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de Almeida VE, de Sousa Fernandes DD, Diniz PHGD, de Araújo Gomes A, Véras G, Galvão RKH, Araujo MCU. Scores selection via Fisher's discriminant power in PCA-LDA to improve the classification of food data. Food Chem 2021; 363:130296. [PMID: 34144419 DOI: 10.1016/j.foodchem.2021.130296] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Revised: 05/31/2021] [Accepted: 06/01/2021] [Indexed: 11/29/2022]
Abstract
This paper proposes an adaptation of the Fisher's discriminability criterion (named here as discriminant power, DP) for choosing principal components (obtained from Principal Component Analysis, PCA), which will be used to construct supervised Linear Discriminant Analysis (LDA) models for solving classification problems of food data. The proposed PCA-DP-LDA algorithm was then applied to (i) simulated data, (ii) classify soybean oils with respect to expiration date, and (iii) identify cachaça adulteration with wood extracts that simulated aging. For comparison, PCA-DP-LDA was evaluated against conventional PCA-LDA (based on explained variance) and Partial Least Squares-Discriminant Analysis (PLS-DA). Among them, PCA-DP-LDA achieved the most parsimonious and interpretable results, with similar or better classification performance. Therefore, the new algorithm can be considered a good alternative to the already well-established discriminant methods, being potentially applied where the discriminability of the principal components may not follow the same behavior of the explained variance.
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Affiliation(s)
- Valber Elias de Almeida
- Universidade Federal de Paraíba, Departamento de Química, P.O.Box 5093, CEP 58051-970 João Pessoa, PB, Brazil
| | | | | | - Adriano de Araújo Gomes
- Universidade Federal do Rio Grande do Sul, Departamento de Química Inorgânica, CEP 91501-970 Porto Alegre, RS, Brazil.
| | - Germano Véras
- Universidade Estadual da Paraíba, Centro de Ciência e Tecnologia, Departamento de Química, CEP 58429-500 Campina Grande, PB, Brazil
| | | | - Mario Cesar Ugulino Araujo
- Universidade Federal de Paraíba, Departamento de Química, P.O.Box 5093, CEP 58051-970 João Pessoa, PB, Brazil.
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Galvão RKH, Teixeira MCM, Assunção E, Paiva HM, Hadjiloucas S. Identification of fractional-order transfer functions using exponentially modulated signals with arbitrary excitation waveforms. ISA Trans 2020; 103:10-18. [PMID: 32278480 DOI: 10.1016/j.isatra.2020.03.027] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Revised: 03/10/2020] [Accepted: 03/20/2020] [Indexed: 06/11/2023]
Abstract
This paper proposes a new identification method based on an exponential modulation scheme for the determination of the coefficients and exponents of a fractional-order transfer function. The proposed approach has a broader scope of application compared to a previous method based on step response data, in that it allows for the use of arbitrary input signals. Moreover, it dispenses with the need for repeated simulations during the search for the best fractional exponents, which significantly reduces the computational workload involved in the identification process. Two examples involving measurement noise at the observed system output are presented to illustrate the effectiveness of the proposed method when compared to a conventional output-error optimization approach based on the polytope algorithm. In both examples, the proposed method is found to provide a better trade-off between computational workload and accuracy of the parameter estimates for different realizations of the noise.
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Affiliation(s)
| | | | - Edvaldo Assunção
- Department of Electrical Engineering, São Paulo State University (UNESP), Ilha Solteira, SP, Brazil
| | - Henrique Mohallem Paiva
- Institute of Science and Technology, Universidade Federal de São Paulo (UNIFESP), São José dos Campos, SP, Brazil
| | - Sillas Hadjiloucas
- School of Biological Sciences, Department of Biomedical Engineering, The University of Reading, Reading RG6 6AY, United Kingdom.
