University of North Florida
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Stuart Chalk, Ph.D.
Department of Chemistry
University of North Florida
Phone: 1-904-620-1938
Fax: 1-904-620-3535
Email: schalk@unf.edu
Website: @unf

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Powell

Classification: Signal processing -> Powell

Citations 11

"Application Of Artificial Neural Networks Coupled With An Orthogonal Design And Optimization Algorithms To Multifactor Optimization Of A New FIA System For The Determination Of Uranium(VI) In Ore Samples"
Analyst 2000 Volume 125, Issue 5 Pages 921-925
Sun Gang, Zhou Yongyao, Wang Huaiwen, Chen Hongli, Chen Xingguo and Hu Zhide

Abstract: A sensitive and selective spectrophotometric flow injection method has been developed for the determination of uranium(VI) in ore samples, based on the reaction of uranium(VI) with p-acetylchlorophosphonazo (CPA-pA) in a HNO3 medium. Most of the interfering ions were effectively eliminated by the masking reagent, diethyleneaminepentaacetic acid (DTPA). Artificial neural networks coupled with an orthogonal design and penalty algorithm were applied to the modeling of the proposed flow injection system and optimization of the experimental conditions. An orthogonal design was utilized to design the experimental protocol, in which three variables were varied simultaneously. ANNs with a faster back propagation (BP) algorithm were used to model the system. Optimum experimental conditions were generated automatically by using jointly ANNs and optimization algorithms in terms of sensitivity and sampling rate. In the U(VI)-CPA-pA system, Beers law was obeyed in the range 1.0-23.0 µg mL-1, the detection limit for uranium(VI) was 0.3 µg mL-1 and the sampling rate was 100 h-1. The method was applied to the determination of uranium(VI) in ore samples with satisfactory results. It was shown that this method had advantages over traditional methods in respect of improvement in the ability of optimization and reduction in analysis time.

"Application Of Natural Computation Techniques To Optimal Design Of Flow Injection Systems"
Anal. Chim. Acta 1999 Volume 402, Issue 1-2 Pages 275-283
J. de Gracia, A. Araujo, J. L. F. C. Lima, I. Villaescusa and M. Poch

Abstract: Row injection (FI) systems are widely used for online monitoring of chemical processes. Several approaches have been made in order to achieve the optimal design of the FI system, mainly based on the approach of deterministic models that describe the process using the mass balances around the system and the corresponding kinetic relations. Although, good results have been obtained with this approach, the complexity of the system and the effort necessary to calculate the parameters that characterize the FI system using a deterministic model, have led to the consideration of more empirical approaches to obtain a model of the process. In this paper, the authors present the results obtained in the application of two techniques, known as natural intelligence techniques, in the optimal design of a flow injection sandwich system for glucose and glycerol analysis. The optimization is performed using a genetic algorithm, in which a population evolves combining the genetic code of the most capable individuals of the previous generation. To evaluate the performance of each individual an artificial neural network is used. The results obtained with this approach are comparable with the one previously developed using a deterministic description of the FT system.

"Computer-assisted Qualimetric Optimization Of Analytical Methods"
Chemom. Intell. Lab. Syst. 1999 Volume 48, Issue 1 Pages 81-90
E. Vereda-Alonso, J. A. Pérez-Hidalgo, A. Ríos and M. Valcárcel

Abstract: Software that implements the SIMPLEX optimization method and the quality requirements of laboratories working on various tasks was developed. The program presents the users with different optimum experimental conditions according to preselected quality criteria, these variables being subsequently subjected to robustness test. This methodology is based on the development of a special response function from the area of a polygon constructed from four main variables, viz, sensitivity, precision, cost and throughput, each of which is weighted by a quality coefficient. In this way, the principal parameters that define overall analytical quality are integrated and weighted in order to obtain information on the quality parameters on which the quality policy of a given laboratory relies. The system was used to optimise the flow injection method for the determination of furfural with aniline. The results obtained are discussed, and the design of the apparatus and software is commented on.

"Comparison Of The Powell And Simplex Methods In The Optimization Of Flow Injection Systems - Simulation On Modelled Experimental Surfaces And Experimental Optimizations"
Anal. Chim. Acta 1990 Volume 241, Issue 1 Pages 31-42
M. del Valle, M. Poch, J. Alonso and J. Bartroli

Abstract: In the determination of NH3 by the indophenol reaction, both methods provided optimum conditions. However, the Powell algorithm needed fewer evaluations for the determination of maximum sensitivity and throughput and was efficient at the beginning of the process, needing the modification of only one independent variable. With the optimized system, the limit of detection was 5 ng mL-1 and the coefficient of variation (n = 32) for 3 µg mL-1 was 1.5% (throughput 70 per h). The calibration range covered 0.03 to 6 µg mL-1.
Ammonia Spectrophotometry

"An Integrated Design Strategy For Flow Injection Analysis Based On The Coupling Of Mathematical Modeling And Optimization Algorithms"
Anal. Chim. Acta 1995 Volume 310, Issue 2 Pages 289-296
A. Araújo, J. L. F. C. Lima, J. Gracia, M. Poch, J. Alonso*, J. Bartrolí and M. Del Valle

