Fault diagnosis for an MSF desalination plant by using Bayesian networks

This work outlines the development of a fault diagnostic system for an MSF (multi-stage flash) desalination plant by using BNs (Bayesian networks). This diagnostic system processes the plant data to determine whether the process state is normal or not. In the latter case, the diagnostic system determines the cause of the abnormal process state; i.e., it finds out which is the fault that is affecting the supervised process. A BN is a graphical model that encodes probabilistic relationships among variables of interest. When used in conjunction with statistical techniques, the graphical model has several advantages for data analysis. A BN readily handles situations where some data entries are missing. This paper determines both the structure and parameters of a BN intended for a diagnostic system. The implemented system is evaluated by using a dynamic simulator, which was developed for a real MSF desalination plant. Besides, the diagnostic system performance is compared with the performances of two other diagnostic systems. The obtained results show some advantages for the BN based diagnostic system.Fil: Tarifa, Enrique Eduardo. Universidad Nacional de Jujuy; ArgentinaFil: Álvaro, F. Núñez. Universidad Nacional de Jujuy; ArgentinaFil: Franco, Samuel. Universidad Nacional de Jujuy; ArgentinaFil: Mussati, Sergio Fabian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo y Diseño. Universidad Tecnológica Nacional. Facultad Regional Santa Fe. Instituto de Desarrollo y Diseño; Argentin

Formulación de un examen académico óptimo

The aim of this paper is to formulate an optimal academic exam for a given subject. To do this, the probability is first modelled of a student passing the exam according to the number of units he studies and the professor evaluates. That simulation model is developed by performing a probabilistic analysis. An optimal exam is then defined as the one that awards the grade that the student deserves. Therefore, in an optimal exam, approve those who deserve to approve, and disapprove those that do not deserve to approve. Besides, this exam must respect the limitations of time and effort that the professor imposes. Based on this definition and using the simulation model, an INLP type optimization model is formulated. This optimization model determines the number of units the professor must evaluate to maximize the probability of getting an optimal exam.El objetivo de este trabajo es formular un examen académico óptimo para una materia dada. Para ello, primero, se modela la probabilidad de que un estudiante apruebe el examen en función del número de unidades que estudia y de las que el profesor evalúa. Ese modelo de simulación es desarrollado realizando un análisis probabilístico. Un examen óptimo es luego definido como aquel que asigna la nota que el estudiante merece. Por lo tanto, en un examen óptimo, aprueban quienes merecen aprobar, y desaprueban quienes no merecen aprobar. Además, el examen debe respetar las limitaciones de tiempo y esfuerzo que el profesor impone. En base a esta definición y usando el modelo de simulación, se formula un modelo de optimización del tipo INLP. Este modelo de optimización determina el número de unidades que el profesor debe evaluar para maximizar la probabilidad de conseguir un examen óptimo.Facultad de Informátic

Formulación de un examen académico óptimo

The aim of this paper is to formulate an optimal academic exam for a given subject. To do this, the probability is first modelled of a student passing the exam according to the number of units he studies and the professor evaluates. That simulation model is developed by performing a probabilistic analysis. An optimal exam is then defined as the one that awards the grade that the student deserves. Therefore, in an optimal exam, approve those who deserve to approve, and disapprove those that do not deserve to approve. Besides, this exam must respect the limitations of time and effort that the professor imposes. Based on this definition and using the simulation model, an INLP type optimization model is formulated. This optimization model determines the number of units the professor must evaluate to maximize the probability of getting an optimal exam.El objetivo de este trabajo es formular un examen académico óptimo para una materia dada. Para ello, primero, se modela la probabilidad de que un estudiante apruebe el examen en función del número de unidades que estudia y de las que el profesor evalúa. Ese modelo de simulación es desarrollado realizando un análisis probabilístico. Un examen óptimo es luego definido como aquel que asigna la nota que el estudiante merece. Por lo tanto, en un examen óptimo, aprueban quienes merecen aprobar, y desaprueban quienes no merecen aprobar. Además, el examen debe respetar las limitaciones de tiempo y esfuerzo que el profesor impone. En base a esta definición y usando el modelo de simulación, se formula un modelo de optimización del tipo INLP. Este modelo de optimización determina el número de unidades que el profesor debe evaluar para maximizar la probabilidad de conseguir un examen óptimo.Facultad de Informátic

Synthesis of graphenic nanomaterials by decomposition of methane on a Ni-Cu/biomorphic carbon catalyst. Kinetic and characterization results

