Overview of the experimental tests in prototype

Experimental tests in prototype are necessary to understand the dynamic behaviour of the machine during different operating points. Hydraulic phenomena as well as its effect on the structure need to be studied in o rder to avoid instabilities during operation and to extend the life - time of the different components. For this purpose, a complete experimental study of a large Francis turbine prototype has been performed installing several sensors along the machine. Pres sure sensors were installed in the penstock, spiral case, runner and draft tube, strain gauges were installed in the runner, vibration sensors were used in the stationary parts and different electrical and operational parameters were also measured. All the se signals were acquired simultaneously for different operating points of the turbine.Postprint (published version

Explorando el uso de estrategias discursivas y semióticas en la construcción guiada del conocimiento

En este trabajo se exploró el uso diferencial de las estrategias discursivas y semióticas en la construcción guiada del conocimiento en maestras de primaria. Los datos se recogieron del discurso de la maestra en el contexto de la práctica docente, tomando notas y registros durante veinticuatro clases de una hora cada una. Primero, se transcribieron los discursos para después hacer una videoconfrontación con otros investigadores. Se observa que el empleo de la estrategia elicitativa y la intención didáctica en las tres maestras es similar al formular y reformular la participación de los alumnos de manera más o menos rígida, repetitiva, descriptiva e ilustrada. Se evidencian diferencias en el uso del diálogo típico del género de clase. Es necesario considerar el proceso de enseñanza, no como la mera transmisión de saberes, sino como un compromiso de naturaleza social y personal.En aquest treball, es va explorar l'ús diferencial de les estratègies discursives i semiòtiques en la construcció guiada del coneixement en mestres de primària. Les dades es van recollir del discurs de la mestra en el context de la pràctica docent, prenent notes i fent-ne un registre durant vint-i-quatre classes d'una hora cadascuna. Primerament, es van transcriure els discursos per després realitzar una videoconfrontació amb uns altres investigadors. S'hi observa que l'ús de l'estratègia elicitativa i la intenció didàctica en les tres mestres és semblant en el moment de formular i reformular la participació dels alumnes de manera més o menys rígida, repetitiva, descriptiva i il·lustrada. S'hi evidencien diferències en l'ús del diàleg típic del gènere de classe. És necessari considerar el procés d'ensenyament no com a simple transmissió de coneixements, sinó com un compromís de naturalesa social i personal.In this work we have explored how primary teachers differ as they use discursive and semiotic strategies in knowledge-guided construction. Data were collected from three teachers'discourse in the context of her teaching practice by taking notes on 24 different occasions one hour long each. First we transcribed the discourses and then we made a video-confrontation with other researchers. We note that the use of the elicitative strategy and the pedagogical intention is similar among the three teachers as they enact students' participation in a rigid, reiterative, descriptive and illustrated way. Differences are more evident in the use of dialogue as this is adjusted to every single teaching situation. Accordingly we argue that the teaching process needs to be considered not as a simple knowledge transmission, but as a social and personal commitment

Concepciones sobre la enseñanza y difusión del patrimonio en las instituciones educativas y los centros de interpretación. Estudio descriptivo

Desde una perspectiva interdisciplinar (didáctica de las ciencias sociales y didáctica de las ciencias experimentales), se realiza un análisis de concepciones de una muestra estadística de profesores y gestores en relación con el patrimonio, su enseñanza y difusión. Como instrumento para la obtención de la información se ha diseñado un cuestionario, cuyo contenido se ha determinado en función de un sistema de categorías, que se concibe a su vez como instrumento de segundo orden para el análisis de los datos obtenidos. De los resultados destacamos que en el modo de conceptualizar el patrimonio se observa una concepción fragmentaria y reduccionista, en el caso de los profesores, y una visión más global e integradora por parte de los gestores; respecto a la segunda categoría, la escasa relevancia del patrimonio en el currículo, el predominio de una comunicación unidireccional en las actividades que se realizan y el énfasis en las finalidades estrictamente conservacionistas; finalmente, en la relación identidad y tipología patrimonial, una identificación indiferenciada con las diversas manifestaciones patrimoniales en un amplio sector del colectivo de gestores, mientras que en el resto de ambos colectivos se detecta una menor identificación con los elementos etnológicos, estableciéndose una mayor valoración de los naturales y los de carácter histórico-artístico.From a crosscurricular perspective (Social Science Teaching and Experimental Science Teaching) an analysis of beliefs about heritage, its teaching and circulation is aimed. As a means to obtain information, a questionnaire has been devised, whose content has been selected according to a system of categories conceived as a secondary instrument for the analysis of the data obtained. As far as results are concerned, we must point out that there is a tendency to conceptualise heritage in a fragmentary and reductionist way on the part of teachers and a more global and integrative perspective on the part of managers; with respect to the second category, the scant regard for heritage in the curriculum, the ascendancy of a unidirectional communication in the activities and the emphasis in the goals which are mainly conservationalist should be taken into account; finally, in relation to identity and heritage typology, an identification undifferentiated with the varied heritage manifestations is remarkable in a wide sector within the group of managers whereas in the rest of both groups, teachers and managers, there is a tendency to a lesser identification with the ethnological elements, establishing a greater consideration for the natural, historical and artistic items.Desde una perspectiva interdisciplinar (didáctica de las ciencias sociales y didáctica de las ciencias experimentales), se realiza un análisis de concepciones de una muestra estadística de profesores y gestores en relación con el patrimonio, su enseñanza y difusión. Como instrumento para la obtención de la información se ha diseñado un cuestionario, cuyo contenido se ha determinado en función de un sistema de categorías, que se concibe a su vez como instrumento de segundo orden para el análisis de los datos obtenidos. De los resultados destacamos que en el modo de conceptualizar el patrimonio se observa una concepción fragmentaria y reduccionista, en el caso de los profesores, y una visión más global e integradora por parte de los gestores; respecto a la segunda categoría, la escasa relevancia del patrimonio en el currículo, el predominio de una comunicación unidireccional en las actividades que se realizan y el énfasis en las finalidades estrictamente conservacionistas; finalmente, en la relación identidad y tipología patrimonial, una identificación indiferenciada con las diversas manifestaciones patrimoniales en un amplio sector del colectivo de gestores, mientras que en el resto de ambos colectivos se detecta una menor identificación con los elementos etnológicos, estableciéndose una mayor valoración de los naturales y los de carácter histórico-artístico

