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Research paper thumbnail of Inversion of turbidity measurements of polymer latex using wavelet functions

Chemometrics and Intelligent Laboratory Systems, Apr 1, 1999

Research paper thumbnail of Inversion of turbidity measurements of polymer latex using wavelet functions

Chemometrics and Intelligent Laboratory Systems, 1999

Research paper thumbnail of Deconvolution by spline funtions to estimate the relaxation spectrum of viscoelastic fluids

Latin American Applied Research, 1995

Research paper thumbnail of Model Reference Adaptive Control of a Certain Class of Non-Linear System

1985 American Control Conference, 1985

An adaptive model following control (AMFC) technique is developed which considers: a) non-linear ... more An adaptive model following control (AMFC) technique is developed which considers: a) non-linear plant models of the class: X<inf>p</inf>=g(x<inf>p</inf>)+P(x<inf>p</inf>)u<inf>p</inf> with dim(x<inf>p</inf>)=dim(u<inf>p</inf>) and P(x<inf>p</inf>) invertible ¿x<inf>p</inf>; and b) non-linear reference models of the class X<inf>m</inf>=m(x<inf>m</inf>, r). The proposed technique is applied to a simulated example, which consists of a periodically operated chemical reactor.

Research paper thumbnail of Assessment of the modeling error of an approximate Light Scattering model by processing accurate simulated data

2016 IEEE Biennial Congress of Argentina (ARGENCON), 2016

This paper presents the analysis of the modeling error of an approximate model in a Static Light ... more This paper presents the analysis of the modeling error of an approximate model in a Static Light Scattering (SLS) problem for the morphological characterization of particle systems through the estimation of the Particle Size Distribution (PSD). The modelling error of the employed approximate model called the Local Monodisperse Approximation (LMA) is obtained by means of processing simulated data generated by a theoretically accurate model called the Vrij's Finite Mixture Model (VFMM). As a simplification on the procedure, PSDs are supposed to be well-represented by a log-normal distribution. The data generated by the VFMM is processed by solving an inverse parametric problem using a Least-Squares approach. Bias on estimations is studied in function of all significant system parameters.

Research paper thumbnail of Relaci�n entre el grado de discretizaci�n y la resoluci�n de un problema in- verso lineal

Research paper thumbnail of A method solving an inverse problem with unknown parameters from two sets of relative measurements

Latin American Applied Research, Apr 1, 2005

This work deals with an ill-posed inverse problem in which a distribution function, f(x), is esti... more This work deals with an ill-posed inverse problem in which a distribution function, f(x), is estimated from two independent sets of nonnegative relative measurements. Each measurement set is modeled through a Fredholm equation of the first kind, with unknown parameters in its kernel. While the first measurement model only includes a scalar unknown parameter, p 0 , the second model contains a vector of unknown parameters, p. The proposed method consists of the following steps: (i) to obtain a first estimate of f(x) and p 0 from the first measurement; (ii) to estimate the vector p from the second measurement and the previous estimate of f(x); and (iii) to estimate an improved f(x) by simultaneously using both measurements and the estimated parameters in a unique combined problem. The proposed algorithm is evaluated through a numerical example for simultaneously estimating the particle size distribution and the refractive index of a polymer latex, from combined measurements of elastic light scattering and turbidity. Keywords−− Inverse problem; parameter estimation; combined measurements; ELS; Turbidity.

Research paper thumbnail of Determination of the Particle Size Distribution of Latex Using a Combination of Elastic Light Scattering and Turbidimetry: A Simulation Study

Journal of Colloid and Interface Science, Aug 10, 1996

Turbidimetry at several wavelengths and elastic light scattering (ELS) at several angles can be u... more Turbidimetry at several wavelengths and elastic light scattering (ELS) at several angles can be used to determine particle size distributions (PSDs) of suspended particles using Mie scattering theory. The limited range of measurement in reciprocal space and the measurement noise always cause both techniques to have their own limitations. In this work, a way to combine turbidimetry and ELS data to be processed together is proposed. In order to investigate the convenience of simultaneous versus individual processing, a set of computationally generated experiments performed on suspensions of polystyrene particles is analyzed. The results clearly show that when the data are jointly processed the quality of the PSDs obtained is highly superior. This fact can be explained by the complementary characteristics of both techniques. Turbidimetry is more accurate at larger sizes, whereas ELS gives more precise estimations at smaller sizes. This work shows that simultaneous processing of experimental data from different sources seems to be a valid alternative for improving the quality of indirect measurements.

