IMPLEMENTACIÓN DE UN SISTEMA DE PRONÓSTICO Y SU APLICACIÓN A LA DEMANDA DE LOS PRODUCTOS LUBRICANTES FABRICADOS POR UNA EMPRESA (FORECASTING SYSTEM IMPLEMENTATION APPLIED TO THE DEMAND OF THE LUBRICANT PRODUCTS FABRICATED BY AN ENTERPRISE)

Resumen En este trabajo se presenta la implementación de un sistema de pronóstico basado en la combinación de cuatro diferentes métodos. El sistema es empleado para pronosticar las ventas mensuales de 300 productos de una empresa fabricante de lubricantes. Los patrones de venta de cada producto son muy diferentes. Por lo que las series de datos fueron analizados con los métodos de pronósticos: media móvil (MV), suavizado exponencial sencillo (SES), suavizado exponencial doble (DES) y Holt-Winters aditivo (H-WA). Aquí, se muestra que el método de pronóstico idóneo dependerá de las características de la serie de cada producto. Adicionalmente, el promedio de los pronósticos generados por los cuatro métodos proporciona una alternativa interesante como un método único para pronosticar la venta de todos los productos. Finalmente se presentan algunos ejemplos de pronósticos obtenidos con el sistema implementado. Palabras Clave: Periodicidad, pronósticos, series de tiempo, suavizado exponencial, tendencia. Abstract In this work the implementation of a forecasting system based on the combination of four methods is presented. This system is used to forecast the monthly sells of 300 products of a lubricants liquids enterprise. Moreover, the patterns of demand of each product are quite different. Therefore, the time series were analyzed by the forecasting methods: moving average (MV), single exponential smoothing (SES), double exponential smoothing (DES) and the additive Holt-Winters (H-WA). Here, it is shown that the best forecasting method will depends directly on the characteristics of each time series. Additionally, the average of the four forecasting methods provides an interesting alternative since it can be used as unique method for forecasting the demand of all the products. Finally, some forecasting examples obtained with the system are presented. Keywords: Exponential smoothing, forecasting, periodicity, time series, trend

MOS Meets NEMS: The Born of Hybrid Devices

Nowadays, the semiconductor industry is reaching an impasse due to the scaling-down process according to Moore’s Law, initiated back in 1960s, for the Metal-Oxide-Technology in use. To overcome such issue, the semiconductor industry started to foresee novel materials that allow the development of nanodevices with a broad variety of characteristics such as high switching speed, low power consumption, robust, among others; that can overcome the inherent issues for Silicon. A few “exotic materials” appear such as Graphene, MoS2, BN-h, among others. However, the time for the novel technology to be mature is a few decades in the future. To allow the “exotic materials” to mature, the semiconductor industry requires of novel nano-structures that can overcome a few of the issues that Silicon-based technology is facing today. A key alternative is based on hybrid structures. Hybrid structures encompass two dissimilar technologies nano-electromechanical systems with the well known Metal-Oxide-Technology. The hybrid nano-structure provides a broad variety of options to be used in such as transistors, memories and sensors. These hybrid devices can give enough time for the technology based on “exotic materials” to be reliable as Silicon based is

PROPUESTA PARA IMPLEMENTAR UN SENSOR OPTOELECTRÓNICO BASADO EN UN FILTRO ÓPTICO SENSIBLE A LA TEMPERATURA E ÍNDICE DE REFRACCIÓN (PROPOSAL TO IMPLEMENT AN OPTOECLECTRONIC SENSOR BASED ON AN OPTICAL FILTER SENSITIVE TO TEMPERATURA AND REFRACTIVE INDEX)

Resumen En este trabajo se presenta una propuesta para implementar un sensor optoelectrónico basado en un filtro óptico sensible a la temperatura e índice de refracción. Aquí, la respuesta del filtro espectral (un patrón de franjas) es analíticamente modelada y se muestra que la posición de las franjas y su amplitud pico a pico se ven afectados por la temperatura y el índice de refracción externo. Además, se muestra que evaluando la intensidad acumulada relativa de ciertos segmentos del espectro, es posible establecer relaciones casi lineales con ambas variables físicas. Basándonos en estos principios, se presenta la propuesta de un sensor optoelectrónico para medir el índice de refracción de 1–2.5 UIR y la temperatura de 25–56 oC usando un láser sintonizable, un detector de infrarrojo, el filtro espectral fabricado y una etapa electrónica de acondicionamiento y procesamiento de señales. Finalmente, se presenta el modelo matemático del sensor optoelectrónico propuesto. Palabras Clave: Índice de refracción, interferómetro, sensor no dispersivo, sensor optoelectrónico, temperatura. Abstract In this work a proposal to implement an optoelectronic sensor based on an optical filter which is sensitive to temperature and refractive index is presented. Here, the spectral filter response (a fringe pattern) is analytically modeled and it is shown that the position of the fringes and their peak-to-peak amplitude are affected by temperature and the external refractive index. Besides, it is shown that by evaluating the relative accumulated intensity of certain portions of the spectrum, it is possible to establish cuasi linear relationships with both physical variables. Based on these principles, an optoelectronic sensor to measure refractive index from 1–2.5 UIR and temperature from 25–56 oC by using a tunable laser, an infrared photodetector, the fabricated spectral filter and a stage of electronic conditioning and signals processing is proposed. Finally the mathematical model of the proposed optoelectronic sensor is provided. Keywords: Interferometer, non-dispersive sensor, optoelectronic sensor, refractive index, temperature