Numerical framework for transcritical real-fluid reacting flow simulations using the flamelet progress variable approach

An extension to the classical FPV model is developed for transcritical real-fluid combustion simulations in the context of finite volume, fully compressible, explicit solvers. A double-flux model is developed for transcritical flows to eliminate the spurious pressure oscillations. A hybrid scheme with entropy-stable flux correction is formulated to robustly represent large density ratios. The thermodynamics for ideal-gas values is modeled by a linearized specific heat ratio model. Parameters needed for the cubic EoS are pre-tabulated for the evaluation of departure functions and a quadratic expression is used to recover the attraction parameter. The novelty of the proposed approach lies in the ability to account for pressure and temperature variations from the baseline table. Cryogenic LOX/GH2 mixing and reacting cases are performed to demonstrate the capability of the proposed approach in multidimensional simulations. The proposed combustion model and numerical schemes are directly applicable for LES simulations of real applications under transcritical conditions.Comment: 55th AIAA Aerospace Sciences Meeting, Dallas, T

Mutation testing on an object-oriented framework: An experience report

This is the preprint version of the article - Copyright @ 2011 ElsevierContext The increasing presence of Object-Oriented (OO) programs in industrial systems is progressively drawing the attention of mutation researchers toward this paradigm. However, while the number of research contributions in this topic is plentiful, the number of empirical results is still marginal and mostly provided by researchers rather than practitioners. Objective This article reports our experience using mutation testing to measure the effectiveness of an automated test data generator from a user perspective. Method In our study, we applied both traditional and class-level mutation operators to FaMa, an open source Java framework currently being used for research and commercial purposes. We also compared and contrasted our results with the data obtained from some motivating faults found in the literature and two real tools for the analysis of feature models, FaMa and SPLOT. Results Our results are summarized in a number of lessons learned supporting previous isolated results as well as new findings that hopefully will motivate further research in the field. Conclusion We conclude that mutation testing is an effective and affordable technique to measure the effectiveness of test mechanisms in OO systems. We found, however, several practical limitations in current tool support that should be addressed to facilitate the work of testers. We also missed specific techniques and tools to apply mutation testing at the system level.This work has been partially supported by the European Commission (FEDER) and Spanish Government under CICYT Project SETI (TIN2009-07366) and the Andalusian Government Projects ISABEL (TIC-2533) and THEOS (TIC-5906)

Detection of hydraulic phenomena in francis turbines with different sensors

Nowadays, hydropower is demanded to provide flexibility and fast response into the electrical grid in order to compensate the non-constant electricity generation of other renewable sources. Hydraulic turbines are therefore demanded to work under o -design conditions more frequently, where di erent complex hydraulic phenomena appear, a ecting the machine stability as well as reducing the useful life of its components. Hence, it is desirable to detect in real-time these hydraulic phenomena to assess the operation of the machine. In this paper, a large medium-head Francis turbine was selected for this purpose. This prototype is instrumented with several sensors such as accelerometers, proximity probes, strain gauges, pressure sensors and a microphone. Results presented in this paper permit knowing which hydraulic phenomenon is detected with every sensor and which signal analysis technique is necessary to use. With this information, monitoring systems can be optimized with the most convenient sensors, locations and signal analysis techniquesPostprint (published version

