Remaining Useful Life Estimation Based on Detection of Explosive Changes: Analysis of Bearing Vibration

The monitoring of condition variables for maintenance purposes is a growing trend amongst researchers and practitioners where decisions are based on degradation levels. The two approaches in Condition-Based Maintenance (CBM) are diagnosing the level of degradation (diagnostics) or predicting when a certain level of degradation will be reached (prognostics). Using diagnostics determines when it is necessary to perform maintenance, but it rarely allows for estimation of future degradation. In the second case, prognostics does allow for degradation and failure prediction, however, its major drawback lies in when to perform the analysis, and exactly what information should be used for predictions. This encumbrance is due to previous studies that have shown that degradation variable could undergo a change that misleads these calculations. This paper addresses the issue of identifying explosive changes in condition variables, using Control Charts, to determine when to perform a new model fitting in order to obtain more accurate Remaining Useful Life (RUL) estimations. The diagnostic-prognostic methodology allows for discarding pre-change observations to avoid contamination in condition prediction. In addition the performance of the integration methodology is compared against adaptive autoregressive (AR) models. Results show that using only the observations acquired after the out-of-control signal produces more accurate RUL estimations

Mar Menor: una laguna singular y sensible. Evaluación científica de su estado.

Este libro recopila las aportaciones que equipos de investigación de la Universidad de Murcia, Universidad Politécnica de Cartagena, Instituto Geológico-Minero de España, Universidad de Alicante, el Instituto Español de Oceanografía y otros organismos hicieron en las Jornadas Científicas del Mar Menor, celebradas en diciembre de 2014.La información recogida en este libro se estructura en dos grandes bloques, uno de Biología y Ecología del Mar Menor (capítulos 1 al 8) y otro de Condiciones fisicoquímicas e impacto de actividades humanas en la laguna (capítulos 9 al 14). El primer bloque resume buena parte de los estudios ecológicos realizados en el Mar Menor, que han servido para mejorar su conocimiento y también para cambiar antiguas asunciones sobre la naturaleza y el funcionamiento de estos ecosistemas lagunares (Capítulo 1). El segundo capítulo muestra que esta laguna alberga en zonas someras de su perímetro hábitats fundamentales para mantener y conservar tanto especies migratorias como residentes, que es necesario conocer para paliar el impacto de las actividades humanas que les afectan. En este sentido la reducción de la carga de nutrientes y contaminantes orgánicos e inorgánicos que fluyen hacia el Mar Menor puede ayudar a preservar la laguna en mejores condiciones, bien sea tratando las escorrentías (plantas de tratamiento, humedales artificiales u otras técnicas) y recuperar este agua para uso agrícola o evitar su descarga en la laguna (Capítulo 3). Estas actuaciones serán clave para la conservación de especies emblemáticas como el caballito de mar (Capítulo 4) y reducir el impacto de las proliferaciones masivas de medusas que se producen en la laguna desde 1993 (Capítulo 5). En este mismo sentido los cambios acaecidos en la laguna han favorecido la incursión de invertebrados marinos alóctonos (Capítulo 6) y han afectado a la respuesta de la dinámica poblacional de las aves acuáticas a distintas escalas (Capítulo 7). Para completar este bloque se ofrece una perspectiva histórica de la importancia que ha tenido la investigación sobre acuicultura realizada en esta laguna, que ha servido de base para su gran desarrollo actual (Capítulo 8). El segundo bloque se inicia con una evaluación del origen y evolución del Mar Menor desde el punto de vista geológico, y evidencia su vulnerabilidad ante el deterioro que puede sufrir la desaparición de la barrera de cierre y/o su colmatación (Capítulo 9). En el Capítulo 10 se describe la relevancia que tiene la interacción de los acuíferos del Campo de Cartagena con la laguna, que se produce no sólo a nivel superficial sino también subterráneo. Esta interacción permite el acceso de nutrientes a la laguna, a pesar de la cierta capacidad de depuración de los humedales que le circundan, y también de metales traza por los aportes de residuos mineros (Capítulo 11). De hecho los metales traza están presentes en los sedimentos de la laguna, y su distribución se ha caracterizado en la columna sedimentaria relacionándola con la granulometría y el contenido de materia orgánica del sedimento (Capítulo 12). Posteriormente se describe la entrada de diversos contaminantes orgánicos, incluyendo pesticidas y fármacos a través de la rambla del Albujón, y su distribución estacional en agua y sedimento de la laguna (Capítulo 13). Este segundo bloque finaliza con el Capítulo 14 en el que se describe la bioacumulación de hidrocarburos aromáticos policíclicos, pesticidas y fármacos en moluscos y peces del Mar Menor, así como los efectos biológicos que la carga contaminante que accede a través de la rambla del Albujón produce en los organismos que allí habitan. El libro concluye con un breve epílogo redactado por los editores de este libro.Versión del edito

