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Response Surface (response + surface)
Terms modified by Response Surface Selected AbstractsResponse Surfaces, Mixtures, and Ridge AnalysesJOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES A (STATISTICS IN SOCIETY), Issue 1 2008Philippe Castagliola No abstract is available for this article. [source] Tuning and control of dimensional consistency in molded productsADVANCES IN POLYMER TECHNOLOGY, Issue 3 2004David Kazmer Abstract Design and manufacturing of molded products are subject to uncontrolled variation (noise) and unknown performance behavior and/or requirements (uncertainty). The validity of current Six Sigma approaches for tolerancing and process optimization for multiple part dimensions is explored. Response surfaces for part weight and two part dimensions are developed as a function of multiple process variables for a rectangular part molded of isotactic polypropylene, i-PP. The process capabilities with respect to dimensional consistency and part weight are assessed using standard practices and Monte Carlo analysis. With respect to tuning of manufacturing processes, multicriteria optimization is necessary to ensure the selection of process set-points resulting in an acceptable likelihood of satisfying multiple dimensional specifications. The Extensive Simplex Method is shown to provide reasonable decision support for process optimization based on a linear process model derived from a main effects design of experiments. With respect to on-line quality control of dimensional consistency, part weight was validated as a good estimator of part dimensions, though requiring validation on an application by application basis. © 2004 Wiley Periodicals, Inc. Adv Polym Techn 23: 163,175, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20007 [source] Response surfaces for the combined effects of heat shock and smoke on germination of 16 species forming soil seed banks in south-east AustraliaAUSTRAL ECOLOGY, Issue 6 2007PAUL B. THOMAS Abstract There is limited understanding of how fire-related cues such as heat shock and smoke can combine to affect the germination response of seeds from fire-prone vegetation because combinations of multiple levels of both cues have rarely been investigated. Germination response surfaces were determined for the combination of heat shock and smoke by applying factorial combinations of temperature (up to 100°C) and aerosol smoke (0,20 min) to 16 species that form soil seed banks in the Sydney region of south-eastern Australia. Duplicate populations of three species were also examined to assess the constancy of a species response surface. Of the 19 populations examined, 16 showed a germination response to both the fire cues, which combined interactively in 14 populations, and independently in two. No population responded only to a single cue; however, seeds of 11 populations responded to heat in the absence of smoke, and nine responded to smoke in the absence of heat. Heat applied in the absence of smoke negatively affected germination in seven populations, either progressively as temperature increased, or above a set temperature. Negative germination responses over part of the temperature range were fully reversed at higher temperatures for unsmoked seeds of four populations (curvilinear heat response). Smoke effects were most frequently positive over all or part of the range of durations used, and when combined with heat frequently fully or partially reversed negative heat effects. Three populations required the obligatory combination of smoke and heat. A novel response to the cues was observed for three species, with smoke reversing negative heat effects at 75°C, being supplanted by a positive heat response of unsmoked seed at 100°C. The response surface for duplicate populations of two of the three species examined was variable. Heat shock and smoke frequently combined to affect germination, in both positive and negative ways. Consequently, to gain an accurate assessment of the response of seeds to fires, an experimental design that samples within the potential response zones of germination cues is essential. [source] High-solids biphasic CO2,H2O pretreatment of lignocellulosic biomassBIOTECHNOLOGY & BIOENGINEERING, Issue 3 2010Jeremy S. Luterbacher Abstract A high pressure (200,bar) CO2,H2O process was developed for pretreating lignocellulosic biomass at high-solid contents, while minimizing chemical inputs. Hardwood was pretreated at 20 and 40 (wt.%) solids. Switchgrass, corn stover, big bluestem, and mixed perennial grasses (a co-culture of big bluestem and switchgrass) were pretreated at 40 (wt.%) solids. Operating temperatures ranged from 150 to 250°C, and residence times from 20,s to 60,min. At these conditions a biphasic mixture of an H2O-rich liquid (hydrothermal) phase and a CO2 -rich supercritical phase coexist. Following pretreatment, samples were then enzymatically hydrolyzed. Total yields, defined as the fraction of the theoretical maximum, were determined for glucose, hemicellulose sugars, and two degradation products: furfural and 5-hydroxymethylfurfural. Response surfaces of yield as a function of temperature and residence time were compared for different moisture contents and biomass species. Pretreatment at 170°C for 60,min gave glucose yields of 77%, 73%, and 68% for 20 and 40 (wt.%) solids mixed hardwood and mixed perennial grasses, respectively. Pretreatment at 160°C for 60,min gave glucan to glucose yields of 81% for switchgrass and 85% for corn stover. Biotechnol. Bioeng. 