Analytical method to find the optimal parameters for gas detectors based on correlation spectroscopy using a Fabry-Perot interferometer

Several designs of infrared sensors use a Fabry-Perot Interferometer (FPI) to modulate the incident light. In this work we analyse the particular case where the FPI fringes are matched with very well defined ro-vibrational absorption lines of a target molecule such as CO. In this kind of sensor modulation is induced by scanning the FPI cavity length over one half of the reference wavelength. Here we present an analytical method based on the Fourier transform which simplifies the procedure to determine the sensor response. Furthermore, this method provides a simple solution to finding the optimal FPI cavity length and mirror reflectivity. It is shown that FPI mirrors with surprisingly low reflectivity (<50%) are generally the optimum choice for target gases at atmospheric pressure. Finally experimental measurements and simulation results are presented

Optical gas sensors based on correlation spectroscopy using a Fabry-Perot interferometer

In this work we present an analysis of gas sensors based on correlation spectroscopy with a Fabry-Perot interferometer (FPI). In this technique the spectral FPI transmission fringe pattern is matched with ro-vibrational absorption lines. To produce the cross correlation principle the FPI fringe pattern must be shifted along the frequency axis. Hence as the spectral FPI fringes are equidistant and symmetric therefore the ro-vibrational absorption lines of the target molecule must be almost equidistant. Well resolved ro-vibrational lines with Lorentzian line shapes and with almost equidistant spectral separation are characteristics of most diatomic and linear molecules, i.e. CO2, CO, N2O, and some specific absorptions bands of symmetric top and spherical top molecules eg. NH3, CH4 at one atmosphere pressure. In this work we review two general sensor designs, in the first the FPI it is illuminated with a collimated beam and in the second design the FPI it is illuminated by a converging beam. In the collimated beam design all the rays reaching the FPI have the same angle of incidence whilst in converging beam the incident rays have different angles of incidence. Hence the spectral FPI fringe pattern it is affected by the different angles of incidence and therefore it is essential to consider these effects during the evaluation of the sensor response. A novel analytical method based on the Fourier transform which gives a good insight of the gas sensor design based on correlation spectroscopy with a FPI it is presented which we call the convolution method. The method provides a simple way to evaluate much faster the sensor response, and using the Fourier transform characteristics the functions involved in the mathematical model of the sensor response the optimal cavity length of the FPI can be directly determined and it is shown that if the sensor signal will be recovered by a Phase Sensitivity Detector the optimum mirror reflectivity is 0.41 regardless of the other parameters. Moreover using the convolution method the optimal FPI mirror reflectivity can be quickly evaluated. The method also gives us guidance on selecting the best bandpass filter for the application. In this work we also review the effects of the blackbody converging beam and some possible solutions to minimize the effect of the degraded FPI fringe pattern are proposed. In this case it is important to consider the spurious FPI fringe patterns produced by reflection within the mirrors substrates of FPI mirrors.Finally based on all these knowledge we describe a full methodology to simulate the sensor response. It is important to mention that in our methodology we not use 'fitting parameters’ to adjust the simulated results with experimental measurements. Our experimental measurements strongly support the simulated sensor response obtained with our methodology. Therefore the methodology can be applied to design other gas sensors based on cross correlation spectroscopy with a FPI as a modulator. Moreover it is shown that these sensors present an almost negligible sensitivity to molecules other than the target. Finally based on our simulated and experimental results we can conclude that this sensor design configuration is viable to fabricate commercial gas sensors if the FPI and the detector are integrated within a MEMS structure

An analytical method to find the optimal parameters for gas detectors based on correlation spectroscopy using a Fabry-Perot interferometer

Several designs of infrared absorption based gas detector use a Fabry-Perot Interferometer (FPI) to modulate the incident light. In these systems, generally the FPI's fringes are matched with very well defined rotational absorption lines of a target molecule such as CO2, CO, N2O, CH4, etc. In order to obtain modulation the cavity length of the FPI is scanned over one half of the reference wavelength. In this work, we present a simple analytical method based on the Fourier Transform that describes the performance of these systems. Using this method the optimal reflectivity and optical spacing of the FPI can be determined. Furthermore, the modulated signal generated by the system as a function of the cavity length scan can be calculated by applying the inverse Fourier Transform. Finally, this method describes the underlying reasons why for some filters the background amplitude is severe, and gives guidance on the choice of optimised filters. Our method evaluates the optimal FPI parameters and the modulated signal much faster than the direct numerical computation which is used currently. Simulation results for different molecules in combination with diverse filters shapes are presented, with a comparison to directly computed results

