Bi-criterion optimisation for configuring an assembly supply chain using Pareto ant colony meta-heuristic

An assembly supply chain (SC) is composed of stages that provide the components, assemble both sub-assemblies and final products, and deliver products to the customer. The activities carried out in each stage could be performed by one or more options, thus the decision-maker must select the set of options that minimises the cost of goods sold (CoGS) and the lead time (LT), simultaneously. In this paper, an ant colony-based algorithm is proposed to generate a set of SC configurations using the concept of Pareto optimality. The pheromones are updated using an equation that is a function of the CoGS and LT. The algorithm is tested using a notebook SC problem, widely used in literature. The results show that the ratio between the size of the Pareto Front computed by the proposed algorithm and the size of the one computed by exhaustive enumeration is 90%. Other metrics regarding error ratio and generational distance are provided as well as the CPU time to measure the performance of the proposed algorithm.This work was partially supported by the Spanish Ministerio de Ciencia e Innovación, under the project “Gestión de movilidad eficiente y sostenible, MOVES” with grant reference TIN2011-28336

Estatus de fósforo en aguas superficiales de Puerto Rico: 1989-1997.

Elevated phosphorus (P) concentrations in Puerto Rico's surface waters are suspected to be the primary cause of observed eutrophication.This paper summarizes total P concentrations (TP), historical trends, and relationships between biological and chemical parameters at twenty-two surface water monitoring stations of eleven rivers from 1989 through 1997. Four rivers had median TP concentrations in excess of 0.1 mg P/L (which is considered a threshold limit for eutrophication). The remaining seven rivers, excluding Rio Guajataca, had at least 25% of the sampling episodes exceeding 0.1 mg P/L. When all data (n = 539) were considered, TP in the central 50% of the samples (25 to 75 interquartile range) ranged from 0.04 to 0.29, with mean and median values of 0.30 and 0.09 mg P/L, respectively. Pearson correlation coefficients between TP and fecal coliform bacteria, fecal streptococcal bacteria, and total Kjeidhal nitrogen were 0.38, 0.36, and 0.84, respectively, for all the rivers combined. For rivers with the highest TP concentrations differing relationships between TP and biological and chemical parameters were obtained, thus suggesting that diverse sources were contributing to P loads in rivers. Excluding two stations in Rio Grande de Añasco and Rio Grande de Arecibo, the trend was for TP concentrations to decrease or not change from 1989 to 1997. Approximately half of the variation in P loads in all rivers combined was due to instantaneous hydrologic flow discharge, a finding which corroborates our hypothesis that a number of factors (agricultural non-point sources, background non-point sources, point sources) are contributing to the observed TP concentrations.Los niveles elevados de fósforo (P) están implicados en la eutroficación que se observa en algunos cuerpos de agua superficiales de Puerto Rico. Este trabajo resume las concentraciones de fósforo, tendencias y relaciones entre parámetros biológicos y químicos encontradas en 22 estaciones de monitoreo localizadas en 11 ríos, entre 1989 y 1997. Cuatro ríos tenían concentraciones medianas de fósforo por encima de 0.1 mg P/L (considerado un nivel umbral para la eutroficación de aguas). Las concentraciones de fósforo en los restantes siete ríos, excluyendo el Río Guajataca, excedieron valores de 0.1 mg P/L en 25% de los episodios. Al considerar todos los datos (n = 539), el 50% de las muestras (25 a 75 percentila) tenían un recorrido de 0.04 a 0.29, con medias y medianas de 0.30 y 0.09 mg P/L, respectivamente. Los coeficientes de correlación Pearson, entre fósforo total (PT) y bacterias coliformes fecales, bacterias conformes estreptococales y nitrógeno total Kjeldal fueron 0.38, 0.36 y 0.84, respectivamente, para todos los ríos combinados. Para los ríos con mayores concentraciones de fósforo, se obtuvieron diferentes relaciones entre PT y los parámetros biológicos y químicos seleccionados. Excluyendo dos estaciones en el Río Grande de Añasco y el Río Grande de Arecibo, se observó una disminución o ningún cambio en las concentraciones de fósforo entre 1989 y 1997. Aproximadamente la mitad de la variación en descargas de fósforo en todos los ríos se debió a descarga hidrológica. Estos datos corroboran nuestra hipótesis de que una combinación de factores (fuentes dispersas agrícolas, fuentes dispersas no-agrícolas y fuentes precisas) están aportando fósforo a las aguas superficiales evaluadas