2010;107: 451,460. © 2010 Wiley Periodicals, Inc. [source] A centroid-based sampling strategy for kriging global modeling and optimizationAICHE JOURNAL, Issue 1 2010Eddie Davis Abstract A new sampling strategy is presented for kriging-based global modeling. The strategy is used within a kriging/response surface (RSM) algorithm for solving NLP containing black-box models. Black-box models describe systems lacking the closed-form equations necessary for conventional gradient-based optimization. System optima can be alternatively found by building iteratively updated kriging models, and then refining local solutions using RSM. The application of the new sampling strategy results in accurate global model generation at lower sampling expense relative to a strategy using randomized and heuristic-based sampling for initial and subsequent model construction, respectively. The new strategy relies on construction of an initial kriging model built using sampling data obtained at the feasible region's convex polytope vertices and centroid. Updated models are constructed using additional sampling information obtained at Delaunay triangulation centroids. The new sampling algorithm is applied within the kriging-RSM framework to several numerical examples and case studies to demonstrate proof of concept. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] A PCA-based modelling technique for predicting environmental suitability for organisms from presence recordsDIVERSITY AND DISTRIBUTIONS, Issue 1-2 2001M. P. Robertson We present a correlative modelling technique that uses locality records (associated with species presence) and a set of predictor variables to produce a statistically justifiable probability response surface for a target species. The probability response surface indicates the suitability of each grid cell in a map for the target species in terms of the suite of predictor variables. The technique constructs a hyperspace for the target species using principal component axes derived from a principal components analysis performed on a training dataset. The training dataset comprises the values of the predictor variables associated with the localities where the species has been recorded as present. The origin of this hyperspace is taken to characterize the centre of the niche of the organism. All the localities (grid-cells) in the map region are then fitted into this hyperspace using the values of the predictor variables at these localities (the prediction dataset). The Euclidean distance from any locality to the origin of the hyperspace gives a measure of the ,centrality' of that locality in the hyperspace. These distances are used to derive probability values for each grid cell in the map region. The modelling technique was applied to bioclimatic data to predict bioclimatic suitability for three alien invasive plant species (Lantana camara L., Ricinus communis L. and Solanum mauritianum Scop.) in South Africa, Lesotho and Swaziland. The models were tested against independent test records by calculating area under the curve (AUC) values of receiver operator characteristic (ROC) curves and kappa statistics. There was good agreement between the models and the independent test records. The pre-processing of climatic variable data to reduce the deleterious effects of multicollinearity, and the use of stopping rules to prevent overfitting of the models are important aspects of the modelling process. [source] Integrative optimization by RBF network and particle swarm optimizationELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 12 2009Satoshi Kitayama Abstract This paper presents a method for the integrative optimization system. Recently, many methods for global optimization have been proposed. The objective of these methods is to find a global minimum of nonconvex function. However, large numbers of function evaluations are required, in general. We utilize the response surface method to approximate function space to reduce the function evaluations. The response surface method is constructed from sampling points. The RBF Network, which is one of the neural networks, is utilized to approximate the function space. Then Particle Swarm Optimization (PSO) is applied to the response surface. The proposed system consists of three parts: (Part 1) generation of the sampling points, (Part 2) construction of response surface by RBF Network, (Part 3) optimization by PSO. By iterating these three parts, it is expected that the approximate global minimum of nonconvex function can be obtained with a small number of function evaluations. Through numerical examples, the effectiveness and validity are examined. © 2009 Wiley Periodicals, Inc. Electron Comm Jpn, 92(12): 31,42, 2009; Published online in Wiley InterScience (www.interscience. wiley.com). DOI 10.1002/ecj.10187 [source] Variable smoothing in Bayesian intrinsic autoregressionsENVIRONMETRICS, Issue 8 2007Mark J. Brewer Abstract We introduce an adapted form of the Markov random field (MRF) for Bayesian spatial smoothing with small-area data. This new scheme allows the amount of smoothing to vary in different parts of a map by employing area-specific smoothing parameters, related to the variance of the MRF. We take an empirical Bayes approach, using variance information from a standard MRF analysis to provide prior information for the smoothing parameters of the adapted MRF. The scheme is shown to produce proper posterior distributions for a broad class of models. We test our method on both simulated and real data sets, and for the simulated data sets, the new scheme is found to improve modelling of both slowly-varying levels of smoothness and discontinuities in the response surface. Copyright © 2007 John Wiley & Sons, Ltd. [source] Surrogate model-based strategy for cryogenic cavitation model validation and sensitivity evaluationINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 9 2008Tushar Goel Abstract The study of cavitation dynamics in cryogenic environment has critical implications for the performance and safety of liquid rocket engines, but there is no established method to estimate cavitation-induced loads. To help develop such a computational capability, we employ a multiple-surrogate model-based approach to aid in the model validation and calibration process of a transport-based, homogeneous cryogenic cavitation model. We assess the role of empirical parameters in the cavitation model and uncertainties in material properties via global sensitivity analysis coupled with multiple surrogates including