Research paper thumbnail of Relación entre el grado de discretización y la resolución de un problema in- verso lineal

Research paper thumbnail of Método iterativo combinado con proyección por splines y optimizado con lógica difusa para el procesamiento de mediciones de dispersión de luz estática en sistemas de partículas bajo el régimen de Rayleigh-Gans

Método iterativo combinado con proyección por splines y optimizado con lógica difusa para el proc... more Método iterativo combinado con proyección por splines y optimizado con lógica difusa para el procesamiento de mediciones de dispersión de luz estática en sistemas de partículas bajo el régimen de Rayleigh-Gans

Research paper thumbnail of A Method for Solving an Inverse Problem with Unknown Parameters from Two Sets of Relative Measurements

Latin American applied research Pesquisa aplicada latino americana = Investigación aplicada latinoamericana

This work deals with an ill-posed inverse problem in which a distribution function, f(x), is esti... more This work deals with an ill-posed inverse problem in which a distribution function, f(x), is estimated from two independent sets of non-negative relative measurements. Each measurement set is modeled through a Fredhohn equation of the first kind, with unknown parameters in its kernel. While the first measurement model only includes a scalar unknown parameter, p0, the second model contains a vector of unknown parameters, p. The proposed method consists of the following steps: (i) to obtain a first estimate of f(x) and p0 from the first measurement; (ii) to estimate the vector p from the second measurement and the previous estimate of f(x); and (iii) to estimate an improved f(x) by simultaneously using both measurements and the estimated parameters in a unique combined problem. The proposed algorithm is evaluated through a numerical example for simultaneously estimating the particle size distribution and the refractive index of a polymer latex, from combined measurements of elastic light scattering and turbidity.Fil: Vega, Jorge Ruben. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Frontini, Gloria Lia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Gugliotta, Luis Marcelino. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Elicabe, Guillermo Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin

Research paper thumbnail of Presentación MACI2015 revisada 12 6 5

Research paper thumbnail of Bayesian Analysis Applied to the Estimation of Particle Size Distribution from Light Scattering Measurements

This article presents a Bayesian approach to the solution of a scattering inverse problem. Our pa... more This article presents a Bayesian approach to the solution of a scattering inverse problem. Our particular interest is the estimation of the particle size distribution (PSD) of a colloidal system of spherical particles using measurements of Static Light Scattering (SLS). For concentrated particle systems, with low contrast between media and particles, i.e., polymeric particles suspended in a different polymeric medium, the approximate model due to Pedersen [1] can be appropriate. We assume that the distribution can be well described by a log-normal function, with only two unknowns related to the mean and variance. The developed implementation makes use of the Metropolis-Hastings algorithm. We explored the effects of the algorithm parameters on the obtained estimations. We have also analyzed the reduction on the number of parameters in the used models. The solutions confidence intervals were estimated.

Research paper thumbnail of Enfoque Bayesiano Para La Inversión No Paramétrica De Mediciones De Dispersión De Luz

Resumen. En este trabajo resolvemos el problema inverso de estimar la Distribución de Tamaño de P... more Resumen. En este trabajo resolvemos el problema inverso de estimar la Distribución de Tamaño de Partículas (DTP) a partir de mediciones de Dispersión de Luz Estática (DLE) empleando un modelo aproximado denominado Aproximación Local Monodispersa (ALM). La estimación de la DTP es resuelta mediante un esquema de forma libre donde no hay suposición de la forma de la distribución y empleando un enfoque Bayesiano. En trabajos anteriores, se ha empleado un enfoque determinístico con métodos basados en la maximización de la función de máxima verosimilitud. Sin embargo los errores de modelado introducidos por la ALM producen un empobrecimiento en los resultados obtenidos con estos métodos. Los métodos de enfoque Bayesiano ofrecen una interesante alternativa donde es posible incluir información adicional para obtener una mejora en las estimaciones así como un cálculo de los intervalos de confianza. El Método Iterativo Bayesiano (MIB) que se desarrolla aquí está basado en el algoritmo Metropo...

