1,721,968 research outputs found
Epitome de la eloquencia española : arte de discurrir y hablar con agudeza y elegancia en todo genero de assumptos...
No full textFecha de la fe de erratas, 1737Sign. : [calderón], 2[calderón], A-Z, 2A-2I<8
An Innovative Pressing Process by Mechanical Interference Fit for Assembly and Calibration of Fuel Injector
Full text linkIl processo produttivo degli iniettori di combustibile può essere significativamente migliorato con un accurato controllo di posizionamento durante l’assemblaggio per interferenza di componenti sensibili.
Il lavoro di tesi presenta un’innovativa stazione di assemblaggio che combina un cilindro idraulico ed un attuatore piezoelettrico, per raggiungere accuratezze micrometriche nel posizionamento assiale. Il cilindro idraulico esegue grandi corse mente l’attuatore piezoelettrico fornisce l’azione dinamica e l’elevata accuratezza necessaria. La caratterizzazione sperimentale del prototipo di pressa viene presentata, insieme con i fenomeni fisici che ne influenzano le prestazioni. I campioni di prova sono progettati e realizzati per ottenere un’interferenza nota. I sistemi di assemblaggio tradizionali non sono in grado di realizzare accuratezze micrometriche, mentre la nuova stazione di assemblaggio presentata può superare questi limiti grazie all’avanzato algoritmo di controllo sviluppato: quando l’attuatore piezoelettrico è alimentato da un segnale sinusoidale modulato in ampiezza, è possibile raggiungere un’accuratezza di posizionamento di ± 2 μm per forze di inserimento fino a 20 kN.
Le performance ottenute con provini dedicati sono state testate su due casi applicativi reali: un processo di calibrazione a secco di iniettori GDI, nella regione balistica, usando azoto invece di un liquido di test ed il processo di assemblaggio della valvola di controllo a solenoide di un iniettore diesel common rail, che necessita di un’elevata accuratezza geometrica.
Questi studi hanno dimostrato le possibilità del prototipo di stazione di assemblaggio presentato in casi applicativi reali; perciò la pressa può essere inserita in contesti industriali reali, raggiungendo lo scopo della ricerca.The production processes of fuel injectors can be significantly improved by a more accurate positioning control in the assembly of key components by interference fit.
This thesis presents an innovative press-fitting station in the assembly line, that combines a hydraulic cylinder and a piezoelectric actuator to reach micrometric accuracy in axial positioning. The hydraulic cylinder permits a long operational range, while the piezo actuator provides dynamic action and micrometric accuracy. The experimental characterization of the prototype press is presented together with the physical phenomena influencing the overall system performance. The tests are done using cylindrical plugs and sleeves to replicate the insertion of shafts into holes. The test samples are designed and machined to obtain a predefined interference fit. The presented new press-fit station can overcome these limits thanks to the developed advanced control strategy: when the piezo actuator is driven by an amplitude modulated sinusoidal signal, final positioning of ±2 μm is reached insertion forces up to 20 kN.
The remarkable performances obtained using dedicated samples have been then tested for real components in two different use cases: dry calibration process for GDI injector and assembly of a solenoid control valve for state of the art common rail diesel injector.
The first is a cleaner process for calibration of GDI injector in the ballistic region, that uses Nitrogen instead of a liquid working fluid. With this approach a substantially lower error for the injected quantity in the low quantity region can be accomplished. The second application case is an assembly between the pin and the armature of the solenoid control valve of a common rail diesel injector.