polynomial response surface, radial basis neural network, kriging, and a predicted residual sum of squares-based weighted average surrogate model. The global sensitivity analysis results indicate that the performance of cavitation model is more sensitive to the changes in model parameters than to uncertainties in material properties. Although the impact of uncertainty in temperature-dependent vapor pressure on the predictions seems significant, uncertainty in latent heat influences only temperature field. The influence of wall heat transfer on pressure load is insignificant. We find that slower onset of vapor condensation leads to deviation of the predictions from the experiments. The recalibrated model parameters rectify the importance of evaporation source terms, resulting in significant improvements in pressure predictions. The model parameters need to be adjusted for different fluids, but for a given fluid, they help capture the essential fluid physics with different geometry and operating conditions. Copyright © 2008 John Wiley & Sons, Ltd. [source] A new approach to response surface development for detailed gas-phase and surface reaction kinetic model optimizationINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 2 2004Scott G. Davis We propose a new method for constructing kinetic response surfaces used in the development and optimization of gas-phase and surface reaction kinetic models. The method, termed as the sensitivity analysis based (SAB) method, is based on a multivariate Taylor expansion of model response with respect to model parameters, neglecting terms higher than the second order. The expansion coefficients are obtained by a first-order local sensitivity analysis. Tests are made for gas-phase combustion reaction models. The results show that the response surface obtained with the SAB method is as accurate as the factorial design method traditionally used in reaction model optimization. The SAB method, however, presents significant computational savings compared to factorial design. The effect of including the partial and full third order terms was also examined and discussed. The SAB method is applied to optimization of a relatively complex surface reaction mechanism where large uncertainty in rate parameters exists. The example chosen is laser-induced fluorescence signal of OH desorption from a platinum foil in the water/oxygen reaction at low pressures. We introduce an iterative solution mapping and optimization approach for improved accuracy. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 36: 94,106, 2004 [source] Two-stage computing budget allocation approach for the response surface methodINTERNATIONAL TRANSACTIONS IN OPERATIONAL RESEARCH, Issue 6 2007J. Peng Abstract Response surface methodology (RSM) is one of the main statistical approaches to search for an input combination that optimizes the simulation output. In the early stages of RSM, an iterative steepest ascent search procedure is frequently used. In this paper, we attempt to improve this procedure by considering a more realistic case where there are computing budget constraints, and formulate a new computing budget allocation problem to look into the important issue of allocating computing budget to the design points in the local region of experimentation. We propose a two-stage computing budget allocation approach, which uses a limited budget to estimate the response surface in the first stage and then uses the rest of the budget to improve the lower bound of the estimated response at the center of the next design region in the second stage. Several numerical experiments are carried out to compare the two-stage approach with the regular factorial design, which allocates budget equally to each design point. The results show that our two-stage allocation outperforms the equal allocation, especially when the system noise is large. [source] Geographic patterns of diversity in streams are predicted by a multivariate model of disturbance and productivityJOURNAL OF ECOLOGY, Issue 3 2006BRADLEY J. CARDINALE Summary 1Univariate explanations of biodiversity have often failed to account for broad-scale patterns in species richness. As a result, increased attention has been paid to the development and testing of more synthetic multivariate hypotheses. One class of multivariate hypotheses, founded in successional diversity theory, predict that species richness is jointly influenced by periodic disturbances that create new niche opportunities in space or time, and the production of community biomass that speeds displacement of inferior by superior competitors. 2While the joint response of diversity to disturbance and productivity has gained support from theoretical and small-scale experimental studies, evidence that corresponding patterns of biodiversity occur broadly across natural systems is scarce. 3Using a data set that employed standardized methods to sample 85 streams throughout the mid-Atlantic United States of America, we show that biogeographical patterns of primary producer diversity in stream ecosystems are consistent with the predictions of a multivariate model that incorporates disturbance frequency and community biomass production as independent variables. Periphyton species richness is a concave-down function of disturbance frequency (mean no. floods year,1) and of biomass production (µg of biomass accrual cm,2 day,1), and an increasing function of their interaction. 4Changes in richness across the disturbance × productivity response surface can be related to several predicted life-history traits of the dominant species. 