Ricoeur's theory of narrative time and one hundred years of solitude

Paul Ricoeur´s narrative theory of time proposes that we, during our reading, move backwards and forward in narrative time and that “temporality springs forth in the plural unity of future, past and present” (167) . In utilizing his theory of time and the idea of cyclical time as a prominent characteristic in twentieth century literature, I attempt to apply his intriguing theory to an exemplary novel, One Hundred Years of Solitude (1967) by the Colombian Gabriel García Márquez. The essay demonstrates how the circularity of the imaginary travel and the linearity of the quest as such are thus put together. Indeed, time is circular and recurrent rather than rectilinear and progressive in this novel wherein readers are moved between present, past and future time

Proyección de accidentalidad laboral y sus consecuencias, asociadas a la dinámica del mercado laboral en Colombia

59 páginasLa dinámica de los riesgos laborales es muy variable dependiendo los sectores económicos y las clases de riesgo en donde se desarrollen las actividades, ya que en estas se pueden presentar diversas cantidades de accidentes de trabajo y sus consecuencias asociadas como muertes, invalidez o incapacidades permanentes parciales. El análisis de la dinámica del mercado laboral permitiría identificar aquellos sectores económicos y sus respectivas clases de riesgo en las que se podrían presentar los mayores impactos sobre los aspectos asociados a la accidentalidad laboral, de manera que se pueda anticipar la ocurrencia de dichos eventos y fortalecer su respectiva gestión. El presente estudio tiene por objetivo desarrollar un modelo matemático y evaluar su ajuste con los datos históricos de los años 2009 al 2022 para los sectores económicos inmobiliario, construcción, minas, transporte, comercio y agricultura el cual permita proyectar la dinámica del mercado laboral colombiano durante los años 2023 y 2024 y su relación con el crecimiento en el número de trabajadores o empresas. Se utilizó la metodología SEMMA y se desarrolló un modelo matemático basado en el análisis de componentes principales (PCA) y la aplicación de una regresión lineal múltiple a partir de dichos componentes, el cual presentó diferentes ajustes según la variable analizada, el sector económico y la clase de riesgo asociada. Se proyectaron escenarios de crecimiento de los sectores económicos de acuerdo con las dinámicas del mercado laboral actual en Colombia y se evaluaron los cambios en las variables mencionadas, logrando proyectar una visión general de la accidentalidad laboral y sus consecuencias. Finalmente, los modelos mostraron ajustes muy variables, que van desde 0 para variables que nunca tuvieron ocurrencia hasta valores superiores a 0.9, evaluados con la medida del R2. Logrando generar predicciones con un buen nivel de ajuste para algunos sectores económicos y sus clases de riesgo, la cual serviría como insumo para toma de decisiones en materia de riesgos laborales.The dynamics of occupational risks vary greatly depending on economic sectors and the types of risks involved in the activities. This is because varying numbers of workplace accidents and their associated consequences—such as deaths, disabilities, or partial permanent incapacities—can occur in these sectors. Analyzing the dynamics of the labor market would allow for the identification of those economic sectors and their respective risk categories where the greatest impacts on aspects related to workplace accidents could occur. This would enable anticipation of such events and strengthen their respective management. This study aims to develop a mathematical model and evaluate its fit with historical data from 2009 to 2022 for the real estate, construction, mining, transportation, commerce, and agriculture sectors. This model would allow for projecting the dynamics of the Colombian labor market for the years 2023 and 2024 and its relationship with the growth in the number of workers or companies. The SEMMA methodology was used, and a mathematical model based on Principal Component Analysis (PCA) and the application of multiple linear regression from these components was developed. The model showed different levels of fit depending on the variable analyzed, the economic sector, and the associated risk category. Scenarios were projected for the growth of economic sectors based on the current labor market dynamics in Colombia, and changes in the mentioned variables were evaluated, successfully projecting an overall view of workplace accidents and their consequences. Finally, the models showed highly variable fits, ranging from 0 for variables that never occurred to values greater than 0.9, evaluated using the R2 measure. Achieving to generate predictions with a good level of fit for some economic sectors and their risk categories, which would serve as input for decision-making in the area of occupational risks.Maestría en Analítica AplicadaMagíster en Analítica Aplicad