In Situ Technological Innovation Diffusion Rate Accuracy Assessment

At present, the accuracy of diffusion rate forecasting, at a macro-level, in the research literature, is nonexistent. This research reveals underlying macro-level trends of diffusion rate assessment using historical technological innovation diffusion data to explore the statistical characteristics of diffusion rate percent-error of the Bass and logistic model time stepped through its lifecycle. A quantitative exploratory data analysis (EDA) based approach was employed to uncover underlying macro-perspective patterns and insights on a technological innovation’s forecasted diffusion rate percent-error using the data of 42 matured U.S. consumer technological innovations. An objective of this effort is to determine the statistical characteristics (mean, median, variance, standard deviation, skewness, and kurtosis) of diffusion rate assessment using the Bass and logistic model at various points in a technological innovation’s lifecycle to reveal underlying directional and associative insights. Specifically, this effort explores the development of macro-perspective knowledge on quantifying the forecasting accuracy of a technological innovation’s diffusion rate using partial diffusion data. Developing such insights and a framework for accessing in situ (real-time) a technological innovation’s diffusion rate percent-error would benefit an organization’s decision makers in maximizing gains and minimizing losses. These insights include identifying whether the Bass and logistic models are more likely to overestimate or underestimate a technological innovation’s diffusion rate when assessed at various points in its diffusion lifecycle. Practitioners can use such information to set resource investment strategies and policies based on risk tolerance and the utility of the weighted outcomes via decision theory tools

A CUSUM control chart for gamma distribution with guaranteed performance

This is the peer reviewed version of the following article: Madrid-Alvarez, H. M., García-Diaz, J. C., & Tercero-Gómez, V. G. A CUSUM control chart for gamma distribution with guaranteed performance. Quality and Reliability Engineering International, which has been published in final form at https://doi.org/10.1002/qre.3464. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.[EN] Even though most control chart developments have revolved around the normal distribution, productive operations, in fact, often use non-normal data, and some even use skewed distributions. This occurs with cycle times and many processes with a single specification limit. Under these conditions, gamma distributions often offer a better characterization where CUSUM schemes provide optimal performance to detect changes of a known in-control (IC) parameter. In practice, gamma parameters have to be estimated, and limited phase I samples have undesirable effects on the phase II average run length (ARL) that has not been examined. To address this situation, this study uses Markovian models to assess the ARL of a CUSUM developed to monitor scale changes when IC parameters are estimated. This paper discusses the conditional ARL performance and proposes an adaptation of a stochastic estimation algorithm to guarantee a minimum performance. IC and out-of-control performance is compared with the conditional performance of a traditional approach where no corrections are made to guarantee a specific behavior. To demonstrate the practical application of this new approach, an implementation was made in a packaging process using multihead weighing machines. Practitioners interested in using reliable monitoring schemes will find, in this proposal, several implementation guidelines such as algorithms and look up tables to facilitate their implementations.Madrid-Alvarez, H.; García-Díaz, JC.; Víctor G. Tercero-Gómez (2023). A CUSUM control chart for gamma distribution with guaranteed performance. Quality and Reliability Engineering International. 1-23. https://doi.org/10.1002/qre.346412

Addressing Concerns about Single Path Analysis in Business Cycle Turning Points: The Case of Learning Vector Quantization

Data-driven approaches in machine learning are increasingly applied in economic analysis, particularly for identifying business cycle (BC) turning points. However, temporal dependence in BCs is often overlooked, leading to what we term single path analysis (SPA). SPA neglects the diverse potential routes of a temporal data structure. It hinders the evaluation and calibration of algorithms. This study emphasizes the significance of acknowledging temporal dependence in BC analysis and illustrates the problem of SPA using learning vector quantization (LVQ) as a case study. LVQ was previously adapted to use economic indicators to determine the current BC phase, exhibiting flexibility in adapting to evolving patterns. To address temporal complexities, we employed a multivariate Monte Carlo simulation incorporating a specified number of change-points, autocorrelation, and cross-correlations, from a second-order vector autoregressive model. Calibrated with varying levels of observed economic leading indicators, our approach offers a deeper understanding of LVQ’s uncertainties. Our results demonstrate the inadequacy of SPA, unveiling diverse risks and worst-case protection strategies. By encouraging researchers to consider temporal dependence, this study contributes to enhancing the robustness of data-driven approaches in financial and economic analyses, offering a comprehensive framework for addressing SPA concerns

A nonparametric economic index to measure the collective effort of national-level economic activities directed towards greater efficiency

For an economic system such as a nation, assessing the efforts of its constituent economic activities that are directed toward greater efficiency, which in aggregate determines the overall efficiency at the national level is important. Such an exercise provides information on which constituent economic activities are underperforming and require attention. This article presents an economic performance index called the Efficiency Effort Index (EE-Index) that measures such efforts of economic activities directed at efficiency improvement. This nonparametric, dimensionless index is computed based on a combination of Leveled-Data-Envelopment-Analysis (LDEA) and Markov Chains (MCs). LDEA compares diverse decision-making units to yield a set of efficiency scores, which are first discretized and then subjected to first-order MC treatment. The EE-Index was computed for a chosen nation and compared with that nation's average relative efficiency (ARE) score, another performance index presented in this study, and GDP per capita. This comparison suggested that the slow growth in the chosen country's GDP coincided with a general declining trend exhibited in the country's efforts and aggregate efficiency achieved by these efforts, measured, respectively, by the EE-Index and the ARE-Index