5Our findings complement prior studies by showing that multivariate models which consider interactive effects of community production and ecosystem disturbance are, in fact, candidate explanations of much broader patterns of richness in natural systems. Because multivariate models predict synergistic effects of ecological variables on species diversity, human activities , which are simultaneously altering both the disturbance regime and productivity of streams , could be influencing biodiversity more than previously anticipated. [source] OPTIMIZATION OF NATTOKINASE PRODUCTION CONDUCTION USING RESPONSE SURFACE METHODOLOGYJOURNAL OF FOOD PROCESS ENGINEERING, Issue 1 2006DJA-SHIN WANG ABSTRACT Natto has attracted worldwide attention because of its health benefits and long history in Japanese food. It has been found that a potent fibrinolytic enzyme named nattokinase, which is extracted from natto, is able to prevent atherosclerosis. The production of nattokinase may be influenced by various factors such as temperature, shaking speed, volume of medium, fermentation time and so forth. Three-step response surface methodology was applied to obtain the optimal operation conditions of the fermentation process in order to maximize the nattokinase yield. The three major steps are described as follows. First, the important factors for fermentation were identified by L8 orthogonal array experiment. The chosen factors were temperature (37 or 45C), shaking speed (110 or 150 rpm), volume of medium (80 or 120 mL), Brix of wheat bran extract (1.5 or 3°), Brix of soy meal extract (1 or 2°), glucose concentration (0.6 or 1.2%) and fermentation time (24 or 36 h). Second, a regression equation was established between the response (i.e., the enzyme activity) and the two statistically significant factors (i.e., the volume of medium and fermentation time). Third, the optimal solutions for the volume of medium and fermentation time were obtained based on the response surface of the regression equation. According to the response surface analysis, the optimal operation conditions for the fermentation process should be 80 mL and 37.0817 h for the volume of medium and the fermentation time, respectively, which resulted in 459.11 FU/mL as the predicted enzyme activity. [source] Influence of Storage Atmosphere and Temperature on Quality Evolution of Cut Belgian EndivesJOURNAL OF FOOD SCIENCE, Issue 8 2001M.D. Van de Velde ABSTRACT: An optimal combination of O2, CO2, and N2 for storage of cut Belgian Endive was defined, investigating visual quality aspects. In the experimental design, principles of mixture theory were used. The acceptability of cut endives stored under different gas combinations, selected in the range where both CO2 and O2 were varied between 2% and 18%, was evaluated by a consumer panel at different time intervals during storage. The response was modeled with a second-degree polynomial, the response surface pointed in the direction of a gas mixture 10% CO2, 10% O2, and 80% N2 for maximum acceptability or best quality during storage. Repeated experiments, including different varieties from 2 different growers, confirmed the optimal gas concentration, (10% CO2, 10% O2, and 80% N2). In a second step, the effect of temperature on quality degradation of cut endives stored under optimal atmosphere conditions, was quantified using the Arrhenius equation. An activation energy of 16.3 kcal/mol was obtained. [source] Attribute-based differentiation of alternativesJOURNAL OF MULTI CRITERIA DECISION ANALYSIS, Issue 6 2002Article first published online: 5 DEC 200, Jeffrey M. Keisler Abstract An intermediate step is introduced to the dialogue decision process for decision analysis. Alternatives are refined after they have been generated within a strategy table but before they are subject to more detailed evaluation. Two or more judges create a subjective mapping from alternatives to attributes that will later be mapped to criteria. In strategy tables, each of the alternative strategies consists of a coherent set of choices made across several decisions that are to be coordinated. These strategic alternatives are modified so as to increase their differentiation in the attribute space, rather than in the decision space alone. When criteria weights are unknown, the best alternative from the modified set may be superior to the best alternative from the original set. Furthermore, analysis of the resulting alternatives may yield a better mapping of the value response surface for the action space, in the sense that this mapping leads to eventual construction of a higher value alternative. Results are reported for a consulting engagement incorporating the proposed step. Copyright © 2003 John Wiley & Sons, Ltd. [source] Molecular Reproduction & Development: Volume 76, Issue 4MOLECULAR REPRODUCTION & DEVELOPMENT, Issue 4 2009Article first published online: 23 FEB 200 Computed cost function for in silico optimization of a cryoprotectant removal protocol. Karlsson et al. used membrane permeability data to predict the response of rhesus monkey oocytes to various methods for removing intracellular propylene glycol. The process parameter-space is shown as a gray plane; the corresponding response surface represents the expected cytotoxicity, and vertical surfaces (green and violet) demarcate predicted regimes of deleterious osmotic shock. See the accompanying article by Karlsson et al. in this issue. [source] Moisture sorption in moulded fibre trays and effect on static compression strengthPACKAGING TECHNOLOGY AND SCIENCE, Issue 4 2003Gitte Sørensen Abstract This study provides a basic understanding of moisture sorption in moulded fibre packaging for food at varying environmental temperatures and humidities, and the resultant effects on static compression strength. The Guggenheim,Anderson,de Boer (GAB) model is used successfully to construct moisture sorption isotherms in the range 2,25°C and 33,98% relative humidity (% r.h.) (R2 = 0.949,0.999), in which moisture content varies from 5.4 to 28.3,g/100,g dry fibre. Static compression strength (SCS) is substantially affected by changes in moisture content of moulded fibre and decreases exponentially with increasing moisture content. The results indicate a minor hysteresis effect on static compression strength. For adsorption of moisture, a relative strength measure, % SCS (experimental SCS in kg divided by a standard SCS in kg), is given by % SCS = 13.83 + 166.50,·,e,0.0978,m (m is moisture content). The