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de Almeida VE, de Araújo Gomes A, de Sousa Fernandes DD, Goicoechea HC, Galvão RKH, Araújo MCU. Vis-NIR spectrometric determination of Brix and sucrose in sugar production samples using kernel partial least squares with interval selection based on the successive projections algorithm. Talanta 2018; 181:38-43. [PMID: 29426528 DOI: 10.1016/j.talanta.2017.12.064] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2017] [Revised: 12/20/2017] [Accepted: 12/21/2017] [Indexed: 11/28/2022]
Affiliation(s)
- Valber Elias de Almeida
- Laboratório de Automação e Instrumentação em Química Analítica e Quimiometria (LAQA) Universidade Federal da Paraíba, CCEN, Departamento de Química, Caixa Postal 5093, CEP 58051-970, João Pessoa, PB, Brazil
| | - Adriano de Araújo Gomes
- Faculdade de Química, Instituto de Ciências Exatas da Universidade Federal do Sul e Sudoeste do Pará, Folha 17, Quadra 04, Lote Especial, Nova Marabá, CEP: 68.505.080, Marabá, Pará, Brazil
| | - David Douglas de Sousa Fernandes
- Laboratório de Automação e Instrumentação em Química Analítica e Quimiometria (LAQA) Universidade Federal da Paraíba, CCEN, Departamento de Química, Caixa Postal 5093, CEP 58051-970, João Pessoa, PB, Brazil
| | - Héctor Casimiro Goicoechea
- Laboratorio de Desarrollo Analítico y Quimiometría (LADAQ), Cátedra de Química Analítica I, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral-CONICET, Ciudad Universitaria, 3000 Santa Fe, Argentina
| | | | - Mario Cesar Ugulino Araújo
- Laboratório de Automação e Instrumentação em Química Analítica e Quimiometria (LAQA) Universidade Federal da Paraíba, CCEN, Departamento de Química, Caixa Postal 5093, CEP 58051-970, João Pessoa, PB, Brazil.
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Galvão RKH, Soares SFC, Martins MN, Pimentel MF, Araújo MCU. Calibration transfer employing univariate correction and robust regression. Anal Chim Acta 2015; 864:1-8. [DOI: 10.1016/j.aca.2014.10.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2014] [Revised: 09/23/2014] [Accepted: 10/02/2014] [Indexed: 10/24/2022]
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Goodarzi M, Saeys W, de Araujo MCU, Galvão RKH, Vander Heyden Y. Binary classification of chalcone derivatives with LDA or KNN based on their antileishmanial activity and molecular descriptors selected using the Successive Projections Algorithm feature-selection technique. Eur J Pharm Sci 2014; 51:189-95. [PMID: 24090733 DOI: 10.1016/j.ejps.2013.09.019] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2013] [Revised: 09/14/2013] [Accepted: 09/20/2013] [Indexed: 11/19/2022]
Abstract
Chalcones are naturally occurring aromatic ketones, which consist of an α-, β-unsaturated carbonyl system joining two aryl rings. These compounds are reported to exhibit several pharmacological activities, including antiparasitic, antibacterial, antifungal, anticancer, immunomodulatory, nitric oxide inhibition and anti-inflammatory effects. In the present work, a Quantitative Structure-Activity Relationship (QSAR) study is carried out to classify chalcone derivatives with respect to their antileishmanial activity (active/inactive) on the basis of molecular descriptors. For this purpose, two techniques to select descriptors are employed, the Successive Projections Algorithm (SPA) and the Genetic Algorithm (GA). The selected descriptors are initially employed to build Linear Discriminant Analysis (LDA) models. An additional investigation is then carried out to determine whether the results can be improved by using a non-parametric classification technique (One Nearest Neighbour, 1NN). In a case study involving 100 chalcone derivatives, the 1NN models were found to provide better rates of correct classification than LDA, both in the training and test sets. The best result was achieved by a SPA-1NN model with six molecular descriptors, which provided correct classification rates of 97% and 84% for the training and test sets, respectively.