Evaluación termodinámica de la adición de calcio y magnesio a un Ultisol

An experiment was conducted to determine the effects of two calcium sources on the chemistry of an Ultisol at various magnesium levels. A 2 x 4 x 3 complete factorial experimenta! design had two calcium sources [Ca(OH)2, CaSO4]; four calcium levels: control (0 Ca added), 1x Ca (1 meq Ca/meq Al), 2x Ca (2 meq Ca/meq Al), 3x Ca (3 meq Ca/meq Al), and three levels of magnesium: Control (0, Mg), 1x Mg (10% CEC), and 2x Mg (20% CEC). The addition of Ca(OH)2 increased the pH of the soil to approximately the following values: Control - 4.40; 1x Ca - 6.40; 2x Ca - 6.70; 3x Ca - 6.90. This rise in pH more than doubled the sites available for exchangeable cations as pH dependent charges were created. A 20% decrease in exchangeable magnesium was observed without a consequent increase in the levels of magnesium in solution. This finding suggests that a fixation mechanism was precluding magnesium from becoming available, a condition which may create magnesium deficiency problems for the crops grown in these soils.The addition of magnesium to these samples increased their levels of soluble and exchangeable magnesium but had little effect on the overall fixation of magnesium. A decrease in pH in those samples previously limed with Ca(OH)2 caused a dramatic increase in the levels of calcium and magnesium in solution as a result of the release of cations from pH dependent charges in the case of calcium as well as the liberation of the magnesium possibly being held as a Mg-Al precipitate in the case of magnesium.Se realizó un experinemto para determinar el efecto de dos fuentes de calcio en la química de un Ultisol a varios niveles de magnesio. El diseño experimental consistió de un factorial 2 x 4 x 3 con dos fuentes de calcio: [Ca(OH)2, CaSO4], cuatro niveles de calcio: control (0 Ca), 1x Ca (1 meq Ca/meq Al), 2x Ca (2 meq Ca/meq Al) y tres niveles de magnesio: control (0 Mg), 1x Mg (10% del CEC total), 2x Mg (20% del CEC total). La adición de Ca(OH)2, causó un incremento en el pH del suelo en la siguiente proporción: control, 4.40; 1x Ca, 6.40; 2x Ca, 6.70; 3x Ca - 6.90. Este aumento en pH más que duplicó la capacidad de intercambio catiónico del suelo. Sin embargo, el magnesio intercambiable disminuyó en un 20% a consecuencia del incremento en pH. Tampoco se observó ningún incremento en los niveles de magnesio en solución. Los resultados indican que un mecanismo de fijación evitó que el magnesio se hiciera disponible. La adición de magnesio al suelo causó un aumento en los niveles de magnesio intercambiable y en solución, pero no tuvo efecto alguno en el mecanismo de fijación de magnesio. Una reducción en el pH de las muestras previamente encaladas [ Ca(OH)2] causó un aumento considerable en los niveles de calcio y magnesio en solución. Esto se debe a la liberación de ambos cationes de las cargas dependientes de pH, además de la liberación del magnesio previamente fijado

Evaluación termodinámica de la adición de calcio y magnesio a un Ultisol: II CaS04