Research paper thumbnail of Solución De Un Problema Inverso Mediante Proyección Por Splines

Research paper thumbnail of Inversión de señales de Dispersión de Luz para estimar Distribución de Tamaños con enfoque Bayesiano

Resumen La inversión de Mediciones de Dis-persión de Luz Estática (DLE) para estimar la Dis-tribu... more Resumen La inversión de Mediciones de Dis-persión de Luz Estática (DLE) para estimar la Dis-tribución de Tamaños de Partículas (DTP) de una emulsión polimérica se realiza con enfoque bayesia-no incorporando información previa obtenida de mediciones de Microscopía Electrónica de Barrido (MEB). El problema directo emplea un modelo aproximado denominado Aproximación Local Mo-nodispersa (ALM). El objetivo propuesto es obtener resultados sobre datos experimentales más consisten-tes con los obtenidos por MEB en un trabajo previo. Para la resolución del problema inverso se hace uso del algoritmo de Metropolis-Hastings. Los resul-tados obtenidos muestran que el enfoque bayesiano resulta apropiado cuando el mismo se aplica sobre modelos aproximados y se cuenta con información previa confiable.

Research paper thumbnail of Estimación y Regularización en Problemas Inversos en Ingeniería

Resumen. Este trabajo presenta una breve revisión de los conceptos de estimación y regularización... more Resumen. Este trabajo presenta una breve revisión de los conceptos de estimación y regularización en el área de problemas inversos. Tras una básica descripción del marco teórico de los problemas inversos se introducen dos conceptos fundamentales en el área como son los de estimación y regularización. Finalmente se concluye con una breve recapitulación de dos ejemplos de problemas inversos específicos en los que los autores han estado trabajando, señalando algunos de los resultados obtenidos en relación con la temática abordada.

Research paper thumbnail of Particle Systems Characterization Using a Flat Cell Static Light Scattering Apparatus

Particle & Particle Systems Characterization, 2007

ABSTRACT In this work a light scattering apparatus for the study of heterogeneous liquid systems ... more ABSTRACT In this work a light scattering apparatus for the study of heterogeneous liquid systems of evolving morphology is presented. A Fraunhofer configuration consisting of a linear array of photodiodes is used to detect the light scattered by thin samples illuminated by a He-Ne laser light. Temperature control is available. The instrument is tested with the polymerization induced phase separation of a thermosetting polymer formulated with a divinylester resin copolymerized with styrene and modified with poly(methylmethacrylate). The system is successfully modeled as an arrangement of particles growing in size and number, and varying in composition. The ability of the experimental setup to provide results that can be quantitatively analyzed is checked using microspherical polystyrene standards. Different samples with nominal sizes of 0.5, 1 and 2 μm are used in different combinations of sample thickness and concentration. The analysis of the light scattering spectra is performed using inverse techniques to estimate the particle size distribution of the microspheres. The results agree with previous knowledge of the parameters of the samples.

Research paper thumbnail of Particle Size Distribution by Combined Elastic Light Scattering and Turbidity Measurements. A Novel Method to Estimate the Required Normalization Factor

Particle & Particle Systems Characterization, 2003

... A Novel Method to Estimate the Required Normalization Factor Jorge R. Vega*, Gloria L. Fronti... more ... A Novel Method to Estimate the Required Normalization Factor Jorge R. Vega*, Gloria L. Frontini**, Luis M. Gugliotta*, Guillermo E. EliÁabe** (Received: 12 December 2002; in revised form: 24 June 2003; accepted: 26 July 2003) Abstract ... Then: t kAt fr et (7.a) i AI fr eI . (7.b) ...

Research paper thumbnail of Evaluation of light scattering models to characterize concentrated polymer particles embedded in a solid polymer matrix

Journal of Polymer Science Part B: Polymer Physics, 2010

This work deals with the application of the static light scattering (SLS) model of Vrij (VM) for ... more This work deals with the application of the static light scattering (SLS) model of Vrij (VM) for the characterization of a spherical polydisperse concentrated polymer particle system. This model is the exact solution for the SLS of such mixture of particles in the Percus-Yevick approximation. The analyzed polymer particle samples are obtained by solution polymerization of isobornyl methacrylate in polyisobutylene. At the end of the polymerization, as a result of phase separation, a particle system of micrometer sized particles with a moderate distribution of sizes and a volume fraction between 5 and 10% is formed. The SLS data were also analyzed using the local monodisperse approximation (LMA), a well-known approximation to the model of Vrij. As expected, the estimations with the VM gave better results than those performed with the LMA model for the parameters related to the shape of the particle size distribution as compared with independent determinations of these quantities obtained from scanning electron microscopy micrographs. However, the main motivation to use the more rigorous model seems to be the fact that the volume fraction of particles can be extracted from the data even when relative SLS measurements are used. V