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Affiliation(s)
- Mohammad Goodarzi
- Department of Biosystems, Faculty of Bioscience Engineering, Katholieke Universiteit Leuven - KULeuven, Kasteelpark Arenberg 30, B-3001 Heverlee, Belgium.
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Freitas SKB, Nascimento ECLD, Dionízio AGG, Gomes ADA, Araújo MCUD, Galvão RKH. A flow-batch analyzer using a low cost aquarium pump for classification of citrus juice with respect to brand. Talanta 2013; 107:45-8. [DOI: 10.1016/j.talanta.2012.12.027] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2012] [Revised: 11/29/2012] [Accepted: 12/21/2012] [Indexed: 10/27/2022]
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Pontes MJC, Gomes AA, Galvão RKH, Araújo MCU. Internal and External Validation in SPA-LDA: A Comparative Study Involving Diesel/Biodiesel Blends. ACTA ACUST UNITED AC 2012. [DOI: 10.1255/nirn.1313] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022]
Affiliation(s)
- Márcio José Coelho Pontes
- Universidade Federal da Paraíba, Departamento de Química—Laboratório de Automação e Instrumentaçáo em Química Analítica/Quimiometria (LAQA), Caixa Postal 5093, CEP 58051-970—João Pessoa, PB, Brazil
| | - Adriano Araújo Gomes
- Universidade Federal da Paraíba, Departamento de Química—Laboratório de Automação e Instrumentaçáo em Química Analítica/Quimiometria (LAQA), Caixa Postal 5093, CEP 58051-970—João Pessoa, PB, Brazil
| | | | - Mário César Ugulino Araújo
- Universidade Federal da Paraíba, Departamento de Química—Laboratório de Automação e Instrumentaçáo em Química Analítica/Quimiometria (LAQA), Caixa Postal 5093, CEP 58051-970—João Pessoa, PB, Brazil
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Marques de Melo R, Bottino MA, Galvão RKH, Soboyejo WO. Bond strengths, degree of conversion of the cement and molecular structure of the adhesive-dentine joint in fibre post restorations. J Dent 2012; 40:286-94. [PMID: 22306531 DOI: 10.1016/j.jdent.2012.01.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2011] [Revised: 12/28/2011] [Accepted: 01/02/2012] [Indexed: 10/14/2022] Open
Abstract
OBJECTIVES Because fibre post restorations are influenced by multiple factors such as the types of bonding materials, the dentine region and the time under moist exposure, this study sought to determine the bond strength of endodontic restorations and its relation to the degree of conversion of the cement layer and the molecular structure of the dentine-bonded joints. METHODS The performance of 2 etch-and-rinse (All-Bond 2 and One-Step Plus) and 2 self-etch (Clearfil SE Bond and Xeno III) adhesives at post spaces regions, after 7 d or 4 m, was evaluated. FRC Postec Plus posts were cemented to the root canal with a dual-cure resin cement (Duo-Link). Transverse sections of the tooth were subjected to push-out testing, to degree-of-conversion measurements and to hybrid layer evaluation through μ-Raman spectroscopy. RESULTS Coronal bonding was higher than cervical and middle bonding. The hybrid layer was thicker for the etch-and-rinse systems, with thicknesses decreasing towards the middle region. The degree of conversion measured for the 3-step etch-and-rinse group after 4 m was significantly higher than that for the self-etching groups. CONCLUSIONS Although not totally stable at the adhesive-dentine interface, the 3-step etch-and-rinse adhesive in the coronal dentine provided the best bond strength, degree of conversion of the cement and hybrid layer thickness in post restorations, in both short- and long-term analyses.
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Affiliation(s)
- Renata Marques de Melo
- Department of Dental Materials and Prosthodontics, São Paulo State University, São José dos Campos, São Paulo, Brazil.