An experiment was conducted to evaluate the effects of CaS04 additions on the chemical properties of an Ultisol. Four levels of calcium and three levels of magnesium were combined in a 4 x 3 complete factorial experimental design. As expected, the addition of CaS04 resulted in significant increases in the levels of calcium in solution. Furthermore, a decrease in the amount of exchangeable magnesium was observed. This was in turn reflected in an increase in the concentration of magnesium in solution. The correlation between the amount of magnesium in the exchange phase and in solution suggests that the fixation phenomenon frequently observed in limed soils does not occur when CaS04  is used. To evaluate the effect of increases in pH in these samples, NaOH was added a month after CaS04 addition. As in the case of Ca(OH)2, a decrease in the levels of magnesium in solution was observed. This led us to conclude that the presence of SO42- can not prevent the fixation of magnesium, and that aluminum and pH might be the controlling factors of said mechanism.Se condujo un experimento con el propósito de determinar los efectos de la aplicación de CaS04 a un Ultisol de la montaña. Cuatro niveles de calcio y tres niveles de magnesio se combinaron en un diseño experimental factorial completo 4 x 3. La aplicación de CaS04 causó un incremento significativo en los niveles de calcio en solución. Esto estuvo acompañado por una disminución en los niveles de magnesio intercambiable y por un aumento significativo en los niveles de magnesio en solución. La relación entre los niveles de magnesio intercambiable y magnesio en solución sugiere que el mecanismo de fijación de magnesio típico en suelos ácidos que han sido encalados no ocurre si se utiliza CaS04. Para evaluar los efectos de incrementos en pH en estas muestras, le añadimos NaOH a las mismas un mes luego de la aplicación de CaS04. Los aumentos en pH observados estuvieron acompañados de una disminución en los niveles de magnesio en solución similares a los observados con Ca(OH)2. Por tal motivo se concluyó que la presencia de SO4 2- no pudo prevenir la fijación de magnesio y que el aluminio y el pH son los factores que controlan dicho mecanismo

Weak matrix majorization

Given X,Y∈Rn×m we introduce the following notion of matrix majorization, called weak matrix majorization,X≻wYifthereexistsarow- stochasticmatrixA∈Rn×nsuchthatAX=Y,and consider the relations between this concept, strong majorization (≻s) and directional majorization (≻). It is verified that ≻s ⇒ ≻ ⇒ ≻w, but none of the reciprocal implications is true. Nevertheless, we study the implications ≻w ⇒ ≻s and ≻ ⇒ ≻s under additional hypotheses. We give characterizations of strong, directional and weak matrix majorization in terms of convexity. We also introduce definitions for majorization between Abelian families of selfadjoint matrices, called joint majorizations. They are induced by the previously mentioned matrix majorizations. We obtain descriptions of these relations using convexity arguments.Facultad de Ciencias Exacta

Biofloc Technology (BFT): A Tool for Water Quality Management in Aquaculture

Biofloc technology (BFT) is considered the new “blue revolution” in aquaculture. Such technique is based on in situ microorganism production which plays three major roles: (i) maintenance of water quality, by the uptake of nitrogen compounds generating in situ microbial protein; (ii) nutrition, increasing culture feasibility by reducing feed conversion ratio (FCR) and a decrease of feed costs; and (iii) competition with pathogens. The aggregates (bioflocs) are a rich protein-lipid natural source of food available in situ 24 hours per day due to a complex interaction between organic matter, physical substrate, and large range of microorganisms. This natural productivity plays an important role recycling nutrients and maintaining the water quality. The present chapter will discuss some insights of the role of microorganisms in BFT, main water quality parameters, the importance of the correct carbon-to-nitrogen ratio in the culture media, its calculations, and different types, as well as metagenomics of microorganisms and future perspectives

Kernel-Based Framework for Multitemporal and Multisource Remote Sensing Data Classification and Change Detection

The multitemporal classification of remote sensing images is a challenging problem, in which the efficient combination of different sources of information (e.g., temporal, contextual, or multisensor) can improve the results. In this paper, we present a general framework based on kernel methods for the integration of heterogeneous sources of information. Using the theoretical principles in this framework, three main contributions are presented. First, a novel family of kernel-based methods for multitemporal classification of remote sensing images is presented. The second contribution is the development of nonlinear kernel classifiers for the well-known difference and ratioing change detection methods by formulating them in an adequate high-dimensional feature space. Finally, the presented methodology allows the integration of contextual information and multisensor images with different levels of nonlinear sophistication. The binary support vector (SV) classifier and the one-class SV domain description classifier are evaluated by using both linear and nonlinear kernel functions. Good performance on synthetic and real multitemporal classification scenarios illustrates the generalization of the framework and the capabilities of the proposed algorithms.Publicad