Vibration-Based structural health monitoring using piezoelectric transducers and parametric t-SNE

In this paper, we evaluate the performance of the so-called parametric t-distributed stochastic neighbor embedding (P-t-SNE), comparing it to the performance of the t-SNE, the non-parametric version. The methodology used in this study is introduced for the detection and classification of structural changes in the field of structural health monitoring. This method is based on the combination of principal component analysis (PCA) and P-t-SNE, and it is applied to an experimental case study of an aluminum plate with four piezoelectric transducers. The basic steps of the detection and classification process are: (i) the raw data are scaled using mean-centered group scaling and then PCA is applied to reduce its dimensionality; (ii) P-t-SNE is applied to represent the scaled and reduced data as 2-dimensional points, defining a cluster for each structural state; and (iii) the current structure to be diagnosed is associated with a cluster employing two strategies: (a) majority voting; and (b) the sum of the inverse distances. The results in the frequency domain manifest the strong performance of P-t-SNE, which is comparable to the performance of t-SNE but outperforms t-SNE in terms of computational cost and runtime. When the method is based on P-t-SNE, the overall accuracy fluctuates between 99.5% and 99.75%.Peer ReviewedPostprint (published version

Damage diagnosis for offshore fixed wind turbines

This paper proposes a damage diagnosis strategy to detect and classify different type of damages in a laboratory offshore-fixed wind turbine model. The proposed method combines an accelerometer sensor network attached to the structure with a conceived algorithm based on principal component analysis (PCA) with quadratic discriminant analysis (QDA). The paradigm of structural health monitoring can be undertaken as a pattern recognition problem (comparison between the data collected from the healthy structure and the current structure to diagnose given a known excitation). However, in this work, as the strategy is designed for wind turbines, only the output data from the sensors is used but the excitation is assumed unknown (as in reality is provided by the wind). The proposed methodology is tested in an experimental laboratory tower modeling an offshore-fixed jacked-type wind turbine. The obtained results show the reliability of the proposed approach.Peer ReviewedPostprint (published version

A frequency-based approach for the detection and classification of structural changes using t-SNE

This work presents a structural health monitoring (SHM) approach for the detection and classification of structural changes. The proposed strategy is based on t-distributed stochastic neighbor embedding (t-SNE), a nonlinear procedure that is able to represent the local structure of high-dimensional data in a low-dimensional space. The steps of the detection and classification procedure are: (i) the data collected are scaled using mean-centered group scaling (MCGS); (ii) then principal component analysis (PCA) is applied to reduce the dimensionality of the data set; (iii) t-SNE is applied to represent the scaled and reduced data as points in a plane defining as many clusters as different structural states; and (iv) the current structure to be diagnosed will be associated with a cluster or structural state based on three strategies: (a) the smallest point-centroid distance; (b) majority voting; and (c) the sum of the inverse distances. The combination of PCA and t-SNE improves the quality of the clusters related to the structural states. The method is evaluated using experimental data from an aluminum plate with four piezoelectric transducers (PZTs). Results are illustrated in frequency domain, and they manifest the high classification accuracy and the strong performance of this method.Peer ReviewedPostprint (published version

Modelos GEE para el análisis de la evolución de las lesiones acnéicas tratadas con Nadixa