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Souto UTCP, Pontes MJC, Silva EC, Galvão RKH, Araújo MCU, Sanches FAC, Cunha FAS, Oliveira MSR. UV–Vis spectrometric classification of coffees by SPA–LDA. Food Chem 2010. [DOI: 10.1016/j.foodchem.2009.05.078] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Moreira EDT, Pontes MJC, Galvão RKH, Araújo MCU. Near infrared reflectance spectrometry classification of cigarettes using the successive projections algorithm for variable selection. Talanta 2009; 79:1260-4. [PMID: 19635356 DOI: 10.1016/j.talanta.2009.05.031] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2009] [Revised: 05/15/2009] [Accepted: 05/18/2009] [Indexed: 11/17/2022]
Abstract
This paper proposes a methodology for cigarette classification employing Near Infrared Reflectance spectrometry and variable selection. For this purpose, the Successive Projections Algorithm (SPA) is employed to choose an appropriate subset of wavenumbers for a Linear Discriminant Analysis (LDA) model. The proposed methodology is applied to a set of 210 cigarettes of four different brands. For comparison, Soft Independent Modelling of Class Analogy (SIMCA) is also employed for full-spectrum classification. The resulting SPA-LDA model successfully classified all test samples with respect to their brands using only two wavenumbers (5058 and 4903 cm(-1)). In contrast, the SIMCA models were not able to achieve 100% of classification accuracy, regardless of the significance level adopted for the F-test. The results obtained in this investigation suggest that the proposed methodology is a promising alternative for assessment of cigarette authenticity.
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Goudarzi N, Goodarzi M, Araujo MCU, Galvão RKH. QSPR modeling of soil sorption coefficients (K(OC)) of pesticides using SPA-ANN and SPA-MLR. J Agric Food Chem 2009; 57:7153-7158. [PMID: 19722589 DOI: 10.1021/jf9008839] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
A quantitative structure-property relationship (QSPR) study was conducted to predict the adsorption coefficients of some pesticides. The successive projection algorithm feature selection (SPA) strategy was used as descriptor selection and model development method. Modeling of the relationship between selected molecular descriptors and adsorption coefficient data was achieved by linear (multiple linear regression; MLR) and nonlinear (artificial neural network; ANN) methods. The QSPR models were validated by cross-validation as well as application of the models to predict the K(OC) of external set compounds, which did not contribute to model development steps. Both linear and nonlinear methods provided accurate predictions, although more accurate results were obtained by the ANN model. The root-mean-square errors of test set obtained by MLR and ANN models were 0.3705 and 0.2888, respectively.
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Affiliation(s)
- Nasser Goudarzi
- Faculty of Chemistry, Shahrood University of Technology, P.O. Box 316, Shahrood, Iran.
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Pontes MJC, Cortez J, Galvão RKH, Pasquini C, Araújo MCU, Coelho RM, Chiba MK, de Abreu MF, Madari BE. Classification of Brazilian soils by using LIBS and variable selection in the wavelet domain. Anal Chim Acta 2009; 642:12-8. [DOI: 10.1016/j.aca.2009.03.001] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2008] [Accepted: 03/04/2009] [Indexed: 10/21/2022]
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Pereira CF, Pimentel MF, Galvão RKH, Honorato FA, Stragevitch L, Martins MN. A comparative study of calibration transfer methods for determination of gasoline quality parameters in three different near infrared spectrometers. Anal Chim Acta 2008; 611:41-7. [PMID: 18298965 DOI: 10.1016/j.aca.2008.01.071] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2007] [Revised: 01/24/2008] [Accepted: 01/25/2008] [Indexed: 11/16/2022]
Abstract
This work presents a comparative study of calibration transfer among three near infrared spectrometers for determination of naphthenes and RON (Research Octane Number) in gasoline. Seven transfer methods are compared: direct standardization (DS), piecewise direct standardization (PDS), orthogonal signal correction (OSC), reverse standardization (RS), piecewise reverse standardization (PRS), slope and bias correction (SBC) and model updating (MU). Two pre-treatment procedures, namely standard normal variate (SNV) and multiplicative scatter correction (MSC), are also investigated. The choice of an appropriate number of transfer samples for each technique, as well as the effect of window size in PDS/PRS and OSC components, are discussed. A broad set of gasoline samples representative of the Northeastern states of Brazil is employed in the investigation. The results show that the use of calibration transfer yields prediction errors comparable to those obtained with complete recalibration of the secondary instrument. Overall, the results point to RS as the best method for the analytical problem under consideration. When storage and/or physical transportation of transfer samples are impractical, MU is more appropriate. The comprehensive investigation carried out in the present work will be of value for practitioners involved in networks of fuel monitoring.
