference method. Thus, in order to obtain the standard deviation of functions, the finite difference method is directly applied to the response surface. High accuracy of the finite difference method will leads to highly accurate robust optimal solution. In order to avoid the inaccurate numerical calculation, the standard deviation is expressed by only the Gaussian kernel. As the result, it is expected that a highly accurate robust optimal solution can be found with a small number of function evaluations. Through numerical examples, the validity of the proposed approach is examined. Finally, the variable blank holder force trajectory for reducing springback is examined.     

Optimal design of composite shells based on minimum weight and maximum feasibility robustness

A robust design optimization (RDO) approach for minimum weight and safe shell composite structures with minimal variability into design constraints under uncertainties is proposed. A new concept of feasibility robustness associated to the variability of design constraints is considered. So, the feasibility robustness is defined through the determinant of variance–covariance matrix of constraint functions introducing in this way the joint effects of the uncertainty propagations on structural response. A new framework considering aleatory uncertainty into RDO of composite structures is proposed. So, three classes of variables and parameters are identified: deterministic design variables, random design variables and random parameters. The bi-objective optimization search is performed using on a new approach based on two levels of dominance denoted by Co-Dominance-based Genetic Algorithm (CoDGA). The use of evolutionary concepts together sensitivity analysis based on adjoint variable method is a new proposal. The examples with different sources of uncertainty show that the Pareto front definition depends on random design variables and/or random parameters considered in RDO. Furthermore, the importance to control the uncertainties on the feasibility of constraints is demonstrated. CoDGA approach is a powerfully tool to help designers to make decision establishing the priorities between performance and robustness.     

Comparison of deoxidation capability on the specific surface area of irregular titanium powder using calcium reductant

Irregular titanium powders of various particle size in the range 60–250?μm were deoxidized using calcium as the reductant, and the effect of specific surface area on the process was investigated. At 1273?K, the oxygen concentration was reduced from 0.2840?wt% to 0.0950?wt%, from 0.2050?wt% to 0.0825?wt%, and from 0.1700?wt% to 0.0825?wt% in titanium powders with average particle sizes of 60?μm, 125?μm, and 250?μm, respectively, and the corresponding removal degree of oxygen (RDO) for these specimens was determined to be 66.5%, 59.7%, and 51.4%; that is, the RDO was inversely proportional to the average particle size of the irregular titanium powder. It was confirmed that the specific surface area of the titanium powder available for reaction with calcium, was the critical factor in the deoxidation of titanium powder using calcium as reductant.     

JPEG2000的一种编码前码率分配算法

针对JPEG2000推荐的码率分配算法导致的计算冗余多、编码速度慢并且编码缓存大的不足,本文提出一种编码前最优分配码率的方法以提高JPEG2000的编码速度.该方法通过对小波系数失真模型的率失真理论分析,得出在总码率限制的情况下,使得总体视觉加权失真最小的最佳码率分配准则,并根据该准则给出可实现的码率分配算法.实验表明,该方法可以实现精确有效的编码前码率预分配,做到了"所编即所需",加速了JPEG2000编码,满足高速编码和低缓存需求的要求.     

Multiresponse optimization using multivariate process capability index

Robust design is an efficient method for product and process improvement which combines experimentation with optimization to create a system that is less sensitive to uncontrollable variation. In this article, a simple and integrated modeling methodology for robust design is proposed. This methodology achieves the robustness objective function and input variables constraints simultaneously. The objective function is written in terms of the multivariate process capability vector (MC_pm) of several competing features of the system under study. The proposed methodology is applicable to general functions of the system performance with random variables. The effectiveness of the methodology is verified using two real‐world examples which are compared with those of other robust design methods. Copyright © 2010 John Wiley & Sons, Ltd.     

Lipid compositions and French registered designations of origins of virgin olive oils predicted by chemometric analysis of mid-infrared spectra

The combination of mid-infrared (MIR) spectroscopy with multivariate analysis provides an original approach to study the profile of virgin olive oils (VOOs) in relation to composition and geographical origin. Chemometric treatment of mid-infrared spectra (n=402) is assessed for quantification of fatty acids (14 components) and triacylglycerols (19 components) in VOO samples and for classification into six very geographically closed registered designations of origin (RDOs) of French VOO ("Aix-en-Provence", "Haute-Provence", "Vallée des Baux de Provence", "Nice", "N?mes", and "Nyons"). Spectroscopic interpretation of regression vectors has shown that each RDO is correlated to one specific component of VOO according to their cultivar compositions. The results are satisfactory, in spite of the similarity of cultivar compositions between two denominations of origin ("Aix-en-Provence" and "Vallée des Baux de Provence"). Chemometric treatment of MIR spectra makes it possible to obtain similar results to those obtained by time-consuming analytical techniques such as gas chromatography (GC) and high-performance liquid chromatography (HPLC) and constitutes a fast and robust tool for authentication of these French VOOs.     

