Modeling a complex production line using virtual cells

This chapter presents modeling and simulation of a complex multistage multiproduct production line with four closed loop networks configuration, which also act as a virtual cell. This allows for a greater understanding of the functions within the production line through the simplification of the production flow with the addition of buffers between the cells. Virtual cells are crucial in this instance due to the dynamic configuration, which could help production system designers in optimizing the complex configuration of production

Evaluation of the changes in working limits in an automobile assembly line using simulation

The aim of the work presented in this paper consists of the development of a decision-making support system, based on discrete-event simulation models, of an automobile assembly line which was implemented within an Arena simulation environment and focused at a very specific class of production lines with a four closed-loop network configuration. This layout system reflects one of the most common configurations of automobile assembly and preassembly lines formed by conveyors. The sum of the number of pallets on the intermediate buffers, remains constant, except for the fourth closed-loop, which depends on the four-door car ratio (x) implemented between the door disassembly and assembly stations of the car body. Some governing equations of the four closed-loops are not compatible with the capacities of several intermediate buffers for certain values of variable x. This incompatibility shows how the assembly line cannot operate in practice for x0,97 in a stationary regime, due to the starvation phenomenon or the failure of supply to the machines on the production line. We have evaluated the impact of the pallet numbers circulating on the first closed-loop on the performance of the production line, translated into the number of cars produced/hour, in order to improve the availability of the entire manufacturing system for any value of x. Until the present date, these facts have not been presented in specialized literature. © 2012 American Institute of Physics

The formation of planetary disks and winds: an ultraviolet view

Planetary systems are angular momentum reservoirs generated during star formation. This accretion process produces very powerful engines able to drive the optical jets and the molecular outflows. A fraction of the engine energy is released into heating thus the temperature of the engine ranges from the 3000K of the inner disk material to the 10MK in the areas where magnetic reconnection occurs. There are important unsolved problems concerning the nature of the engine, its evolution and the impact of the engine in the chemical evolution of the inner disk. Of special relevance is the understanding of the shear layer between the stellar photosphere and the disk; this layer controls a significant fraction of the magnetic field building up and the subsequent dissipative processes ougth to be studied in the UV. This contribution focus on describing the connections between 1 Myr old suns and the Sun and the requirements for new UV instrumentation to address their evolution during this period. Two types of observations are shown to be needed: monitoring programmes and high resolution imaging down to, at least, milliarsecond scales.Comment: Accepted for publication in Astrophysics and Space Science 9 figure

New Analytical Methods for teh Study of Wine Aroma. Applications to the Characterizaton of the Headspace Evoluction an Ultra-trace Analysis