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Pimentel MF, Galvão RKH, Araújo MCUD. Recomendações para calibração em Química Analítica parte 2: calibração multianalito. QUIM NOVA 2008. [DOI: 10.1590/s0100-40422008000200047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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Pereira AFC, Pontes MJC, Neto FFG, Santos SRB, Galvão RKH, Araújo MCU. NIR spectrometric determination of quality parameters in vegetable oils using iPLS and variable selection. Food Res Int 2008. [DOI: 10.1016/j.foodres.2007.12.013] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Santos RNFD, Galvão RKH, Araujo MCU, Silva ECD. Improvement of prediction ability of PLS models employing the wavelet packet transform: A case study concerning FT-IR determination of gasoline parameters. Talanta 2007; 71:1136-43. [DOI: 10.1016/j.talanta.2006.06.023] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2006] [Revised: 06/02/2006] [Accepted: 06/03/2006] [Indexed: 11/25/2022]
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Galvão RKH, Araújo MCU, Silva EC, José GE, Soares SFC, Paiva HM. Cross-validation for the selection of spectral variables using the successive projections algorithm. J BRAZIL CHEM SOC 2007. [DOI: 10.1590/s0103-50532007000800021] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/03/2023] Open
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Galvão RKH, Filho HAD, Martins MN, Araújo MCU, Pasquini C. Sub-optimal wavelet denoising of coaveraged spectra employing statistics from individual scans. Anal Chim Acta 2007; 581:159-67. [PMID: 17386440 DOI: 10.1016/j.aca.2006.07.078] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2006] [Revised: 07/25/2006] [Accepted: 07/28/2006] [Indexed: 11/24/2022]
Abstract
This paper proposes a novel wavelet denoising method, which exploits the statistics of individual scans acquired in the course of a coaveraging process. The proposed method consists of shrinking the wavelet coefficients of the noisy signal by a factor that minimizes the expected square error with respect to the true signal. Since the true signal is not known, a sub-optimal estimate of the shrinking factor is calculated by using the sample statistics of the acquired scans. It is shown that such an estimate can be generated as the limit value of a recursive formulation. In a simulated example, the performance of the proposed method is seen to be equivalent to the best choice between hard and soft thresholding for different signal-to-noise ratios. Such a conclusion is also supported by an experimental investigation involving near-infrared (NIR) scans of a diesel sample. It is worth emphasizing that this experimental example concerns the removal of actual instrumental noise, in contrast to other case studies in the denoising literature, which usually present simulations with artificial noise. The simulated and experimental cases indicate that, in classic denoising based on wavelet coefficient thresholding, choosing between the hard and soft options is not straightforward and may lead to considerably different outcomes. By resorting to the proposed method, the analyst is not required to make such a critical decision in order to achieve appropriate results.