These studies have confirmed the possibilities of the press prototype in real application cases; thus, the press can be inserted in real industrial process, achieving the scope of the research
APRENDIZAJE ENTRE IGUALES
No full textRodriguez Rodriguez, Francisco; director de proyecto: Rodríguez Moyano, José Luis2022-2023Máster Universitario en Profesorado de Educación Secundaria Obligatoria y Bachillerato, Formación Profesional y Enseñanza de IdiomasFacultad de Ciencias de la Educació
Recomendaciones para el fortalecimiento de las estrategias comerciales de la agricultura familiar
No full textEl presente capítulo expone aprendizajes y recomendaciones generales generados a partir del estudio de un conjunto de innovaciones de comercialización y agregado de valor realizado en Argentina, Bolivia y España en el marco del proyecto Agricultores Familiares, Innovación y Mercados. El punto de partida es el análisis comparativo de doce experiencias innovadoras que abarcan un conjunto de ferias de la agricultura familiar en Argentina y Bolivia (Ecotambo, en la ciudad de La Paz, Bolivia; y un grupo de ferias en las ciudades de San Miguel de Tucumán, La Plata y Mar del Plata, en Argentina), centros logísticos cooperativos (Madrid Km0 y Far-midable, en Madrid, Sareko y Elikagunea 2.0, en el País Vasco), procesos de agregado de valor y construcción de mercados alternativos (en relación a la producción de queso de cabra en Salta y yerba mate en Misiones, ambos en Argentina), sistemas participativos de garantía (Palos Blancos, en Bolivia) y mercados concentradores (Malvinas Argentinas, en Argentina). Entre las conclusiones se destacan el papel clave que juegan la ampliación del poder de determinar los precios y las condiciones de venta de sus productos, la importancia de las articulaciones y alianzas con otras organizaciones urbanas y de consumidores para dar sostenibilidad a las innovaciones, la existencia de tradiciones asociativas y/o gremiales previas, como así también la existencia de organizaciones cooperativas y tramas de relaciones de reciprocidad consolidadas que sostienen las innovaciones. La presencia de acciones del Estado y políticas públicas es otro de los elementos cuya importancia reflejan los estudios de caso. La transición a la producción agroecológica y los sistemas participativos de garantía cobran particular visibilidad en los estudios, por lo general, en relación con el fortalecimiento de las relaciones con consumidores conscientes. El Covid-19 impulsó, en todos los casos, profundas transformaciones de las modalidades de comercialización que pusieron en evidencia la capacidad de la agricultura familiar y sus organizaciones de replantear la relación con los mercados y enfrentar una crisis de proporciones excepcionales. La cooperación entre actores, las estructuras colaborativas y la construcción de procesos de toma de decisión horizontales, de abajo a arriba, mostraron ser elementos fundamentales en la sostenibilidad de las innovaciones y en el aumento de escala de producción y distribución de los alimentos de la agricultura familiar.Fil: Rodriguez, Francisco. Instituto Nacional de Tecnología Agropecuaria; ArgentinaFil: Cowan Ros, Carlos Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Centro de Estudios Urbanos y Regionales; ArgentinaFil: Garcia, Ariel Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Centro de Estudios Urbanos y Regionales; ArgentinaFil: Viteri, María. Instituto Nacional de Tecnología Agropecuaria; ArgentinaFil: Dumrauf, Sergio. Instituto Nacional de Tecnología Agropecuaria; Argentin
Replication Data for: Sanctions and Imports of Essential Goods: A Closer Look at the Equipo Anova (2021) Results
No full textWe revisit the results of Equipo Anova (2021), who claim to find evidence of an improvement in Venezuelan imports of food and medicines associated with the adoption of U.S. financial sanctions towards Venezuela in 2017. We show that their results are consequence of data coding errors and questionable methodological choices, including the use an unreasonable functional form that implies a counterfactual of negative imports in the absence of sanctions, the omission of data accounting for four-fifths of the country’s food imports at the time of sanctions and incorrect application of regression discontinuity methods. Once these errors are corrected, the evidence of a significant improvement in the level and rate of change in imports of essentials disappears
CCD scanning in photodiode arrays
No full textThis thesis deals with the charge coupling between light sensors and charge-coupled devices in linear imagers. The main aim of this work is the study of the charge transfer mechanism between photodiode and CCD scanner which occurs whilst the sensor is being read out. The physical model is based on MOS theory applied to the optical input stage formed by the photodiode, the MOS switch and the CCD potential well. The analysis of the charge transfer mechanism depends on the previous photodiode history. Therefore the physical phenomena associated with the charge collection due to optical and/or thermal generation of the photosite had to be treated independently. A generalized model has been derived to predict the discharge of p-n step junctions and MOS induced junction as light sensors under any conditions of illumination. The charge transport produced whilst the photodiode injects charge into the CCD is analysed in terms of strong inversion i. e. linear mode, and weak inversion, i. e. subthreshold regimes. From the analysis it has been deduced that the amount of charge stored at the photodiode eventually defines the operating regime. For large charge packets as those-generated at normal light level or at low light levels using long integration times the operation can be considered as purely strong inversion condition. For snail charge packets generated at normal illumination during short integration periods 1'q sets) or at low light levels in periods of time of a few milliseconds, the transfer needs to be treated as a combination of both regimes. At the lower end of the low light level where the amounts of charge collected are comparable to the ones produced by thermal generation, the charge transfer is mostly connected with the subthreshold mode. Experimental tests on P-channel and N-channel S CCD running backwards i. e. from output to input, enabled the sensor diode of the output stage to be characterized as a photodiode. Time measurements for the photodiode recharge during the CCD readout process show reasonable agreement with predictions derived from the theoretical model. The thesis includes the processing of a 10-bit linear imager, its optical and electrical characterization and a novel technique to determine the fast surface state density.</p
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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