El profesor Bakar Bouadjar del departamento de dermatología (CHU de Bab-el-Oued,Argelia) y Laboratorios Ferrer quieren estudiar la evolución de los pacientes tratados con Nadixa crema 1% para el acné a través de un estudio longitudinal no comparativo. Para el estudio se seleccionaron 30 pacientes con lesiones inflamatorias de acné vulgar con una gravedad leve-moderada. En la semana basal se realizó un recuento de lesiones y en las semanas 2, 4, 8 y 12 se evaluaron la eficacia y la tolerabilidad cutánea. De los pacientes, 22 son mujeres y 7 son hombres. La edad media (± SD) de los pacientes es de 21,7 años (± 4,45) y la duración media (± SD) de la enfermedad es de 48,19 meses (± 25,04). Se ha observado un descenso en el número de lesiones inflamatorias (pápulas, pústulas y nódulos) del -80,6%(IC95% [-81,6% ; -79,9%]). En cambio, el número de lesiones no inflamatorias (quistes, lesiones residuales y cicatrices), se mantiene prácticamente constante en el tiempo. Respecto a la tolerabilidad al medicamento, la probabilidad de tener eritema y prurito disminuye en los individuos a medida que transcurre el tiempo: se pasa de tener una probabilidad del 65,1% (IC95% [50,5% ; 77,3%]) y del 48,7% (IC95% [33,6% ; 64,1%]), respectivamente, en la semana 2, a tener 0,9% (IC95% [0,1% ; 6,7%]) y 0,3% (IC95% [0,02% ; 5,3%]) al final del tratamiento. Sin embargo, la probabilidad de que se produzca descamación y sequedad no decrece de forma clara a medida que avanzan las semanas: se pasa de tener una probabilidad del 44,7% (IC95% [30,8% ; 59,5%]) y del 52% (IC95% [37,6% ; 66,2%]), respectivamente, en la semana 2, a tener 21,8% (IC95% [10,6% ; 39,8%]) y 26,4% (IC95% [13,6% ; 44,9%]) en la semana 12. En conclusión, después de doce semanas de tratamiento con Nadixa, se ha observado una disminución general en las lesiones inflamatorias causadas por el acné. También se ha observado que, en general, la probabilidad de padecer las reacciones adversas eritema y/o prurito disminuye de forma muy rápida, ya que se produce desde las primeras semanas

Damage identification in structural health monitoring: a brief review from its implementation to the Use of data-driven applications

The damage identification process provides relevant information about the current state of a structure under inspection, and it can be approached from two different points of view. The first approach uses data-driven algorithms, which are usually associated with the collection of data using sensors. Data are subsequently processed and analyzed. The second approach uses models to analyze information about the structure. In the latter case, the overall performance of the approach is associated with the accuracy of the model and the information that is used to define it. Although both approaches are widely used, data-driven algorithms are preferred in most cases because they afford the ability to analyze data acquired from sensors and to provide a real-time solution for decision making; however, these approaches involve high-performance processors due to the high computational cost. As a contribution to the researchers working with data-driven algorithms and applications, this work presents a brief review of data-driven algorithms for damage identification in structural health-monitoring applications. This review covers damage detection, localization, classification, extension, and prognosis, as well as the development of smart structures. The literature is systematically reviewed according to the natural steps of a structural health-monitoring system. This review also includes information on the types of sensors used as well as on the development of data-driven algorithms for damage identification.Peer ReviewedPostprint (published version

Damage diagnosis for offshore fixed wind turbines

This paper proposes a damage diagnosis strategy to detect and classify different type of damages in a laboratory offshore-fixed wind turbine model. The proposed method combines an accelerometer sensor network attached to the structure with a conceived algorithm based on principal component analysis (PCA) with quadratic discriminant analysis (QDA). The paradigm of structural health monitoring can be undertaken as a pattern recognition problem (comparison between the data collected from the healthy structure and the current structure to diagnose given a known excitation). However, in this work, as the strategy is designed for wind turbines, only the output data from the sensors is used but the excitation is assumed unknown (as in reality is provided by the wind). The proposed methodology is tested in an experimental laboratory tower modeling an offshore-fixed jacked-type wind turbine. The obtained results show the reliability of the proposed approachPeer ReviewedPostprint (published version

Modelos GEE para el análisis de la evolución de las lesiones acnéicas tratadas con Nadixa