Multiaxial notch fatigue life prediction based on pseudo stress correction and finite element analysis under variable amplitude loading

A new computational methodology is proposed for fatigue life prediction of notched components subjected to variable amplitude multiaxial loading. In the proposed methodology, an estimation method of non‐proportionality factor (F) proposed by authors in the case of constant amplitude multiaxial loading is extended and applied to variable amplitude multiaxial loading by using Wang‐Brown's reversal counting approach. The pseudo stress correction method integrated with linear elastic finite element analysis is utilized to calculate the local elastic‐plastic stress and strain responses at the notch root. For whole local strain history, the plane with weight‐averaged maximum shear strain range is defined as the critical plane in this study. Based on the defined critical plane, a multiaxial fatigue damage model combined with Miner's linear cumulative damage law is used to predict fatigue life. The experimentally obtained fatigue data for 7050‐T7451 aluminium alloy notched shaft specimens under constant and variable amplitude multiaxial loadings are used to verify the proposed methodology and equivalent strain‐based methodology. The results show that the proposed methodology is superior to equivalent strain‐based methodology.     

基于切氏软系统方法论的产品情感化设计

目的 利用切氏软系统方法论研究产品的情感化设计,为未来的用户体验提供有益参考。方法 首先对切氏软系统方法论进行分析研究,总结切氏软系统方法论的应用思路,继而依照此应用思路,逐层剖析产品设计中的“情感化”软问题,从而利用切氏软系统方法论为产品情感化设计搭建合理的概念模型,并比较基于此概念模型的产品实例与现状。结果 验证了此概念模型的合理性与普适性,以及印证了产品情感化设计的重要性与必要性。结论 一方面,切氏软系统方法论是以人类活动系统为核心展开的系统理论;另一方面,情感化设计也正是在以用户为中心基础上衍生出的概念,基于这一共通点,利用切氏软系统方法论构建的概念模型对产品进行情感化设计具有合乎逻辑的实际意义。     

Calibration of Expert Judgments Applied to Uncertainty Assessment

Abstract:

This article contributes a methodology for eliciting expert judgment in support of decision analysis associated with the conceptual design of advanced engineering systems. To provide a basis for decision making in the presence of model and input parameter uncertainties, experts in several disciplines can be utilized to provide model parameter estimates to facilitate analyses. The judgment elicitation methodology was developed to cover a multitude of system disciplines using multiple experts. To address consistency in expert assessments, the methodology includes expert assessment calibration means. A sample application of the resultant expert judgment methodology is discussed. An engineering manager can use the methodology described in this article to assess viability of potential courses of action in high-risk or advanced state-of-the-art technology systems development ventures.     

Functional tolerancing: A design for manufacturing methodology

The problem addressed in this paper is the development of a physico-mathematical basis for mechanical tolerances. The lack of such a basis has fostered a decoupling of design (function) and manufacturing. The groundwork for a tolerancing methodology is laid by a model of profile errors, whose components are justified by physical reasoning and estimated using mathematical tools. The methodology is then presented as an evolutionary procedure that harnesses the various tools, as required, toanalyze profiles in terms of a minimum set of profile parameters and tore-generate them from the parameters. This equips the designer with a rational means for estimating performance prior to manufacturing, hence integrating design and manufacturing. The utility of thefunctional tolerancing methodology is demonstrated with performance simulations of a lathe-head-stock design, focusing on gear transmission with synthesized errors.     

A bibliometric tool to assess the regional dimension of university–industry research collaborations

The present study proposes a bibliometric methodology for measuring the grade of correspondence between regional industry’s demand for research collaboration and supply from public laboratories. The methodology also permits measurement of the intensity and direction of the regional flows of knowledge in public–private collaborations. The aim is to provide a diagnostic instrument for regional and national policy makers, which could add to existing ones to plan interventions for re-balancing sectorial public supply of knowledge with industrial absorptive capacity, and maximizing appropriability of knowledge spillovers. The methodology is applied to university–industry collaborations in the hard sciences in all Italian administrative regions.     

