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Robustness Analysis (robustness + analysis)

Distribution by Scientific Domains
Business, Economics, Finance and Accounting44%

Selected Abstracts

Robustness Analysis of the Escherichiacoli Metabolic Network

BIOTECHNOLOGY PROGRESS, Issue 6 2000
Jeremy S. Edwards
Genomic, biochemical, and strain-specific data can be assembled to define an in silico representation of the metabolic network for a select group of single cellular organisms. Flux-balance analysis and phenotypic phase planes derived therefrom have been developed and applied to analyze the metabolic capabilities and characteristics of Escherichia coli K-12. These analyses have shown the existence of seven essential reactions in the central metabolic pathways (glycolysis, pentose phosphate pathway, tricarboxylic acid cycle) for the growth in glucose minimal media. The corresponding seven gene products can be grouped into three categories: (1) pentose phosphate pathway genes, (2) three-carbon glycolytic genes, and (3) tricarboxylic acid cycle genes. Here we develop a procedure that calculates the sensitivity of optimal cellular growth to altered flux levels of these essential gene products. The results indicate that the E. coli metabolic network is robust with respect to the flux levels of these enzymes. The metabolic flux in the transketolase and the tricarboxylic acid cycle reactions can be reduced to 15% and 19%, respectively, of the optimal value without significantly influencing the optimal growth flux. The metabolic network also exhibited robustness with respect to the ribose-5-phosphate isomerase, and the ribose-5-phosephate isomerase flux was reduced to 28% of the optimal value without significantly effecting the optimal growth flux. The metabolic network exhibited limited robustness to the three-carbon glycolytic fluxes both increased and decreased. The development presented another dimension to the use of FBA to study the capabilities of metabolic networks. [source]

Robustness analysis of flexible structures: practical algorithms

INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 8 2003
Gilles Ferreres
Abstract When analysing the robustness properties of a flexible system, the classical solution, which consists of computing lower and upper bounds of the structured singular value (s.s.v.) at each point of a frequency gridding, appears unreliable. This paper describes two algorithms, based on the same technical result: the first one directly computes an upper bound of the maximal s.s.v. over a frequency interval, while the second one eliminates frequency intervals, inside which the s.s.v. is guaranteed to be below a given value. Various strategies are then proposed, which combine these two techniques, and also integrate methods for computing a lower bound of the s.s.v. The computational efficiency of the scheme is illustrated on a real-world application, namely a telescope mock-up which is significant of a high order flexible system. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Which Economic Freedoms Contribute to Growth?

KYKLOS INTERNATIONAL REVIEW OF SOCIAL SCIENCES, Issue 3 2002
A Comment
Most studies on the relationship between economic freedom and growth employ a measure of economic freedom based on an (ad hoc) aggregation of various underlying components. We argue that the alternative aggregation procedure as recently suggested by Heckelman and Stroup (2000) , in which aggregation is directly based upon the relevance of each component for growth, as determined by multivariate regression analysis , is seriously flawed. We present an alternative index based on latent variable estimation techniques. Using standard robustness analyses we find that this index of economic freedom is not robustly related to economic growth. [source]

Optimal fuzzy reasoning and its robustness analysis

INTERNATIONAL JOURNAL OF INTELLIGENT SYSTEMS, Issue 11 2004
Lei Zhang
Fuzzy reasoning methods are extensively used in intelligent systems and fuzzy control. Most existing fuzzy reasoning methods follow rules of logical inference. In this article, fuzzy reasoning is treated as an optimization problem. The idea of optimal fuzzy reasoning is reviewed and three new optimal fuzzy reasoning methods are given by using new optimization objective functions. The robustness of fuzzy reasoning, that is, how errors in premises affect conclusions in fuzzy reasoning, is evaluated in a probabilistic or statistical context by using the Monte Carlo simulation method. Six optimal fuzzy reasoning methods are evaluated in comparison with the CRI method in terms of probabilistic robustness. © 2004 Wiley Periodicals, Inc. Int J Int Syst 19: 1033,1049, 2004. [source]

Robust MIMO disturbance observer analysis and design with application to active car steering

INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 8 2010
Bilin Aksun Güvenç
Abstract A multi-input,multi-output extension of the well-known two control degrees-of-freedom disturbance observer architecture that decouples the problem into single-input,single-output disturbance observer loops is presented in this paper. Robust design based on mapping D -stability and the frequency domain specifications of weighted sensitivity minimization and phase margin bound to a chosen controller parameter space is presented as a part of the proposed design approach. The effect of the choice of disturbance observer Q filter on performance is explained with a numerical example. This is followed by the use of structured singular values in the robustness analysis of disturbance observer controlled systems subject to structured, real parametric and mixed uncertainty in the plant. A design and simulation study based on a four wheel active car steering control example is used to illustrate the methods presented in the paper. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Robust ,2 -gain feedforward control of uncertain systems using dynamic IQCs

INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 11 2009
I. E. Köse
Abstract We consider the problem of robust ,2 -gain disturbance feedforward control for uncertain systems described in the standard LFT form. We use integral quadratic constraints (IQCs) for describing the uncertainty blocks in the system. For technical reasons related to the feedforward problem, throughout the paper, we work with the duals of the constraints involved in robustness analysis using IQCs. We obtain a convex solution to the problem using a state-space characterization of nominal stability that we have developed recently. Specifically, our solution consists of LMI conditions for the existence of a feedforward controller that guarantees a given ,2 -gain for the closed-loop system. We demonstrate the effectiveness of using dynamic IQCs in robust feedforward design through a numerical example. Copyright © 2008 John Wiley & Sons, Ltd. [source]

The effects of technology shocks on hours and output: a robustness analysis

JOURNAL OF APPLIED ECONOMETRICS, Issue 5 2010
Fabio Canova
We analyze the effects of neutral and investment-specific technology shocks on hours and output. Long cycles in hours are removed in a variety of ways. Hours robustly fall in response to neutral shocks and robustly increase in response to investment-specific shocks. The percentage of the variance of hours (output) explained by neutral shocks is small (large); the opposite is true for investment-specific shocks. ,News shocks' are uncorrelated with the estimated technology shocks. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Quantifying uncertainty using robustness analysis in the application of ORESTE to sewer rehabilitation projects prioritization,Brussels case study

JOURNAL OF MULTI CRITERIA DECISION ANALYSIS, Issue 3-4 2009
Eliseo Ana Jr
Abstract Sewer systems are considered extremely important components of the urban water infrastructure due to their function and capital-intensive nature. These systems, however, have been undergoing aging and deterioration, thus needing repair or rehabilitation. Historically, the budgets for sewer rehabilitation are often scarce and too limited to address the requirements, requiring utility managers to prioritize the competing projects. In this paper, the application of ORESTE to the prioritization of sewer rehabilitation projects for the Brussels, Belgium network was demonstrated. The 43 proposed projects were ranked based on a set of 16 criteria. In addition, a methodology was introduced to investigate the robustness of the ORESTE solution. The inclusion of the robustness analysis into the technique allowed for the quantification of the uncertainties associated with the priority rankings. This type of information is very important in developing confidence among decision makers as to their decision on the priority ranking of sewer rehabilitation projects. Copyright © 2010 John Wiley & Sons, Ltd. [source]