Uno de los principales desafíos en la Química del vino es contestar a la pregunta de si la percepción sensorial del mismo puede se explicada o incluso predicha mediante la determinación de su composición química. Aunque conocer la composición en volátiles de la fase líquida del vino es imprescindible, no es suficiente para explicar las notas aromáticas más relacionadas con el espacio decabeza que se encuentra sobre el vino. Está claro que interpretar el papel jugado por los estímulos aromáticos en la percepción global debe implicar otros aspectos, tales como la integración de los procesos perceptuales, los cambios asociados a la liberación de los volátiles y sus modificaciones temporales. Otro aspecto importante es que algunos odorantes impacto pueden dominar el perfil aromático de una variedad de vino particular, incluso encontrándose en niveles de ultratraza requiriendo, por tanto, estrategias de análisis cuantitativo más sensibles. La presente tesis ha caracterizado la liberación de compuestos volátiles y su evolución en el espacio de cabeza de diferentes vinos y también ha investigado el análisis de alquilmetoxipirazinas en vino a niveles ultratraza mediante la aplicación de nuevas metodologías analíticas.Con la consideración de estudiar la composición del espacio de cabeza del vino en condiciones de no-equilibrio, más cercanas a una cata real del vino, en el Capítulo 1 se ha desarrollado un método de análisis basado en la automatización del espacio de cabeza dinámico (DHS) combinado con desorción térmica (TD) y cromatografía gas con detección espectrométrica (GC-MS). Gracias a esta estrategia rápida y dinámica de muestreo, el método proporciona una “instantánea” de la composición de los vapores emanados del vino, ya que permite conocer la concentración de hasta 40 compuestos aromáticos, incluyendo el metanotiol, el dióxido de azufre, los alcoholes de fusel o los fenoles volátiles.En el Capítulo 2, el método DHS validado anteriormente se ha aplicado para evaluar los cambios en los espacios de cabeza del vino y sus cambios temporales, monitorizando los niveles de 34 odorantes emitidos al espacio de cabeza desde 4 vinos diferentes durante 5 puntos en el tiempo. Se han encontrado tres tipos de patrones en cuanto al comportamiento de la evolución de dichos aromas. Estos patrones corresponden a las características físico-químicas de los compuestos volátiles y a las interacciones con los componentes matriciales, lo que sugiere que la predicción del impacto aromático de estos componentes debería incluir una estimación de sus interacciones odorante-matriz en ese vino particular.El Capítulo 3 recoge la aplicación del método DHS, validado previamente, al estudio de las potenciales influencias de los parámetros físicos en la liberación de los compuestos volátiles desde el vino. Estos fenómenos que ocurren durante el periodo de cata incluyen la agitación, evaporación, oxidación y desgasificación. Además, las tendencias de evolución del espacio de cabeza en un vino tinto y otro blanco fueron estudiadas durante 30 min. Durante los experimentos, las características físico-químicas de los compuestos estudiados fueron la clave para explicar su comportamiento en la liberación al espacio de cabezaLos Capítulos 4 y 5 se dedican fundamentalmente al estudio del impacto de las potenciales interacciones compuesto volátil-matriz en el comportamiento de liberación de dichos compuestos, usando el método DHS para detectar los contenidos en un volátil determinado a diferentes tiempos de evaporación. El Capítulo 4 presenta los resultados de la reconstitución de 7 vinos modelo mediante la adición de una mezcla estándar de aromas a vinos desaromatizados con matrices muy diferenciadas. En el Capítulo 5 se aplica la misma estrategia pero al estudio de los cambios en el espacio de cabeza relacionados con la presencia de macromoléculas usadas frecuentemente como aditivos enológicos (diversos polisacáridos y polifenoles).El Capítulo 6 está dedicado al estudio exhaustivo de dos vinos de categoría Premium. En este caso, se combinaron tanto los datos analíticos de los componentes volátiles en fase líquida y fase gas, como los datos obtenidos de un estudio sensorial llevado a cabo por un panel de catadores, en ambos casos en diferentes puntos del proceso de cata. Los datos sensoriales en los diferentes momentos del consumo del vino se correlacionan con la correspondiente concentración en el espacio de cabeza de los compuestos volátiles que son relevantes para cada descriptor de aroma.Las alquilmetoxipirazinas son odorantes muy potentes de muchos alimentos y también en algunos vinos. Normalmente se encuentran presentes en dichos vinos en concentraciones extremadamente bajas. En el Capítulo 7, se desarrolla y valida un nuevo método para la identificación y cuantificación de 3-isopropil- 2-metoxipirazina, 3-sec-butil-2-metoxipirazina y 3-isobutil-2- metoxipirazina. De acuerdo con el método validad, los analitos se extraen de 5 mL de vino usando una barra de extracción SBSE seguido por una desorción térmica y una cromatografía gas multidimensional. El método es automatizable, respetuoso con el medioambiente y proporciona los mejores límites de detección para estos compuestos publicados hasta la fecha (en el rango de las ppq). El método se ha aplicado a la determinación de estos analitos en 111 vinos españoles y franceses elaborados con variedades de uva minoritarias.One of the main challenges in wine chemistry is to answer the question that whether flavor perception can be explained or even predicted by the determination of the chemical composition or not. Although knowing the general volatile composition in the liquid phase of wine is essential, it is not enough for explaining the aroma nuances that are more related to the headspace above the wine. It is clear that interpreting the role played by aroma stimuli in the overall perception needs to involve other aspects, such as the integration of the perceptual processes, the changes associated to the release of volatiles and their temporal modifications. Another important aspect is that some impact odorants can dominate the aroma profile of a particular variety of wine even at ultra-trace levels, requiring more sensitive quantitative strategies. The present thesis has investigated the characterization of the release of volatile compounds and their evolution in the headspace above wines and also has researched the quantitative analysis of ultra-trace alkylmethoxypyrazines in wines by developing new analytical methodologies. With the consideration to study the headspace composition of wine under non-equilibrium conditions that are more closely to the headspace of real wine tasting, an automated dynamic headspace (DHS) method combined with thermal desorption (TD) and gas chromatography-mass spectrometry (GC-MS) has been developed in Chapter 1. Thanks to this fast dynamic sampling strategy, the method could provide a snapshot of the contents in the wine vapors of up to 40 aroma compounds, including methanethiol, sulfur dioxide, aldehydes, fusel alcohols or volatile phenols. In Chapter 2, the validated DHS method has been applied to assess the changes in the wine headspaces with time, monitoring the levels of 34 odorants emitted to the headspace by 4 different wines during five consecutive time points. Three patterns of behavior within the evolution of the aromas were found. These patterns corresponded to the physicochemical characteristics of volatile compounds and the potential interactions with wine matrix components, which suggests that prediction of the aroma impact in these cases should include an estimation of the odorant-matrix interactions in wine. Chapter 3 presents the application of the validated DHS method to study the potential influences of physical parameters on the release of volatile compounds from wine, which occur during tasting period, including agitation, evaporation, oxidation and degasification that could occur during wine drinking. Furthermore, the trends of the headspace evolution of a red and a white wine were studied during a 30 min period. The physicochemical characteristics of the volatile compounds were crucial to explain their release behavior. Chapter 4 and Chapter 5 mainly studied the impact of the potential volatile-matrix interactions on the release behavior of volatile compounds, using the DHS method to detect the contents of given volatile compounds in the headspace within different evaporation times. Chapter 4 reconstituted 7 model wines by adding a standard aroma solution to deodorized wines with distinct matrices. Chapter 5 applied the same strategy but to the study of the headspace changes relating to macromolecules that were oenological additives, such as polysaccharides and polyphenols. Chapter 6 was devoted to the comprehensive study of two premium category wines. In this case, both the analytical data of the volatile components in the liquid phase and those of the headspace at different time points were combined with a complete simultaneous sensory study carried out by a panel of tasters. The sensory data at different moments of wine tasting were correlated with the corresponding concentration data in the headspace of volatile compounds that were relevant to each aroma descriptor. Alkylmethoxypyrazines are potent odorants in many food products, as well as in wines. Usually, they are presented at extremely low concentration levels. In Chapter 7, a new method for the identification and quantitation of 3-isobutyl-2-methoxypyrazine, 3-isopropyl-2-methoxypyrazine and 3-sec-butyl-2-methoxypyrazine has been developed and applied to wine. According to the validated method, the analytes were extracted from 5 mL of wine using stir-bar sorptive extraction followed by thermal desorption and multidimensional gas chromatography-mass spectrometry analysis in a single oven. The method is not only automatable and environmentally friendly but also provides the best limits of detection for these compounds published to date. The method has been applied to the analysis of 111 Spanish and French wine samples produced with minor and rare grape varieties.<br /