temperature dependence of moisture adsorption is incorporated in the GAB model by relating GAB coefficients, m0 and C, exponentially to temperature, T. By combining this with the exponential model for % SCS, static compression strength can be predicted directly from the surrounding temperature and humidity. Illustrated in a response surface plot the effects of changes in the surroundings are simple and readily accessible, e.g. for packaging designers and sales people. It is noted that an increase in humidity from 50% r.h. to 95% r.h. at constant temperature results in a drastic reduction in % SCS from 100% to 40%, whereas the temperature effect is typically less than 10% SCS when reducing temperature from 25°C to 2°C. Copyright © 2003 John Wiley & Sons, Ltd. [source] Likelihood and bayesian approaches to inference for the stationary point of a quadratic response surfaceTHE CANADIAN JOURNAL OF STATISTICS, Issue 2 2008Valeria Sambucini Abstract In response surface analysis, a second order polynomial model is often used for inference on the stationary point of the response function. The standard confidence regions for the stationary point are due to Box & Hunter (1954). The authors propose an alternative parametrization, in which the stationary point is the parameter of interest; likelihood techniques and Bayesian analysis are then easier to perform. The authors also suggest an approximate method to get highest posterior density regions for the maximum point (not simply for the stationary point). Furthermore, they study the coverage probabilities of these Bayesian regions through simulations. Approches vraisemblantiste et bayésienne pour I'inference portant sur le point stationnaire d'une surface de réponse quadratique Résumé: Dans l'analyse des surfaces de réponse, un polyn,me du second degré est souvent utilisé pour l'inférence portant sur le point stationnaire de la fonction de réponse. Les régions de confiance standards pour le point stationnaire sont dues à Box & Hunter (1954). Les auteurs proposent une paramétrisation différente dans laquelle le point stationnaire est le paramètre d'intér,t; ceci facilite l'emploi des techniques de vraisemblance et l'analyse bayésienne. Les auteurs suggèrent aussi une façon d'approximer les régions de plus haute densité a posteriori pour le point maximum (et non seulement pour le point stationnaire). De plus, ils étudient les propriétés de couverture des régions bayésiennespar voie de simulation. [source] Response surfaces for the combined effects of heat shock and smoke on germination of 16 species forming soil seed banks in south-east AustraliaAUSTRAL ECOLOGY, Issue 6 2007PAUL B. THOMAS Abstract There is limited understanding of how fire-related cues such as heat shock and smoke can combine to affect the germination response of seeds from fire-prone vegetation because combinations of multiple levels of both cues have rarely been investigated. Germination response surfaces were determined for the combination of heat shock and smoke by applying factorial combinations of temperature (up to 100°C) and aerosol smoke (0,20 min) to 16 species that form soil seed banks in the Sydney region of south-eastern Australia. Duplicate populations of three species were also examined to assess the constancy of a species response surface. Of the 19 populations examined, 16 showed a germination response to both the fire cues, which combined interactively in 14 populations, and independently in two. No population responded only to a single cue; however, seeds of 11 populations responded to heat in the absence of smoke, and nine responded to smoke in the absence of heat. Heat applied in the absence of smoke negatively affected germination in seven populations, either progressively as temperature increased, or above a set temperature. Negative germination responses over part of the temperature range were fully reversed at higher temperatures for unsmoked seeds of four populations (curvilinear heat response). Smoke effects were most frequently positive over all or part of the range of durations used, and when combined with heat frequently fully or partially reversed negative heat effects. Three populations required the obligatory combination of smoke and heat. A novel response to the cues was observed for three species, with smoke reversing negative heat effects at 75°C, being supplanted by a positive heat response of unsmoked seed at 100°C. The response surface for duplicate populations of two of the three species examined was variable. Heat shock and smoke frequently combined to affect germination, in both positive and negative ways. Consequently, to gain an accurate assessment of the response of seeds to fires, an experimental design that samples within the potential response zones of germination cues is essential. [source] Optimization of a novel headspace,solid-phase microextraction,gas chromatographic method by means of a Doehlert uniform shell design for the analysis of trace level ethylene oxide residuals in sterilized medical devicesBIOMEDICAL CHROMATOGRAPHY, Issue 6 2009Michael P. DiCicco Abstract Medical devices sterilized by ethylene oxide (EtO) retain trace quantities of EtO residuals, which may irritate patients' tissue. Reliably quantifying trace level EtO residuals in small medical devices requires an extremely sensitive analytical method. In this research, a Doehlert uniform shell design was utilized in obtaining a response surface to optimize a novel headspace,solid-phase microextraction,gas chromatographic (HS-SPME-GC) method developed for analyzing trace levels of EtO residuals in sterilized medical devices, by evaluating sterilized, polymer-coated, drug-eluting cardiovascular stents. The effects of four independent experimental variables (HS-SPME desorption time, extraction temperature, GC inlet temperature and extraction time) on GC peak area response of EtO were investigated simultaneously and the most influential experimental variables determined were extraction temperature and GC inlet temperature, with the fitted model showing no