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Affiliation(s)
- Roberto Kawakami Harrop Galvão
- Universidade Federal da Paraíba, CCEN, Departamento de Química-Laboratório de Automação e Instrumentação em Química Analítica/Quimiometria (LAQA), Caixa Postal 5093, CEP 58051-970 João Pessoa, PB, Brazil
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Caneca AR, Pimentel MF, Galvão RKH, da Matta CE, de Carvalho FR, Raimundo Jr. IM, Pasquini C, Rohwedder JJ. Assessment of infrared spectroscopy and multivariate techniques for monitoring the service condition of diesel-engine lubricating oils. Talanta 2006; 70:344-52. [DOI: 10.1016/j.talanta.2006.02.054] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2005] [Revised: 02/18/2006] [Accepted: 02/18/2006] [Indexed: 10/24/2022]
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de Medeiros VM, Ugulino Araújo MC, Harrop Galvão RK, da Silva EC, Bezerra Saldanha TC, Salata Toscano IA, Ribeiro de Oliveira MDS, Barbosa Freitas SK, Neto MM. Screening analysis of river seston downstream of an effluent discharge point using near-infrared reflectance spectrometry and wavelet-based spectral region selection. Water Res 2005; 39:3089-97. [PMID: 15998532 DOI: 10.1016/j.watres.2005.05.018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2004] [Revised: 05/16/2005] [Accepted: 05/18/2005] [Indexed: 05/03/2023]
Abstract
A methodology for screening analysis of river seston downstream of an industry effluent by using near-infrared reflectance spectrometry was developed. A wavelet transform (WT)-based strategy is used to select a spectral region in which the effect of the effluent on the optical properties of the seston is more evident. The methodology was applied to samples from the River Mumbaba in northeast Brazil. Four sites were monitored: two upstream (1 and 2), one at the discharge point of the effluent (3), and another downstream (4). Soft Independent Modelling of Class Analogies (SIMCA) models were built for site 1 and were then applied to the classification of samples from sites 2 and 4. The results reveal that the WT-based spectral region selection is essential to ensure good sensitivity and specificity with respect to the detection of events associated to the effluent discharges at site 3. In fact, the changes in site 4 caused by the effluent are masked by other environmental factors when the full spectrum is employed.
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Affiliation(s)
- Vânia Maria de Medeiros
- Universidade Federal da Paraíba, CCEN, Departamento de Química, Caixa Postal 5093, 58051-970-João Pessoa, PB, Brazil
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Martins VL, de Almeida LF, de Castro SL, Galvão RKH, de Araújo MCU, da Silva EC. A Multiscale Wavelet Data Treatment for Reliable Localization of Inflection Points for Analytical Purposes. ACTA ACUST UNITED AC 2003; 43:1725-32. [PMID: 14632417 DOI: 10.1021/ci034112w] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Instrumental analysis techniques that employ measurements based on inflection points may have their accuracy compromised due to the need for signal differentiation, which is very sensitive to instrumental noise. This paper presents a strategy for localizing inflection points that exploits the multiscale processing capability of the Wavelet Transform and avoids the need for explicit signal differentiation. The strategy is illustrated in simulated examples and also in a real analytical problem involving the determination of Pb and Cd by potentiometric stripping analysis. In this application, the results were in good agreement with the expected values and were slightly better than those obtained from the first derivative of the curves after smoothing by a Windowed Fourier Transform.
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Affiliation(s)
- Valdomiro Lacerda Martins
- Departamento de Química Fundamental, Universidade Federal de Pernambuco, CCEN, CEP 50740-901 - Recife PE, Brazil
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Galvão RKH, Hadjiloucas S, Bowen JW. Use of the statistical properties of the wavelet-transform coefficients for optimization of integration time in Fourier transform spectrometry. Opt Lett 2002; 27:643-645. [PMID: 18007889 DOI: 10.1364/ol.27.000643] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
We show that an analysis of the mean and variance of discrete wavelet coefficients of coaveraged time-domain interferograms can be used as a specification for determining when to stop coaveraging. We also show that, if a prediction model built in the wavelet domain is used to determine the composition of unknown samples, a stopping criterion for the coaveraging process can be developed with respect to the uncertainty tolerated in the prediction.
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Galvão RKH, Araújo MCUD, Saldanha TCB, Visani V, Pimentel MF. Estudo comparativo sobre filtragem de sinais instrumentais usando transformadas de Fourier e Wavelet. QUIM NOVA 2001. [DOI: 10.1590/s0100-40422001000600026] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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