This work addresses the preparation and application of the synthesis of graphene in Ni-Cu catalysts supported on carbonaceous materials. The catalysts have been prepared by a biomorphic mineralization technique which involves the thermal decomposition, under reductive atmosphere, of commercial cellulose previously impregnated with the metallic precursors. The characterization results indicate that the preparation method leads to the formation of carbonaceous supports with a moderate microporosity (ca. 33% pore volume) and adequate surface area (343 m2/g), maintaining the original external texture. The catalytic performance of these materials was previously tested in liquid phase reactions (Zampieri et al., 2007 [7]). In order to extend the use of these catalysts, in this work we present a study corresponding to a gas phase reaction: the synthesis of graphenic nanomaterials by catalytic decomposition of methane (CDM). The influence of the reaction temperature and of the feed composition (i.e.%CH4 and%H2) has been studied. The graphenic nanomaterials obtained after reaction were characterized by nitrogen adsorption-desorption isotherms, Raman spectroscopy and transmission electron microscopy (TEM). The results indicate that the carbonaceous nanomaterial with the highest quality is obtained operating at 950 °C and feeding 28.6% of CH4 and 14.3% of H2. The evolution of the carbon mass during the reaction time was analysed using a phenomenological kinetic model that takes into account the main stages involved during the formation of carbonaceous nanomaterials (NCMs). The results obtained from the kinetic model along with the characterization results enable the influence of the operating variables on each stage of the carbonaceous nanomaterial formation to be discerned

Hydrophobic RWGS catalysts: Valorization of CO2-rich streams in presence of CO/H2O

Nowadays, the majority of the Reverse Water Gas Shift (RWGS) studies assume somehow model feedstock (diluted CO2/H2) for syngas production. Nonetheless, biogas streams contain certain amounts of CO/H2O which will decrease the obtained CO2 conversion values by promoting the forward WGS reaction. Since the rate limiting step for the WGS reaction concerns the water splitting, this work proposes the use of hydrophobic RWGS catalysts as an effective strategy for the valorization of CO2-rich feedstock in presence of H2O and CO. Over Fe-Mg catalysts, the different hydrophilicities attained over pristine, N- and B-doped carbonaceous supports accounted for the impact on the activity of the catalyst in presence of CO/H2O. Overall, the higher CO productivity (4.12 μmol/(min·m2)) attained by Fe-Mg/CDC in presence of 20 % of H2O relates to hindered water adsorption and unveil the use of hydrophobic surfaces as a suitable approach for avoiding costly pre-conditioning units for the valorization of CO2-rich streams based on RWGS processes in presence of CO/H2O

Formulación de un examen académico óptimo

The aim of this paper is to formulate an optimal academic exam for a given subject. To do this, the probability is first modelled of a student passing the exam according to the number of units he studies and the professor evaluates. That simulation model is developed by performing a probabilistic analysis. An optimal exam is then defined as the one that awards the grade that the student deserves. Therefore, in an optimal exam, approve those who deserve to approve, and disapprove those that do not deserve to approve. Besides, this exam must respect the limitations of time and effort that the professor imposes. Based on this definition and using the simulation model, an INLP type optimization model is formulated. This optimization model determines the number of units the professor must evaluate to maximize the probability of getting an optimal exam.El objetivo de este trabajo es formular un examen académico óptimo para una materia dada. Para ello, primero, se modela la probabilidad de que un estudiante apruebe el examen en función del número de unidades que estudia y de las que el profesor evalúa. Ese modelo de simulación es desarrollado realizando un análisis probabilístico. Un examen óptimo es luego definido como aquel que asigna la nota que el estudiante merece. Por lo tanto, en un examen óptimo, aprueban quienes merecen aprobar, y desaprueban quienes no merecen aprobar. Además, el examen debe respetar las limitaciones de tiempo y esfuerzo que el profesor impone. En base a esta definición y usando el modelo de simulación, se formula un modelo de optimización del tipo INLP. Este modelo de optimización determina el número de unidades que el profesor debe evaluar para maximizar la probabilidad de conseguir un examen óptimo.Facultad de Informátic

Performance of AISI 316L-stainless steel foams towards the formation of graphene related nanomaterials by catalytic decomposition of methane at high temperature