evidence of lack-of-fit. The optimized HS-SPME-GC method demonstrated overall good linearity/linear range, accuracy, repeatability, reproducibility, absolute recovery and high sensitivity. This novel method was successfully applied to analysis of trace levels of EtO residuals in sterilized/aerated cardiovascular stents of various lengths and internal diameter, where, upon heating, trace EtO residuals fully volatilized into HS for extraction, thereby nullifying matrix effects. As an alternative, this novel HS-SPME-GC method can offer higher sensitivity compared with conventional headspace analyzer-based sampling. Copyright © 2009 John Wiley & Sons, Ltd. [source] Performance Measures for Selection of Metamodels to be Used in Simulation OptimizationDECISION SCIENCES, Issue 1 2002Anthony C. Keys ABSTRACT This paper points out the need for performance measures in the context of simulation optimization and suggests six such measures. Two of the measures are indications of absolute performance, whereas the other four are useful in assessing the relative performance of various candidate metamodels. The measures assess performance on three fronts: accuracy of placing optima in the correct location, fit to the response, and fit to the character of the surface (expressed in terms of the number of optima). Examples are given providing evidence of the measures' utility,one in a limited scenario deciding which of two competing metamodels to use as simulation optimization response surfaces vary, and the other in a scenario of a researcher developing a new, sequential optimization search procedure. [source] SECM Visualization of Spatial Variability of Enzyme-Polymer Spots.ELECTROANALYSIS, Issue 19-20 20062: Complex Interference Elimination by Means of Selection of Highest Sensitivity Sensor Substructures, Artificial Neural Networks Abstract Polymer spots with entrapped glucose oxidase were fabricated on glass surfaces and the localized enzymatic response was subsequently visualized using scanning electrochemical microscopy (SECM) in the generator,collector mode. SECM images were obtained under simultaneous variation of the concentration of glucose (0,6,mM) and ascorbic acid (0,200,,M), or, in a second set of experiments, of glucose (0,2,mM) and 2-deoxy- D(+)-glucose (0,4,mM). Aiming at the quantification of the mixture components discretization of the response surfaces of the overall enzyme/polymer spot into numerous spatially defined microsensor substructures was performed. Sensitivity of sensor substructures to measured analytes was calculated and patterns of variability in the data were analyzed before and after elimination of interferences using principal component analysis. Using artificial neural networks which were fed with the data provided by the sensor substructures showing highest sensitivity for glucose, glucose concentration could be calculated in solutions containing unknown amounts of ascorbic acid with a good accuracy (RMSE 0.17,mM). Using, as an input data set, measurements provided by sensing substructures showing highest sensitivity for ascorbic acid in combination with the response of the sensors showing highest dependence on the glucose concentration, the error of the ascorbic acid concentration calculation in solution containing the unknown amount of glucose was 10,,M. Similarly, prediction of the glucose concentration in the presence of 2-deoxy- D(+)-glucose was possible with a RMSE of 0.1,mM while the error of the calculation of 2-deoxy- D(+)-glucose concentrations in the presence of unknown concentrations of glucose was 0.36,mM. [source] EXPERIMENTAL EVIDENCE FOR MULTIVARIATE STABILIZING SEXUAL SELECTIONEVOLUTION, Issue 4 2005Robert Brooks Abstract Stabilizing selection is a fundamental concept in evolutionary biology. In the presence of a single intermediate optimum phenotype (fitness peak) on the fitness surface, stabilizing selection should cause the population to evolve toward such a peak. This prediction has seldom been tested, particularly for suites of correlated traits. The lack of tests for an evolutionary match between population means and adaptive peaks may be due, at least in part, to problems associated with empirically detecting multivariate stabilizing selection and with testing whether population means are at the peak of multivariate fitness surfaces. Here we show how canonical analysis of the fitness surface, combined with the estimation of confidence regions for stationary points on quadratic response surfaces, may be used to define multivariate stabilizing selection on a suite of traits and to establish whether natural populations reside on the multivariate peak. We manufactured artificial advertisement calls of the male cricket Teleogryllus commodus and played them back to females in laboratory phonotaxis trials to estimate the linear and nonlinear sexual selection that female phonotactic choice imposes on male call structure. Significant nonlinear selection on the major axes of the fitness surface was convex in nature and displayed an intermediate optimum, indicating multivariate stabilizing selection. The mean phenotypes of four independent samples of males, from the same population as the females used in phonotaxis trials, were within the 95% confidence region for the fitness peak. These experiments indicate that stabilizing sexual selection may play an important role in the evolution of male call properties in natural populations of T. commodus. [source] Effects of cryptic mortality and the hidden costs of using length limits in fishery managementFISH AND FISHERIES, Issue 3 2007Lewis G Coggins Jr Abstract Fishery collapses cause substantial economic and ecological harm, but common management actions often fail to prevent overfishing. Minimum length limits are perhaps the most common fishing regulation used in both commercial and recreational fisheries, but their conservation benefits can be influenced by discard mortality of fish caught and released below the legal length. We constructed a computer model to evaluate how discard mortality