3 research outputs found
Solución rápida y automática de parámetros hipocentrales para eventos sísmicos, mediante el empleo de técnicas de aprendizaje de máquina
La generación de alertas tempranas para sismos es de gran utilidad, en particular para la ciudad de Bogotá-Colombia, dada su importancia social y económica para el país. Con base en la información de la estación sismológica de El Rosal, la cual es una estación de banda ancha y tres componentes, localizada muy cerca de la ciudad, perteneciente al Servicio Geológico Colombiano (SGC) se desarrolló un modelo de regresión basado en máquinas de vectores de soporte (SVM), con un kernel polinomial normalizado, usando como datos de entrada algunas características de la porción inicial de la onda P empleadas en trabajos anteriores tales como la amplitud máxima, los coeficientes de regresión lineal de los mismos, los parámetros de ajuste logarítmico de la envolvente y los valores propios de la relación de las tres componentes del sismograma. El modelo fue entrenado y evaluado aplicando correlación cruzada, permitiendo llevar a cabo el cálculo de la magnitud y la localización de un evento sísmico con una longitud de señal de tan solo cinco segundos. Con el modelo propuesto se logró la determinación de la magnitud local con una precisión de 0.19 unidades de magnitud, la distancia epicentral con una precisión de alrededor de 11 kilómetros, la profundidad hipocentral con una precisión de aproximadamente 40 kilómetros y el azimut de llegada con una precisión de 45°. Las precisiones obtenidas en magnitud y distancia epicentral son mejores que las encontradas en trabajos anteriores, donde se emplean gran número de eventos para la determinación del modelo y en los demás parámetros hipocentrales son del mismo orden. Este trabajo de investigación realiza un aporte considerable en la generación de alertas tempranas para sismos, no solamente para el país sino para cualquier otro lugar donde se deseen implementar los modelos aquí propuestos y es un excelente punto de partida para investigaciones futuras.Abstract. Earthquake early warning alerts generation is very useful, especially for the city of Bogotá-Colombia, given the social and economic importance of this city for the country. Based on the information from the seismological station “El Rosal”, which is a broadband and three components station, located very near the city that belongs to the Servicio Geológico Colombiano (SGC) a Support Vector Machine Regression (SVMR) model was developed, using a Normalized Polynomial Kernel, using as input some characteristics of the initial portion of the P wave used in earlier works such as the maximum amplitude, the linear regression coefficients of such amplitudes, the logarithmic adjustment parameters of the envelope of the waveform and the eigenvalues of the relationship between the three seismogram components of each band. The model was trained and evaluated by applying a cross-correlation strategy, allowing to calculate the magnitude and location of a seismic event with only five seconds of signal. With the proposed model it was possible to estimate local magnitude with an accuracy of 0.19 units of magnitude, epicentral distance with an accuracy of about 11 km, the hipocentral depth with a precision of approximately 40 km and the arrival back-azimut with a precision of 45°. Accuracies obtained in magnitude and epicentral distance are better that those found in earlier works, where a large number of events were used for model determination, and the other hipocentral parameters precisions obtained here are of the same order. This research work makes a considerable contribution in the generation of seismic early warning alerts, not only for the country but for any other place where proposed models here can be applied and is a very good starting point for future research.Doctorad
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Data cleaning and knowledge discovery in process data
This dissertation presents several methods for overcoming the Big Data challenges, with an emphasis on data cleaning and knowledge discovery in process data. Data cleaning and knowledge discovery is chosen as a main research area here due to its importance from both theoretical and practical points of view.
Theoretical background and recent developments of data cleaning methods are reviewed from four aspects: missing data imputation, outlier detection, noise removal and time delay estimation. Moreover, the impact of contaminated data on model performance and corresponding improvement obtained by data cleaning methods are analyzed through both simulated and industrial case studies. The results provide a starting point for further advanced methodology development.
It is hard to find a universally applicable method for data cleaning since every data set may have its own distinctive features. Thus, we have to customize available methods so that the quality of the data set is guaranteed. An integrated data cleaning scheme is proposed, which incorporates model building and performance evaluation, to provide guidance in tuning the parameters of data cleaning methods and prevent over-cleaning. A case study based on industrial data has been used to verify the feasibility and effectiveness of the proposed new method, during which a partial least squares (PLS) model was built and three univariate data cleaning procedures is tested.
A time series Kalman filter (TSKF) is proposed that successfully handles outlier detection in dynamic systems, where normal process changes often mask the existence of outliers. The TSKF method combines a time series model fitting procedure with a modified Kalman filter to deal with additive outlier (AO) and innovational outlier (IO) detection problems in dynamic process data set. A comparative analysis of TSKF and available methods is performed on simulated and real chemical plant data.
Root cause diagnosis of plant-wide oscillations, as a concrete example of data cleaning and knowledge discovery in the process data, is provided. Plant-wide oscillations can negatively influence the overall control performance of the process and the detection results are often affected by noise at different frequency ranges. To address such a problem, an information transfer method combining spectral envelope algorithm with spectral transfer entropy is proposed to detect and diagnose such oscillations within a specific frequency range, mitigating the effects from measurement noise. The feasibility and effectiveness of the proposed method are verified and compared with available methods through both simulated and industrial case studies.Chemical Engineerin
Machine Learning with Metaheuristic Algorithms for Sustainable Water Resources Management
The main aim of this book is to present various implementations of ML methods and metaheuristic algorithms to improve modelling and prediction hydrological and water resources phenomena having vital importance in water resource management