Evaluation of a two-phase extraction system of carbohydrates and proteins from chlorella vulgaris utex 1803

Microalgae are a valuable source of high-value products and biofuels, however the high-energy cost required for the extraction of their metabolites has kept questioning on possible industrial upgrading. The aim of this study was to evaluate the effect of temperature, solvent/biomass, NaOH concentration and thermal pretreatment of the biomass in a 2-cycle carbohydrate and protein extraction system. Results shown that best conditions for carbohydrates extraction are achieved at a solvent concentration of 3.67 M, 55°C and a solvent/biomass ratio of 30mL/g. On the other side, the best conditions for protein were 3 M, 85°C and 45 mL/g. The efficiencies achieved under these conditions were 95% for carbohydrates and 98% for proteins. Using the best extraction conditions for each metabolite a thermal pre-treatment was performed at 25°C, 75°C and 105°C. Results indicate that highest efficiencies were achieved with dry biomass pretreated at 105°C, with values of 95% for carbohydrates and 98% for proteins

Latitudinal gradients of galactic cosmic rays during the 2007 solar minimum

Ulysses, launched in 1990 October in the maximum phase of solar cycle 22, completed its third out-of-ecliptic orbit in 2008 February. This provides a unique opportunity to study the propagation of cosmic rays over a wide range of heliographic latitudes during different levels of solar activity and different polarities in the inner heliosphere. Comparison of the first and second fast latitude scans from 1994 to 1995 and from 2000 to 2001 confirmed the expectation of positive latitudinal gradients at solar minimum versus an isotropic Galactic cosmic ray distribution at solar maximum. During the second scan in mid-2000, the solar magnetic field reversed its global polarity. From 2007 to 2008, Ulysses made its third fast latitude scan during the declining phase of solar cycle 23. Therefore, the solar activity is comparable in 2007-2008 to that from 1994 to 1995, but the magnetic polarity is opposite. Thus, one would expect to compare positive with negative latitudinal gradients during these two periods for protons and electrons, respectively. In contrast, our analysis of data from the Kiel Electron Telescope aboard Ulysses results in no significant latitudinal gradients for protons. However, the electrons show, as expected, a positive latitudinal gradient of ~0.2% per degree. Although our result is surprising, the nearly isotropic distribution of protons in 2007-2008 is consistent with an isotropic distribution of electrons from 1994 to 1995

The role of the agricultural sector in Ghanaian development: a multiregional SAM-based analysis

Ghana shows remarkable differences in employment and welfare between the southern and northern regions. The promotion of policy focus on the development of the northern regions requires the elaboration of specific databases describing the regional economies. Hence, this work outlines the construction of a Social Accounting Matrix (SAM) for Ghana for the year 2015 with a high disaggregation of sectors, household income groups and education levels across 10 administrative regions. Linear multisectoral models have been applied to this SAM to estimate socio-economic impacts of potential final demand policies down to a regional level in the Ghanaian economy. Further on, the structural path analysis is used to investigate the role played by different agriculture commodities in transmitting income to different types of households. The results allow for an identification of the most suitable sectors to be promoted due to their ability to generate the highest increases in output, employment and value added in the rest of the economy, as well as those with a significant impact on household income generation. As a result, the primary sector will play a key role in the economic and employment growth of the country. Notably, sorghum and millet, pulses, tobacco, cotton and fibres can be considered favourable crops for development in the Northern region

Estudio del sistema de marcapasos auriculares en el corazón del perro

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