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Response Surface Designs (response + surface_design)

Distribution by Scientific Domains

Mathematics and Statistics	33%

Selected Abstracts

Cost-constrained G -efficient Response Surface Designs for Cuboidal Regions

QUALITY AND RELIABILITY ENGINEERING INTERNATIONAL, Issue 2 2006
Youjin Park
Abstract In many industrial experiments there are restrictions on the resource (or cost) required for performing the runs in a response surface design. This will require practitioners to choose some subset of the candidate set of experimental runs. The appropriate selection of design points under resource constraints is an important aspect of multi-factor experimentation. A well-planned experiment should consist of factor-level combinations selected such that the resulting design will have desirable statistical properties but the resource constraints should not be violated or the experimental cost should be minimized. The resulting designs are referred to as cost-efficient designs. We use a genetic algorithm for constructing cost-constrained G -efficient second-order response surface designs over cuboidal regions when an experimental cost at a certain factor level is high and a resource constraint exists. Consideration of practical resource (or cost) restrictions and different cost structures will provide valuable information for planning effective and economical experiments when optimizing statistical design properties. Copyright © 2005 John Wiley & Sons, Ltd. [source]

A Genetic Algorithm Hybrid for Constructing Optimal Response Surface Designs

QUALITY AND RELIABILITY ENGINEERING INTERNATIONAL, Issue 7 2004
David Drain
Abstract Hybrid heuristic optimization methods can discover efficient experiment designs in situations where traditional designs cannot be applied, exchange methods are ineffective, and simple heuristics like simulated annealing fail to find good solutions. One such heuristic hybrid is GASA (genetic algorithm,simulated annealing), developed to take advantage of the exploratory power of the genetic algorithm, while utilizing the local optimum exploitive properties of simulated annealing. The successful application of this method is demonstrated in a difficult design problem with multiple optimization criteria in an irregularly shaped design region. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Response Surface Designs for Experiments in Bioprocessing

BIOMETRICS, Issue 2 2006
Steven G. Gilmour
Summary Many processes in the biological industries are studied using response surface methodology. The use of biological materials, however, means that run-to-run variation is typically much greater than that in many experiments in mechanical or chemical engineering and so the designs used require greater replication. The data analysis which is performed may involve some variable selection, as well as fitting polynomial response surface models. This implies that designs should allow the parameters of the model to be estimated nearly orthogonally. A class of three-level response surface designs is introduced which allows all except the quadratic parameters to be estimated orthogonally, as well as having a number of other useful properties. These subset designs are obtained by using two-level factorial designs in subsets of the factors, with the other factors being held at their middle level. This allows their properties to be easily explored. Replacing some of the two-level designs with fractional replicates broadens the class of useful designs, especially with five or more factors, and sometimes incomplete subsets can be used. It is very simple to include a few two- and four-level factors in these designs by excluding subsets with these factors at the middle level. Subset designs can be easily modified to include factors with five or more levels by allowing a different pair of levels to be used in different subsets. [source]

Cost-constrained G -efficient Response Surface Designs for Cuboidal Regions

Lipase-Catalyzed Acyl Exchange of Soybean Phosphatidylcholine in n -Hexane: A Critical Evaluation of Both Acyl Incorporation and Product Recovery

BIOTECHNOLOGY PROGRESS, Issue 2 2005
Anders F. Vikbjerg
Lipase-catalyzed acidolysis was examined for the production of structured phospholipids in a hexane system. In a practical operation of the reaction system, the formation of lyso-phospholipids from hydrolysis is often a serious problem, as demonstrated from previous studies. A clear elucidation of the issue and optimization of the system are essential for the practical applications in reality. The effects of enzyme dosage, reaction temperature, solvent amount, reaction time, and substrate ratio were optimized in terms of the acyl incorporation, which led to the products, and lyso-phospholipids formed by hydrolysis, which led to the low yields. The biocatalyst used was the commercial immobilized lipase Lipozyme TL IM and substrates used were phosphatidylcholine (PC) from soybean and caprylic acid. A response surface design was used to evaluate the influence of selected parameters and their relationships on the incorporation of caprylic acid and the corresponding recovery of PC. Incorporation of fatty acids increased with increasing enzyme dosage, reaction temperature, solvent amount, reaction time, and substrate ratio. Enzyme dosage had the most significant effect on the incorporation, followed by reaction time, reaction temperature, solvent amount, and substrate ratio. However the parameters had also a negative influence on the PC recovery. Solvent amount had the most negative effect on recovery, followed by enzyme dosage, temperature, and reaction time. Individually substrate ratio had no significant effect on the PC recovery. Interactions were observed between different parameters. On the basis of the models, the reaction was optimized for the maximum incorporation and maximum PC recovery. With all of the considerations, the optimal conditions are recommended as enzyme dosage 29%, reaction time 50 h, temperature 54 °C, substrate ratio 15 mol/mol caprylic acid/PC, and 5 mL of hexane per 3 g substrate. No additional water is necessary. Under these conditions, an incorporation of caprylic acid up to 46% and recovery of PC up to 60% can be obtained from the prediction. The prediction was confirmed from the verification experiments. [source]

A mouse model of lupin allergy

CLINICAL & EXPERIMENTAL ALLERGY, Issue 8 2009
N. E. Vinje
Summary Background Lupin has been introduced as a new food ingredient in an increasing number of European countries, resulting in reports of allergic reactions mostly due to cross-reactions in peanut-allergic individuals. Some cases of primary lupin allergy have also been reported. Objective The aim of our study was to develop a food allergy model of lupin in mice with anaphylaxis as the endpoint and further, to develop an approach to estimate the allergen dose inducing maximal sensitization using a statistical design requiring a limited number of animals. Methods Mice were immunized by intragastric gavage using cholera toxin as an adjuvant. A two-compartment response surface design with IgE as the main variable was used to estimate the maximal sensitizing dose of lupin in the model. This estimated dose was further used to evaluate the model. The mice were challenged with a high dose of lupin and signs of an anaphylactic reaction were observed. Antibody reactions (IgE and IgG2a), serum mast cell protease [mouse mast cell protease-1 (MMCP-1)] and ex vivo production of cytokines (IL-4, IL-5 and IFN-,) by spleen cells were measured. An immunoblot with regard to IgE binding was also performed. Results The dose that elicited the maximal sensitization measured as IgE was 5.7 mg lupin protein per immunization. Mice that received this dose developed anaphylactic reactions upon challenge, IgE against several proteins in the lupin extract, and high levels of MMCP-1, and showed a general shift towards a T-helper type 2 response. Post-challenge serum MMCP-1 levels corresponded to the seriousness of the anaphylactic reactions. Conclusion We have established a mouse model with clinical symptoms of lupin allergy, with an optimized dose of lupin protein. A statistical design that can be used to determine an optimal immunization dose with the use of a minimum of laboratory animals is described. [source]

Virtual Experiments and Their Use in Teaching Experimental Design

INTERNATIONAL STATISTICAL REVIEW, Issue 3 2007
Paul L. Darius
Summary The ability to design experiments in an appropriate and efficient way is an important skill, but students typically have little opportunity to get that experience. Most textbooks introduce standard general-purpose designs, and then proceed with the analysis of data already collected. In this paper we explore a tool for gaining design experience: computer-based virtual experiments. These are software environments which mimic a real situation of interest and invite the user to collect data to answer a research question. Two prototype environments are described. The first one is suitable for a course that deals with screening or response surface designs, the second one allows experimenting with block and row-column designs. They are parts of a collection we developed called ENV2EXP, and can be freely used over the web. We also describe our experience in using them in several courses over the last few years. [source]