This work explores the preparation of graphene-related materials (GRMs) grown on stainless steel foams via catalytic decomposition of methane (CDM). The main active phases for the reaction are the Fe nanoparticles segregated from the stainless-steel after the activation stage of the foam. The effect of the feed composition and reaction temperature has been studied in order to maximize the productivity, stability and selectivity to GRMs. The maximum productivity attained was 0.116 gC/gfoam h operating at 950 °C with a feed ratio of CH4/H2 = 3 (42.9 %CH4:14.3 %H2). The carbonaceous nanomaterials (CNMs) obtained were characterized by X-Ray diffraction, Raman spectroscopy and by transmission and scanning electron microscopy. The parameters of the kinetic model developed are directly related to the relevant stages of the process, including carburization, diffusion-precipitation and deactivation-regeneration. The balance among these sequential stages determines the overall performance of the activated foam. In conditions of rapid carburization of the Fe NPs (pCH4 > 14 %), the productivity to CNMs is favoured, avoiding an initial deactivation of the active sites by fouling with amorphous carbon. After a rapid carburization, the selectivity to the different CNMs is governed by the ratio CH4/H2, and mainly by the temperature. Thus, the formation of GRMs, mainly Few Layer Graphene (FLG) and even graphene, is favoured at temperatures above 900 °C. At lower temperatures, carbon nanotubes are formed

Heterogeneous combustion processes under microgravity conditions

An experimental programme on flame spreading over the surface of PMMA (plexiglass) samples has been conducted under microgravity conditions in the NASA KC-135 aircraft laboratory. A few experiments (three) were conducted in 1986 under the preceding contract no. 6284/85/F/FL, but the largest part of the experimental programme has been carried out under the present contract in two parabolic flights campaigns. A total of 36 experiments were performed, most of them successful. From the results of these experiments the flame-spreading velocities over PMMA samples have been obtained, as well as their laws of variation with pressure and mixture composition. Both cylindrical (axial symmetry) and flat (bidimensional symmetry) samples have been investigated

Rate effect in inclined fibre pull-out for smooth and hooked-end fibres: a numerical study

Based on a numerical model to simulate the static behaviour of a smooth fibre extracted from a cementitious matrix, a rate dependent friction law, widely used in earthquake engineering for steady-state slip phenomena, is proposed to capture the rate effect observed in dynamic pull-out tests for both smooth and hooked-end fibres. After calibrating the friction coefficients with the experimental results of smooth fibres, the model is subsequently applied to predict the pullout behaviour of both smooth and hooked-end fibres at different inclination angles (0∘, 30∘ and 60∘) loaded at three different velocities (0.01, 0.1 and 1 mm/s). The global tendency of all the pull-out curves was captured, fibre’s cross sectional deformations were also reproduced remarkably well. Moreover, the developed model helps to cast light on the different mechanisms related to the pull-out process.Ministerio de Ciencia, Innovación y Universidades, Spain, through the projects BIA2015-68678-C2-1-R and RTC-2017-6736-3, is acknowledged. Elisa Poveda appreciates the funding from the International Campus of Excellence CYTEMA, as well as, the University of Castilla-La Mancha, throughout Ayudas para estancias en universidades en el extranjero en 2019 en el ámbito del plan propio de investigación susceptibles de co-financiación por el Fondo FEDER, Programa 010100021 to fund her stay in the University of Minho during 2018 and 2019, respectively. Manuel Tarifa acknowledges the financial support from the Department of Applied Mechanics and Project Engineering, UCLM (2018), and from the Programa propio de I+D+i de la Universidad Politécnica de Madrid para realizar estancias de investigación internacional igual o superior a un mes (2019), with the same purpose. The last two authors acknowledge the support provided by the project ICoSyTec (POCI-01-0145-FEDER-027990) financed by FCT and co-funded by FEDER through the Operational Competitiveness and Internationalization Programme (POCI). The authors thank BEKAERT for the supply of fibre

Aula virtual en Moodle: cambio de paradigma educativo

En este trabajo se presenta la experiencia obtenida al implementar, en forma gradual, un aula virtual para la materia “S imulación y Optimización”. Esta materia pertenece al último año de la carrera Ingeniería Química de la Facultad de Ingeniería de la UNJu. Con la introducción del aula virtual, el dictado de la materia se modificó para adoptar una modalidad b- learning. Esto demandó un gran esfuerzo por parte de la cátedra; pero los resultados obtenidos en cuanto al rendimiento académico de los estudiantes son notables: en el primer cuatrimestre de 2014, de los 15 inscriptos, 9 promo- cionaron la materia, 5 regularizaron la materia sin necesidad de recuperar ningún parcial, sólo se registró un abandono.Eje: Educación en TecnologíaRed de Universidades con Carreras en Informática (RedUNCI