Research paper thumbnail of Inversion of turbidity measurements of polymer latex using wavelet functions

Chemometrics and Intelligent Laboratory Systems, Apr 1, 1999

Research paper thumbnail of Inversion of turbidity measurements of polymer latex using wavelet functions

Chemometrics and Intelligent Laboratory Systems, 1999

Research paper thumbnail of Deconvolution by spline funtions to estimate the relaxation spectrum of viscoelastic fluids

Latin American Applied Research, 1995

Research paper thumbnail of Model Reference Adaptive Control of a Certain Class of Non-Linear System

1985 American Control Conference, 1985

An adaptive model following control (AMFC) technique is developed which considers: a) non-linear ... more An adaptive model following control (AMFC) technique is developed which considers: a) non-linear plant models of the class: X<inf>p</inf>=g(x<inf>p</inf>)+P(x<inf>p</inf>)u<inf>p</inf> with dim(x<inf>p</inf>)=dim(u<inf>p</inf>) and P(x<inf>p</inf>) invertible ¿x<inf>p</inf>; and b) non-linear reference models of the class X<inf>m</inf>=m(x<inf>m</inf>, r). The proposed technique is applied to a simulated example, which consists of a periodically operated chemical reactor.

Research paper thumbnail of Assessment of the modeling error of an approximate Light Scattering model by processing accurate simulated data

2016 IEEE Biennial Congress of Argentina (ARGENCON), 2016

This paper presents the analysis of the modeling error of an approximate model in a Static Light ... more This paper presents the analysis of the modeling error of an approximate model in a Static Light Scattering (SLS) problem for the morphological characterization of particle systems through the estimation of the Particle Size Distribution (PSD). The modelling error of the employed approximate model called the Local Monodisperse Approximation (LMA) is obtained by means of processing simulated data generated by a theoretically accurate model called the Vrij's Finite Mixture Model (VFMM). As a simplification on the procedure, PSDs are supposed to be well-represented by a log-normal distribution. The data generated by the VFMM is processed by solving an inverse parametric problem using a Least-Squares approach. Bias on estimations is studied in function of all significant system parameters.

Research paper thumbnail of Relaci�n entre el grado de discretizaci�n y la resoluci�n de un problema in- verso lineal

Research paper thumbnail of A method solving an inverse problem with unknown parameters from two sets of relative measurements

Latin American Applied Research, Apr 1, 2005

This work deals with an ill-posed inverse problem in which a distribution function, f(x), is esti... more This work deals with an ill-posed inverse problem in which a distribution function, f(x), is estimated from two independent sets of nonnegative relative measurements. Each measurement set is modeled through a Fredholm equation of the first kind, with unknown parameters in its kernel. While the first measurement model only includes a scalar unknown parameter, p 0 , the second model contains a vector of unknown parameters, p. The proposed method consists of the following steps: (i) to obtain a first estimate of f(x) and p 0 from the first measurement; (ii) to estimate the vector p from the second measurement and the previous estimate of f(x); and (iii) to estimate an improved f(x) by simultaneously using both measurements and the estimated parameters in a unique combined problem. The proposed algorithm is evaluated through a numerical example for simultaneously estimating the particle size distribution and the refractive index of a polymer latex, from combined measurements of elastic light scattering and turbidity. Keywords−− Inverse problem; parameter estimation; combined measurements; ELS; Turbidity.

Research paper thumbnail of Determination of the Particle Size Distribution of Latex Using a Combination of Elastic Light Scattering and Turbidimetry: A Simulation Study

Journal of Colloid and Interface Science, Aug 10, 1996

Turbidimetry at several wavelengths and elastic light scattering (ELS) at several angles can be u... more Turbidimetry at several wavelengths and elastic light scattering (ELS) at several angles can be used to determine particle size distributions (PSDs) of suspended particles using Mie scattering theory. The limited range of measurement in reciprocal space and the measurement noise always cause both techniques to have their own limitations. In this work, a way to combine turbidimetry and ELS data to be processed together is proposed. In order to investigate the convenience of simultaneous versus individual processing, a set of computationally generated experiments performed on suspensions of polystyrene particles is analyzed. The results clearly show that when the data are jointly processed the quality of the PSDs obtained is highly superior. This fact can be explained by the complementary characteristics of both techniques. Turbidimetry is more accurate at larger sizes, whereas ELS gives more precise estimations at smaller sizes. This work shows that simultaneous processing of experimental data from different sources seems to be a valid alternative for improving the quality of indirect measurements.