Design of CO, CO₂ and CH₄ gas sensors based on correlation spectroscopy using a Fabry-Perot interferometer

In this paper we present an analytical methodology to evaluate the response of a gas sensor based on correlation spectroscopy using a Fabry-Perot Interferometer (FPI). Here we consider a FPI which is illuminated with a converging beam from a black-body source. It is shown that the optimal FPI cavity length and reflectivity can be easily determined. We designed and tested three different gas sensors (CO, CO2, and CH4) using this methodology. Our numerical results are fully supported by experimental measurements

Method to minimise spurious background signals in gas detectors based on correlation spectroscopy using a Fabry-Perot by bandpass filter shape optimisation

The parasitic background signal produced by gas detectors using a Fabry-Perot Interferometer (FPI) as a modulator is shown to be very sensitive to the infrared band pass filter characteristics. This parasitic signal is generally the feature limiting the sensitivity of such devices. We review this problem, and provide a general approach to filter choice which minimises the background amplitude for this kind of detection system. It is shown that in general filters with very abrupt transitions from the stop to pass band are in fact undesirable, and fortuitously the optimum choice of filter leads to easily realised, low cost designs

Efectividad de la rehidratación oral en niños pequeños con enfermedad diarreica aguda

Se realizó un estudio en el que participaron 100 niños de 0 a 2 años de edad, de 6 consultorios de médicos de la familia pertenecientes al Policlínico Docente "19 de Abril", que fueron llevados a consulta por presentar enfermedad diarreica aguda sin haber recibido antes ningún tratamiento y se les indicaron sales de rehidratación oral. Se obtuvo un predominio en el sexo femenino y en las edades de 4 a 11 meses. La mayor parte presentaba buen estado nutricional entre el 3 y el 10 percentil. Ningún caso necesitó ingreso hospitalario por deshidratación; los 8 casos que ingresaron fueron otras las causas. La mayor parte de los padres conocían las sales de rehidratación oral, pero sólo un grupo menor las usó espontáneamente. La mayoría de los padres poseía un nivel educacional medio.<br>A study was conducted with the participation of 100 children between 0 and 2 years of age from 6 medical offices of the family doctor which belong to the "19 de Abril" teaching polyclinics and who were taken to consultation because of an acute diarrheal disease without treatment. Patients were prescribed oral rehydration salts. Females predominated, as well as the age group of 4-11 months. Most of them presented with a good nutritional status between percentile 3 and 10. None of the patients required hospitalization because of dehydration; 8 cases were admitted due to other causes. Most of the parents knew about oral rehydration salts, but only one group used them spontaneously. The majority of parents had a mid-educational level

EVOLUTION OF 2K FACTORIAL DESIGN: EXPANSION AND CONTRACTION OF THE EXPERIMENTAL REGION WITH A FOCUS ON FUZZY LEVELS

This research presents a novel approach of an evolution of the 2k factorial design (E2kFD) which is based on a fuzzy search heuristic technique. Moreover, this approach allows multiple horizontal and vertical exploration spaces, expanding and contracting the experimental region within the region of operability. It can be achieved by defining a variable position for each point or treatment of study factors in its geometric representation, as an alternative to the conventional 2k factorial design in which fixed positions at the vertices of its geometric representations are defined. In general, the main disadvantage of model-based DoE methods is the requirement for fast and reliable decision making in setting the deterministic value for each level. It is often that the value of the levels is unknown in advance inducing imprecision and vagueness when these are determined by experts based on their heuristic knowledge. For this reason, the proposed method combines the main advantages to use values with uncertainty for each one of the levels and to be able to explore inside and outside of the experimental region to assign variables positions to coded levels, and therefore the method works iteratively. Moreover, in the proposed fuzzy search heuristic technique approach the high and low levels of each factor are considered as linguistic variables. These are classified into three linguistic labels in a simple and clear language as: regular, major and minor which are used as an indicator of strength. A maximum fuzzy operator in the implication and aggregation stages are used to search the highest membership value and their position to assign feasible fuzzy levels as one of the scientific contributions of the present investigation. The method is demonstrated with a simulation, which shows the potential of the proposed approach. Additionally, the traditional 2k factorial and our evolved E2kFD expert designs were validated conducting the experimental tests in a textile company in southern Guanajuato, Mexico. Finally, by comparing the results between the traditional and our proposed designs, it will be shown that better explanation and prediction models for the response variables under study are obtained with the E2kFD proposed design