Experimental measurements of the natural frequencies and mode shapes of rotating disk-blades-disk assemblies from the stationary frame

Determining the natural frequencies and mode shapes of rotating turbomachinery components from both rotating and stationary reference frames is of paramount importance to avoid resonance problems that could affect the normal operation of the machine, or even cause critical damages in these components. Due to their similarity to real engineering cases, this topic has been experimentally analyzed in the past for disk-shaft assemblies and rotor disk-blades assemblies (bladed-disk or blisk). The same topic is less analyzed for disk-blades-disk assemblies, although such configurations are widely used in centrifugal closed impellers of compressors, hydraulic pumps, pump-turbines, and runners of high head Francis turbines. In this paper, experimental measurements, varying the rotating speed of a disk-blade-disk assembly and exciting the first natural frequencies of the rotating frame, have been performed. The rotating structure is excited and measured by means of PZT patches from the rotating frame and with a Laser Doppler Vibrometer (LDV). In order to interpret the experimental results obtained from the stationary frame, a method to decompose the diametrical mode shapes of the structure in simple diametrical components (which define the diametrical mode shapes of a simple disk) has been proposed. It is concluded that the resonant frequencies detected with a stationary sensor correspond to the ones predicted with the decomposition method. Finally, a means to obtain equivalent results with numerical simulation methods is shown.Postprint (published version

Sensor-based optimized control of the full load instability in large hydraulic turbines

Hydropower plants are of paramount importance for the integration of intermittent renewable energy sources in the power grid. In order to match the energy generated and consumed, Large hydraulic turbines have to work under off-design conditions, which may lead to dangerous unstable operating points involving the hydraulic, mechanical and electrical system. Under these conditions, the stability of the grid and the safety of the power plant itself can be compromised. For many Francis Turbines one of these critical points, that usually limits the maximum output power, is the full load instability. Therefore, these machines usually work far away from this unstable point, reducing the effective operating range of the unit. In order to extend the operating range of the machine, working closer to this point with a reasonable safety margin, it is of paramount importance to monitor and to control relevant parameters of the unit, which have to be obtained with an accurate sensor acquisition strategy. Within the framework of a large EU project, field tests in a large Francis Turbine located in Canada (rated power of 444 MW) have been performed. Many different sensors were used to monitor several working parameters of the unit for all its operating range. Particularly for these tests, more than 80 signals, including ten type of different sensors and several operating signals that define the operating point of the unit, were simultaneously acquired. The present study, focuses on the optimization of the acquisition strategy, which includes type, number, location, acquisition frequency of the sensors and corresponding signal analysis to detect the full load instability and to prevent the unit from reaching this point. A systematic approach to determine this strategy has been followed. It has been found that some indicators obtained with different types of sensors are linearly correlated with the oscillating power. The optimized strategy has been determined based on the correlation characteristics (linearity, sensitivity and reactivity), the simplicity of the installation and the acquisition frequency necessary. Finally, an economic and easy implementable protection system based on the resulting optimized acquisition strategy is proposed. This system, which can be used in a generic Francis turbine with a similar full load instability, permits one to extend the operating range of the unit by working close to the instability with a reasonable safety margin.Postprint (published version

Thresholds for tracing ships' ballast water: An Australian case study

To limit the spread of non-indigenous marine species, ships can be legally required to conduct ballast water exchange (BWE) prior to discharging ballast water. It has been proposed to verify BWE by measuring concentrations of coastal tracers in ballast tanks, which should track their removal. Using 3 Australian ports as case studies (Port Botany, Port Curtis and Port Phillip Bay), each representing a different BWE verification difficulty level, the spatial and temporal variability of chromophoric dissolved organic matter (CDOM) and 3 trace elements (manganese [Mn], barium [Ba] and phosphorus [P]), were measured to assess their utility as tracers of coastal (unexchanged) ballast water. CDOM fluorescence at λex/λem = 320/414 nm (C2*) and 370/494 nm (C3*) and Mn concentrations were significantly higher in ports than in the adjacent Tasman Sea, except near port entrances and at a few sites in Port Botany. Ba concentrations demonstrated the least power to discriminate coastal sources, but P easily discriminated water from mesotrophic Port Phillip Bay. In general, tracers showed greater variation between and within ports, rather than between seasons. Conservative BWE thresholds were calculated to be 1.6 quinine sulphate equivalents for C2*, 0.9 quinine sulphate equivalents for C3*, 1.4 μg l-1 for Mn and 6.9 μg l -1 for Ba. Overall, these thresholds would allow water sourced from eastern Australian ports to be identified as coastal at 92%, 69% and 74% of sites examined using C3*, Mn and Ba, respectively, requiring 71 ± 26%, 54 ± 40% and 59 ± 38% replacement with mid-ocean water to be within ocean baseline concentration ranges. © Inter-Research 2010 · www.int-res.com