Sustainable packaging design: a holistic methodology for packaging design

This study describes a holistic methodology for sustainable packaging design. This methodology studies the combined systems of packaging and the packaged products across the whole distribution chain from manufacturer to end consumer and the life cycle from raw material extraction to the waste phase. It contains a number of indicators that are grouped into the following main categories: environmental sustainability, distribution costs, product protection, market acceptance and user friendliness. The methodology integrates a number of different analytical methods. It is intended to be used in packaging design and optimisation, for idea generation, decision support and as documentation of properties of existing packaging systems. The study describes experiences with the methodology from one case study in the Norwegian Food Industry. The experiences show that the methodology is very comprehensive, and gives a good overview of the properties of a packaging solution. It enables quantitative comparisons between different packaging solutions throughout the design process. The methodology reduces the risk of implementing sub‐optimal packaging solutions. An additional benefit of the methodology is gained by working in cross‐functional teams. One potential drawback is that the methodology can be resource and data intensive. The methodology can be used as a tool box in packaging design, i.e. it is not necessary to use all methods and quantify all indicators to gain benefit. However, all indicators and requirements should be evaluated and considered. In all cases, it should be considered to include additional indicators if important sustainability issues have not been addressed. Copyright © 2010 John Wiley & Sons, Ltd.     

DRG cost weight volatility and hospital performance

We develop a robust methodology which estimates the consequences of DRG cost weight volatility on hospital performance. The methodology is first developed using the hospital baserate as quantitative measure of hospital performance, then analyzed theoretically in the more general framework of cost-benefit analysis, and finally applied to two groups of hospitals. The first data set consists of a homogeneous group of 21 maximum-care hospitals in Germany and incorporates approximately 936,000 inpatient cases in 2003. The second data set consists of a heterogeneous group of 97 German hospitals and incorporates approximately 896,000 inpatient cases in 2003. The main finding is that the robust cost-benefit methodology developed in this study leads to results that are consistent with the theoretical background, since the hospital baserate spread in the more homogeneous group of hospitals is clearly lower than in the more heterogeneous group of hospitals. Our methodology illustrates the robustness of a hospital’s performance with respect to DRG cost weight changes and, therefore, represents a helpful tool in discussions about hospital budgets, strategic alliances, mergers, etc.     

Computable exact bounds for linear outputs from stabilized solutions of the advection–diffusion–reaction equation

The paper introduces a methodology to compute strict upper and lower bounds for linear‐functional outputs of the exact solutions of the advection–diffusion–reaction equation. The bounds are computed using implicit a posteriori error estimators from stabilized finite element approximations of the exact solution. The new methodology extends the a posteriori error estimates yielding bounds for the standard Galerkin formulation to be able to obtain bounds for stabilized formulations. This methodology is combined with both hybrid‐flux and flux‐free techniques for error assessment. The application to stabilized formulations provides sharper estimates than when applied to Galerkin methods. The best results are found in combination with the flux‐free technique. Copyright © 2012 John Wiley & Sons, Ltd.     

Australian developments in the analysis of composite structures with material and geometric nonlinearities

To achieve the potential cost savings resulting from the use of composites in ‘primary’ structural components, i.e. wing fuselage skins, it is important that composite structures be used outside the linear regime. However, before this can be achieved a computational methodology capable of analysing the detailed local stress states in conditions where there are both geometrically and material nonlinearities is necessary. This paper presents one such approach in which the ‘global structure’ is modelled by employing plate-type finite elements and the local details are modelled with solid 3D finite elements. A coupling techniques based on multi-point constraints is then employed to connect the 2D and local 3D models. The approach presented allows for significant changes in finite element mesh density and enables the connection of very detailed local models with less detailed global models. To illustrate this analysis methodology a range of nonlinear structural problems involving both geometrical and material nonlinearities are considered. The methodology is first validated by considering a plate bending and a post-buckling problem for which the solutions were known. The methodology is then used to analyse the post-buckling response of both a shear and an axially loaded composite stringer/skin panel. In both cases the computed results correlated very well with experimental results. The results from these test cases suggest that the proposed analysis methodology provides a viable computational tool for determining the local 3D stress states for structures undergoing complex nonlinear deformation states.     

Two‐level multiscale enrichment methodology for modeling of heterogeneous plates

A new two‐level multiscale enrichment methodology for analysis of heterogeneous plates is presented. The enrichments are applied in the displacement and strain levels: the displacement field of a Reissner–Mindlin plate is enriched using the multiscale enrichment functions based on the partition of unity principle; the strain field is enriched using the mathematical homogenization theory. The proposed methodology is implemented for linear and failure analysis of brittle heterogeneous plates. The eigendeformation‐based model reduction approach is employed to efficiently evaluate the non‐linear processes in case of failure. The capabilities of the proposed methodology are verified against direct three‐dimensional finite element models with full resolution of the microstructure. Copyright © 2009 John Wiley & Sons, Ltd.