Abstract: A methodology to design a flow injection system with optimized performance characteristics was presented based on coupling a descriptive mathematical model to an optimization algorithm. The method was applied to the sequential determination of glucose and glycerol in a flow injection system using the sandwich technique. The axially dispersed plug flow model was coupled with Powell's optimization algorithm to generate a complete set of flow injection configuration, each of them optimized with respect to its objective function (better sensitivity, highest sampling rate, better resolution, etc.). The user selects the configuration which suits the requirements of the particular application.
Glucose Glycerol

"Real-time Simplex Optimization Of Flow Injection Systems For Chemical Analysis"
Anal. Chim. Acta 1998 Volume 366, Issue 1-3 Pages 313-318
Maria Fernanda Giné*, Robinson L. Tuon, André A. Cesta, Ana Paula Packer and Boaventura F. Reis

Abstract: A computer controlled flow injection system was assembled to implement a real-time simplex algorithm. Two experimental variables, flow rate and sample:reagent ratio were controlled by a fully automated manifold. A computer interface was programmed to command the pumping speed, introduction of sample:reagent amounts by solenoid valves, on-time data acquisition, and examn. of detector responses for application of the simplex algorithm. The feasibility of the approach was assessed by optimizing the flow parameters for Cl- determination in water with different analyte concentrations Optimum experimental conditions for 5.00, 25.0, 50.0, and 100 mg/L Cl- were maintained. A precision characterized by a relative standard deviation <1% and a sample throughput of 120/h were attained.
Chloride Water Spectrophotometry

"Comparison Of The Simplex And Powell Methods With A Weighted Response Function For The Optimization Of FIA Systems"
Talanta 1993 Volume 40, Issue 7 Pages 1113-1126
L. M. B. C. &Aacute;lvares-Ribeiro and A. A. S. C. Machado*J. Alonso, J. Bartroli and M. del Valle,

Abstract: The cited optimization methods were compared with regard to the determination of nitrite in water by flow injection spectrophotometry based on the method of Nakashima et al, (Anal. Chim. Acta, 1974, 155, 263). Both methods proved to be effective for the optimization, neither having any definite advantages over the other. The use of a weighted response function in the optimization methods was useful in assessing the versatility of flow injection systems.
Nitrite Water

"An ISFET-FIA System For High-precision PH Recording"
Sens. Actuat. B 1993 Volume 15, Issue 1-3 Pages 68-74
P. Woias, S. Koch and E. M&uuml;ller, D. Barrow and J. Cefai, G. Curtis and H. Hughes

Abstract: A description is given of a differential ISFET/REFET (reference FET) pH measurement system for use in continuous-flow analysis or FIA. The system involves differential sensing between two ISFET with identical gate insulator compositions; this permits effective suppression of common mode disturbances, including drift, without requiring the use of a glass reference electrode. The sensor was tested in an isolated rat liver perfusion system (Powell et al., Drug Metab. Drug Interact., 1989, 7, 53). Continuous inline measurements were also made of the pH of bile from anaesthetized rats. Resolution in both instances was typically 0.01 pH and detection of rapid changes in pH was possible. A stable and accurate readout could be obtained at the low flow rates involved.
pH Electrode Field effect transistor

"Combining Mathematical Modelling And The Powell Algorithm For The Optimization Of Flow Injection Sandwich Systems"
Analusis 1992 Volume 20, Issue 6 Pages 319-324
Poch, M.;Montesinos, J.L.;Del Valle, M.;Alonso, J.;Araujo, A.N.;Lima, J.L.F.C.

Abstract: In the sandwich procedure, the sample plug is situated between two reagent solution; diffusion at the two interfaces can be used to determine two species, provided that the configuration is optimized. The Powell algorithm is an iterative method in which an initial unidirectional search is made, e.g., up or down a range of values of a given parameter of the system. The initial search then defines a new direction of search and the process is repeated until convergence occurs. This algorithm was applied to the optimization of the injection volume, flow rate and mixing-coil length. A mathematical model was then applied, based on the separate contributions of the leading and trailing edges of the sample plug, which computes the detector response. Peak heights, retention times and degree of overlap can then be optimized.

"Optimal Design Of An Enzymatic Reactor For Flow Injection Analysis"
Biotechnol. Prog. 1993 Volume 9, Issue 5 Pages 473-480
M. Poch, J. L. Montesinos, M. del Valle, J. Alonso, A. Araujo, and J. L. F. C. Lima

Abstract: A simulation procedure for the optimization of enzymatic reactors used in sandwich flow injection systems is evaluated. The system is modeled as a plug-flow reactor with axial dispersion. To calibrate it, dispersion coefficients can be evaluated using residence time distribution techniques; meanwhile, enzymatic kinetics must be determined for the system considered, according to the values of the substrate conversion attained. The model has been linked to an optimization routine based on the Powell algorithm. The proposed approach has been evaluated in a system performing simultaneous determinations of glucose and glycerol, considered the common carbon sources in a fermentation process.
Glucose Glycerol Fermentation broth

"Application Of The Powell Method To The Optimization Of Flow Injection Systems"
J. Chemom. 1988 Volume 3, Issue S1 Pages 285-292
M. del Valle, J. Alonso, M. Poch, J. Bartrol&iacute;

Abstract: This paper describes the application of the Powell algorithm to the optimization of a flow injection system configuration. The performance of this algorithm has been compared with the modified simplex method. The system studied is the determination of ammonia, based on the indophenol blue reaction. A linear combination of sensitivity and sample throughput is used as the objective function because of its simultaneous optimization capability. Results obtained show that the proposed method may reach the optimal conditions with a lower number of experimental evaluations.
Ammonia