Research paper thumbnail of Relación entre el grado de discretización y la resolución de un problema in- verso lineal

Research paper thumbnail of Método iterativo combinado con proyección por splines y optimizado con lógica difusa para el procesamiento de mediciones de dispersión de luz estática en sistemas de partículas bajo el régimen de Rayleigh-Gans

Método iterativo combinado con proyección por splines y optimizado con lógica difusa para el proc... more Método iterativo combinado con proyección por splines y optimizado con lógica difusa para el procesamiento de mediciones de dispersión de luz estática en sistemas de partículas bajo el régimen de Rayleigh-Gans

Research paper thumbnail of A Method for Solving an Inverse Problem with Unknown Parameters from Two Sets of Relative Measurements

Latin American applied research Pesquisa aplicada latino americana = Investigación aplicada latinoamericana

This work deals with an ill-posed inverse problem in which a distribution function, f(x), is esti... more This work deals with an ill-posed inverse problem in which a distribution function, f(x), is estimated from two independent sets of non-negative relative measurements. Each measurement set is modeled through a Fredhohn equation of the first kind, with unknown parameters in its kernel. While the first measurement model only includes a scalar unknown parameter, p0, the second model contains a vector of unknown parameters, p. The proposed method consists of the following steps: (i) to obtain a first estimate of f(x) and p0 from the first measurement; (ii) to estimate the vector p from the second measurement and the previous estimate of f(x); and (iii) to estimate an improved f(x) by simultaneously using both measurements and the estimated parameters in a unique combined problem. The proposed algorithm is evaluated through a numerical example for simultaneously estimating the particle size distribution and the refractive index of a polymer latex, from combined measurements of elastic light scattering and turbidity.Fil: Vega, Jorge Ruben. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Frontini, Gloria Lia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Gugliotta, Luis Marcelino. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Elicabe, Guillermo Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin

Research paper thumbnail of Presentación MACI2015 revisada 12 6 5

Research paper thumbnail of Bayesian Analysis Applied to the Estimation of Particle Size Distribution from Light Scattering Measurements

This article presents a Bayesian approach to the solution of a scattering inverse problem. Our pa... more This article presents a Bayesian approach to the solution of a scattering inverse problem. Our particular interest is the estimation of the particle size distribution (PSD) of a colloidal system of spherical particles using measurements of Static Light Scattering (SLS). For concentrated particle systems, with low contrast between media and particles, i.e., polymeric particles suspended in a different polymeric medium, the approximate model due to Pedersen [1] can be appropriate. We assume that the distribution can be well described by a log-normal function, with only two unknowns related to the mean and variance. The developed implementation makes use of the Metropolis-Hastings algorithm. We explored the effects of the algorithm parameters on the obtained estimations. We have also analyzed the reduction on the number of parameters in the used models. The solutions confidence intervals were estimated.

Research paper thumbnail of Enfoque Bayesiano Para La Inversión No Paramétrica De Mediciones De Dispersión De Luz

Resumen. En este trabajo resolvemos el problema inverso de estimar la Distribución de Tamaño de P... more Resumen. En este trabajo resolvemos el problema inverso de estimar la Distribución de Tamaño de Partículas (DTP) a partir de mediciones de Dispersión de Luz Estática (DLE) empleando un modelo aproximado denominado Aproximación Local Monodispersa (ALM). La estimación de la DTP es resuelta mediante un esquema de forma libre donde no hay suposición de la forma de la distribución y empleando un enfoque Bayesiano. En trabajos anteriores, se ha empleado un enfoque determinístico con métodos basados en la maximización de la función de máxima verosimilitud. Sin embargo los errores de modelado introducidos por la ALM producen un empobrecimiento en los resultados obtenidos con estos métodos. Los métodos de enfoque Bayesiano ofrecen una interesante alternativa donde es posible incluir información adicional para obtener una mejora en las estimaciones así como un cálculo de los intervalos de confianza. El Método Iterativo Bayesiano (MIB) que se desarrolla aquí está basado en el algoritmo Metropo...