could influence the conservation utility of minimum length regulations. We evaluated policy performance across two disparate fish life-history types: short-lived high-productivity (SLHP) and long-lived low-productivity (LLLP) species. For the life-history types, fishing mortality rates and minimum length limits that we examined, length limits alone generally failed to achieve sustainability when discard mortality rate exceeded about 0.2 for SLHP species and 0.05 for LLLP species. At these levels of discard mortality, reductions in overall fishing mortality (e.g. lower fishing effort) were required to prevent recruitment overfishing if fishing mortality was high. Similarly, relatively low discard mortality rates (>0.05) rendered maximum yield unobtainable and caused a substantial shift in the shape of the yield response surfaces. An analysis of fishery efficiency showed that length limits caused the simulated fisheries to be much less efficient, potentially exposing the target species and ecosystem to increased negative effects of the fishing process. Our findings suggest that for overexploited fisheries with moderate-to-high discard mortality rates, reductions in fishing mortality will be required to meet management goals. Resource managers should carefully consider impacts of cryptic mortality sources (e.g. discard mortality) on fishery sustainability, especially in recreational fisheries where release rates are high and effort is increasing in many areas of the world. [source] Joint full-waveform analysis of off-ground zero-offset ground penetrating radar and electromagnetic induction synthetic data for estimating soil electrical propertiesGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 3 2010D. Moghadas SUMMARY A joint analysis of full-waveform information content in ground penetrating radar (GPR) and electromagnetic induction (EMI) synthetic data was investigated to reconstruct the electrical properties of multilayered media. The GPR and EMI systems operate in zero-offset, off-ground mode and are designed using vector network analyser technology. The inverse problem is formulated in the least-squares sense. We compared four approaches for GPR and EMI data fusion. The two first techniques consisted of defining a single objective function, applying different weighting methods. As a first approach, we weighted the EMI and GPR data using the inverse of the data variance. The ideal point method was also employed as a second weighting scenario. The third approach is the naive Bayesian method and the fourth technique corresponds to GPR,EMI and EMI,GPR sequential inversions. Synthetic GPR and EMI data were generated for the particular case of a two-layered medium. Analysis of the objective function response surfaces from the two first approaches demonstrated the benefit of combining the two sources of information. However, due to the variations of the GPR and EMI model sensitivities with respect to the medium electrical properties, the formulation of an optimal objective function based on the weighting methods is not straightforward. While the Bayesian method relies on assumptions with respect to the statistical distribution of the parameters, it may constitute a relevant alternative for GPR and EMI data fusion. Sequential inversions of different configurations for a two layered medium show that in the case of high conductivity or permittivity for the first layer, the inversion scheme can not fully retrieve the soil hydrogeophysical parameters. But in the case of low permittivity and conductivity for the first layer, GPR,EMI inversion provides proper estimation of values compared to the EMI,GPR inversion. [source] Multi-objective turbomachinery optimization using a gradient-enhanced multi-layer perceptronINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 6 2009M. C. Duta Abstract Response surface models (RSMs) have found widespread use to reduce the overall computational cost of turbomachinery blading design optimization. Recent developments have seen the successful use of gradient information alongside sampled response values in building accurate response surfaces. This paper describes the use of gradients to enhance the performance of the RSM provided by a multi-layer perceptron. Gradient information is included in the perceptron by modifying the error function such that the perceptron is trained to fit the gradients as well as the response values. As a consequence, the back-propagation scheme that assists the training is also changed. The paper formulates the gradient-enhanced multi-layer perceptron using algebraic notation, with an emphasis on the ease of use and efficiency of computer code implementation. To illustrate the benefit of using gradient information, the enhanced neural network model is used in a multi-objective transonic fan blade optimization exercise of engineering relevance. Copyright © 2008 John Wiley & Sons, Ltd. [source] EXTRUSION COOKING OF BLENDS OF SOY FLOUR AND SWEET POTATO FLOUR ON SPECIFIC MECHANICAL ENERGY (SME), EXTRUDATE TEMPERATURE AND TORQUEJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 4 2001M. O. IWE Defatted soy flour and sweet potato flour containing 18% moisture were mixed in a pilot mixer, and extruded in an Almex-Bettenfeld single-screw extruder operated at varying rotational speed and die diameter. A central composite, rotatable nearly orthogonal design, which required 23 experiments for three factors (feed composition (fc), screw speed (ss) and die diameter (dd)) was developed and used for the generation of response surfaces. Effects of the extrusion variables on specific mechanical energy (SME), extrudate temperature (ET), and torque (T) were evaluated using response surface analysis. Results showed that product temperature increased with increases in die diameter, screw speed and feed composition. However, the effect of die diameter was greater than those of screw speed and feed composition. Decrease in die diameter with increase in sweet potato content increased torque. Screw speed exhibited a linear effect