El profesor Bakar Bouadjar del departamento de dermatología (CHU de Bab-el-Oued,Argelia) y Laboratorios Ferrer quieren estudiar la evolución de los pacientes tratados con Nadixa crema 1% para el acné a través de un estudio longitudinal no comparativo. Para el estudio se seleccionaron 30 pacientes con lesiones inflamatorias de acné vulgar con una gravedad leve-moderada. En la semana basal se realizó un recuento de lesiones y en las semanas 2, 4, 8 y 12 se evaluaron la eficacia y la tolerabilidad cutánea. De los pacientes, 22 son mujeres y 7 son hombres. La edad media (± SD) de los pacientes es de 21,7 años (± 4,45) y la duración media (± SD) de la enfermedad es de 48,19 meses (± 25,04). Se ha observado un descenso en el número de lesiones inflamatorias (pápulas, pústulas y nódulos) del -80,6%(IC95% [-81,6% ; -79,9%]). En cambio, el número de lesiones no inflamatorias (quistes, lesiones residuales y cicatrices), se mantiene prácticamente constante en el tiempo. Respecto a la tolerabilidad al medicamento, la probabilidad de tener eritema y prurito disminuye en los individuos a medida que transcurre el tiempo: se pasa de tener una probabilidad del 65,1% (IC95% [50,5% ; 77,3%]) y del 48,7% (IC95% [33,6% ; 64,1%]), respectivamente, en la semana 2, a tener 0,9% (IC95% [0,1% ; 6,7%]) y 0,3% (IC95% [0,02% ; 5,3%]) al final del tratamiento. Sin embargo, la probabilidad de que se produzca descamación y sequedad no decrece de forma clara a medida que avanzan las semanas: se pasa de tener una probabilidad del 44,7% (IC95% [30,8% ; 59,5%]) y del 52% (IC95% [37,6% ; 66,2%]), respectivamente, en la semana 2, a tener 21,8% (IC95% [10,6% ; 39,8%]) y 26,4% (IC95% [13,6% ; 44,9%]) en la semana 12. En conclusión, después de doce semanas de tratamiento con Nadixa, se ha observado una disminución general en las lesiones inflamatorias causadas por el acné. También se ha observado que, en general, la probabilidad de padecer las reacciones adversas eritema y/o prurito disminuye de forma muy rápida, ya que se produce desde las primeras semanas

Disentangling the effects of traffic-related noise and air pollution on blood pressure: indoor noise levels and protections

Outdoor road traffic noise levels are associated with hypertension (HT). Studies on blood pressure (BP) are inconsistent and the true indoor traffic noise exposure may differ due to protections against noise. We analysed the effects of long-term exposure to outdoor and indoor traffic noise levels on HT, systolic (SBP) and diastolic BP (DBP, mmHg), adjusting for outdoor annual average concentrations of near-road traffic-related air pollution (nitrogen dioxide, NO2) among 1926 participants (aged 36-82) from the Catalan REGICOR study. Long-term outdoor residential levels of traffic noise at night (Lnight, in A-weighted dB) and annual averages of NO2 (in µg/m3 ) were estimated at the postal addresses’ façades with a city-specific noise model and a land-use regression model, respectively. Indoor traffic noise was calculated from outdoor noise levels subtracting the attenuations in dB according to reported noise protections. Median noise levels were 56.7 dB outdoors and 27.1 dB indoors. Spearman correlations between outdoor and indoor noise with NO2 were 0.75 and 0.23, respectively. Outdoor noise was only associated with HT (OR=1.19, 95%CI: 1.02, 1.40), whereas there was a suggestive association of indoor noise with both HT (OR=1.06, 95%CI: 0.99, 1.13) and SBP (ß=0.38, 95%CI: -0.08, 0.83) per 5 dB increase in outdoor noise levels. NO2 was also associated with both outcomes after adjustment for indoor noise. Findings for indoor traffic noise levels are more plausible than those for outdoor traffic noise. The use of indoor traffic noise estimates help to disentangle the effects from those of traffic-related air pollution.Postprint (author's final draft

Cross-sectional association between road traffic noise and hypertension in a population-based sample in Girona, Spain (REGICOR-AIR project)

Peer ReviewedPostprint (published version

Transportation noise (in particular railway noise) and blood pressure in REGICOR compared to SAPALDIA

Peer ReviewedPostprint (author's final draft