Research paper thumbnail of Solución De Un Problema Inverso Mediante Proyección Por Splines

Research paper thumbnail of Inversión de señales de Dispersión de Luz para estimar Distribución de Tamaños con enfoque Bayesiano

Resumen La inversión de Mediciones de Dis-persión de Luz Estática (DLE) para estimar la Dis-tribu... more Resumen La inversión de Mediciones de Dis-persión de Luz Estática (DLE) para estimar la Dis-tribución de Tamaños de Partículas (DTP) de una emulsión polimérica se realiza con enfoque bayesia-no incorporando información previa obtenida de mediciones de Microscopía Electrónica de Barrido (MEB). El problema directo emplea un modelo aproximado denominado Aproximación Local Mo-nodispersa (ALM). El objetivo propuesto es obtener resultados sobre datos experimentales más consisten-tes con los obtenidos por MEB en un trabajo previo. Para la resolución del problema inverso se hace uso del algoritmo de Metropolis-Hastings. Los resul-tados obtenidos muestran que el enfoque bayesiano resulta apropiado cuando el mismo se aplica sobre modelos aproximados y se cuenta con información previa confiable.

Research paper thumbnail of Estimación y Regularización en Problemas Inversos en Ingeniería

Resumen. Este trabajo presenta una breve revisión de los conceptos de estimación y regularización... more Resumen. Este trabajo presenta una breve revisión de los conceptos de estimación y regularización en el área de problemas inversos. Tras una básica descripción del marco teórico de los problemas inversos se introducen dos conceptos fundamentales en el área como son los de estimación y regularización. Finalmente se concluye con una breve recapitulación de dos ejemplos de problemas inversos específicos en los que los autores han estado trabajando, señalando algunos de los resultados obtenidos en relación con la temática abordada.

Research paper thumbnail of Particle Systems Characterization Using a Flat Cell Static Light Scattering Apparatus

Particle & Particle Systems Characterization, 2007

ABSTRACT In this work a light scattering apparatus for the study of heterogeneous liquid systems ... more ABSTRACT In this work a light scattering apparatus for the study of heterogeneous liquid systems of evolving morphology is presented. A Fraunhofer configuration consisting of a linear array of photodiodes is used to detect the light scattered by thin samples illuminated by a He-Ne laser light. Temperature control is available. The instrument is tested with the polymerization induced phase separation of a thermosetting polymer formulated with a divinylester resin copolymerized with styrene and modified with poly(methylmethacrylate). The system is successfully modeled as an arrangement of particles growing in size and number, and varying in composition. The ability of the experimental setup to provide results that can be quantitatively analyzed is checked using microspherical polystyrene standards. Different samples with nominal sizes of 0.5, 1 and 2 μm are used in different combinations of sample thickness and concentration. The analysis of the light scattering spectra is performed using inverse techniques to estimate the particle size distribution of the microspheres. The results agree with previous knowledge of the parameters of the samples.

Research paper thumbnail of Particle Size Distribution by Combined Elastic Light Scattering and Turbidity Measurements. A Novel Method to Estimate the Required Normalization Factor

Particle & Particle Systems Characterization, 2003

... A Novel Method to Estimate the Required Normalization Factor Jorge R. Vega*, Gloria L. Fronti... more ... A Novel Method to Estimate the Required Normalization Factor Jorge R. Vega*, Gloria L. Frontini**, Luis M. Gugliotta*, Guillermo E. EliÁabe** (Received: 12 December 2002; in revised form: 24 June 2003; accepted: 26 July 2003) Abstract ... Then: t kAt fr et (7.a) i AI fr eI . (7.b) ...

Research paper thumbnail of Evaluation of light scattering models to characterize concentrated polymer particles embedded in a solid polymer matrix

Journal of Polymer Science Part B: Polymer Physics, 2010

This work deals with the application of the static light scattering (SLS) model of Vrij (VM) for ... more This work deals with the application of the static light scattering (SLS) model of Vrij (VM) for the characterization of a spherical polydisperse concentrated polymer particle system. This model is the exact solution for the SLS of such mixture of particles in the Percus-Yevick approximation. The analyzed polymer particle samples are obtained by solution polymerization of isobornyl methacrylate in polyisobutylene. At the end of the polymerization, as a result of phase separation, a particle system of micrometer sized particles with a moderate distribution of sizes and a volume fraction between 5 and 10% is formed. The SLS data were also analyzed using the local monodisperse approximation (LMA), a well-known approximation to the model of Vrij. As expected, the estimations with the VM gave better results than those performed with the LMA model for the parameters related to the shape of the particle size distribution as compared with independent determinations of these quantities obtained from scanning electron microscopy micrographs. However, the main motivation to use the more rigorous model seems to be the fact that the volume fraction of particles can be extracted from the data even when relative SLS measurements are used. V