on torque. [source] COLOR and CHLOROPHYLL CONTENT CHANGES of MINIMALLY PROCESSED KIWIFRUITJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 1 2000MARÍA ASUNCIÓN LEUNDA A combined factors preservation technology involving blanching and vacuum solutes (sucrose, potassium sorbate, ascorbic and citric acids, zinc chloride) impregnation was proposed to minimize color changes in minimally processed kiwifruit slices during one month storage. Atmospheric impregnation was also studied in order to compare both impregnation techniques. A Box-Behnken design was adopted and second order polynomial models were computed for different storage times to relate some process variables (blanching time, zinc content, storage temperature) to a color function (Brown Index). As the storage time increased, the response surfaces for vacuum treated fruits were vertically displaced to greater Brown Index values while the response surface behavior for atmospheric impregnated fruits were less dependent on storage time. For vacuum treated fruits, combinations of blanching and addition of zinc chloride improved the color of the finished product at all storage temperatures assayed, but these treatments were detrimental for atmospheric impregnated fruits, increasing significantly the Brown Index values. After storage, total chlorophyll had been degraded between 70 and 90% depending on the pretreatments. There did not appear to be any consistent relation between the changes which occurred in the total chlorophyll content and color. [source] Relationship between leaf emergence and optimum spray timing for leaf blotch (Rhynchosporium secalis) control on winter barleyPLANT PATHOLOGY, Issue 3 2006C. S. Young For wheat, the optimum time to apply fungicide to control disease on a given leaf layer is usually at, or shortly after, full leaf emergence. Data from field experiments on barley were used to investigate whether the same relationship was applicable to control of leaf blotch on barley. Replicated plots of winter barley were sown in the autumns of 1991, 1992 and 1993 at sites in southwest England with high risk of Rhynchosporium secalis infection. Single fungicide treatments at four doses (0·25, 0·5, 0·75 or 1·0 times the label rate) were applied at one of eight different spray times, starting in mid-March in each year, with intervals of 10,11 days between spray timings. Disease was assessed every 10,11 days and area under the disease progress curve (AUDPC) values were used to construct fungicide dose by spray time response surfaces for each of the upper four leaves, for each year. Spray timings shortly before leaf emergence were found to minimize the AUDPC for each year and leaf layer, and also the effective dose (the dose required to achieve a specified level of control), similar to wheat. Fungicide treatments on barley were effective for a longer period before leaf emergence than afterwards, probably because treatments before emergence of the target leaf reduced inoculum production on leaves below. This partly explains why fungicides tend to be applied earlier in the growth of barley compared with wheat. [source] Predicting effective fungicide doses through observation of leaf emergencePLANT PATHOLOGY, Issue 6 2000N. D. Paveley Experimental data were used to test the hypothesis that the effective fungicide dose (ED) , the dose required to achieve a given level of disease suppression , varies in a predictable manner according to the pattern of development of the wheat canopy. Replicated and randomized field plots received a single systemic fungicide spray at either zero (control), 0·25, 0·5, 0·75 or 1·0 dose (the recommended dose), at one of eight timings from April to June. Wheat cultivars and locations for experiments were selected to promote epidemics of septoria tritici spot and yellow rust caused by Septoria tritici (anamorph of Mycosphaerella graminicola) and Puccinia striiformis, respectively. Logistic or exponential disease progress curves were fitted to disease severity data and used to estimate the date of disease onset (t0) and relative epidemic growth rate (r) on each leaf layer for each treatment. Area under the disease progress curve (AUDPC) values were used to construct fungicide dose by spray timing response surfaces for each of the upper four leaves. A parsimonious function, with an exponential form in the dose,response dimension and a normal distribution in the timing dimension described a high proportion of the variation in AUDPC (R2 values ranging from 0·73 to 0·97). Consistent patterns of treatment effect were noted across pathogen species, leaf layers, sites and seasons. Fungicide applications that coincided with full leaf emergence delayed t0 on that leaf layer. Treatments applied after full leaf emergence did not delay t0, but reduced r. Progressively earlier or later treatments, or lower doses, had decreasing effects. AUDPC was affected more by t0 than r. AUDPC response surface parameter estimates showed that curvature of the dose,response was not affected by spray timing, but appeared to be a characteristic of the fungicide,pathogen combination. However, the lower asymptote of the dose,response curve, and hence the ED, varied substantially with spray timing. The pattern of change in ED with spray timing was consistent across a range of leaf layers, pathosystems and seasons, and the spray timing at which the ED was minimized varied only within a small range, around the time of leaf emergence. In contrast, variation in untreated disease severity, resulting from variation in initial inoculum and weather, was large. It was concluded that the main value of disease forecasting schemes may be in their capacity to predict the level of untreated disease, to which the economic optimum, or ,appropriate', dose relates. Spray timing determines the part of the canopy where disease will be efficiently controlled and hence the green leaf area saved. Timing decisions should relate to observations of emergence of those leaf layers important to yield. [source] | |||||||||||||||||||||||||