Study of the process ofcombustion in a high swirl engine using computational fluiddynamics

La simulación numérica de motores de encendido por chispa presenta incertidumbres que comprometen la fiabilidad de los resultados debido a la interrelación existente de la cinética química y la cinemática del flujo dentro de la cámara de combustión. En este trabajo se evalúa el efecto que tiene el uso de distintos mecanismos de reacción aplicados a un modelo de combustión tipo ecuación G y su interacción con el campo de velocidades dentro de la cámara de combustión de un motor CFR que posee características técnicas especiales (alto swirl y bajas rpm) que permiten estudiar dicho fenómeno. La investigación se realizó numéricamente empleando mecánica de fluidos computacional (CFD), utilizando la ecuación G(con y sin cinética de reacción) como modelo de combustión y el modelo de turbulencia RANS -k − ϵ- RNG. Se compara y valida la simulación contra una prueba experimental que reporta la curva del diagrama indicador. Se estudió la influencia que tienen los mecanismos de reacción y el swirl en el desarrollo del frente de llama y sus variables asociadas dentro de la cámara de combustión. Finalmente se encontraron ligeras discrepancias entre los mecanismos de reacción empleados que podrían ser importantes en simulaciones de motores encendidos por chispa distintos del aquí estudiado. Así mismo se apreció como un aumento en la intensidad del swirl desvía la llama notablemente de los planteamientos teóricos. Las técnicas y códigos actuales requieren ajustar distintos parámetros y por tanto se hace necesaria la validación contra datos experimentales antes de sacar conclusiones de los casos numéricos.The numerical simulation of spark ignition engines has uncertainties that compromise the reliability of the results due to the interrelationship between chemical dynamics and flow kinematics within the combustion chamber. This work evaluated the effect of using different reaction mechanisms applied to a G-equation combustion model and its interaction with the velocity field inside the combustion chamber of a CFR engine, which has special technical characteristics (high swirl and low rpm) that allowed the study of this phenomenon. The research was carried out numerically by computational fluid dynamics (CFD) techniques: using a G-equation combustion model (with and without reaction kinetics) and a RANS -k − ϵ- RNG turbulence model. The numerical simulation was compared and validated against reported experimental pressure indicator diagram. The influence of reaction mechanisms and swirl in the development of the flame front and associated variables within the combustion chamber was studied. Finally slight discrepancies were found between reaction mechanisms used in this study that could be important in simulations of spark ignited engines that are different from the one studied. It was noted that an increase in the intensity swirl yields a flame development deviation from the theoretical models. The current codes and simulation techniques require tuning of various parameters, and thus, the validation against experimental data is needed before drawing conclusions from the numerical cases.Peer Reviewe

Inference of mixed information in Formal Concept Analysis

Negative information can be considered twofold: by means of a negation operator or by capturing the absence of information. In this second approach, a new framework have to be developed: from the syntax to the semantics, including the management of such generalized knowledge representation. In this work we traverse all these issues in the framework of formal concept analysis, introducing a new set of inference rules to manage mixed (positive and negative) attributes.TIN2014-59471-P of the Science and Innovation Ministry of Spain, co-funded by the European Regional Development Fund (ERDF). UNIVERSIDAD DE MÁLAGA. Campus de Excelencia Internacional Andalucía Tech

Extending FuzAtAnalyzer to approach the management of classical negation

FuzAtAnalyzer was conceived as a Java framework which goes beyond of classical tools in formal concept analysis. Specifically, it successfully incorporated the management of uncertainty by means of methods and tools from the area of fuzzy formal concept analysis. One limitation of formal concept analysis is that they only consider the presence of properties in the objects (positive attributes) as much in fuzzy as in crisp case. In this paper, a first step in the incorporation of negations is presented. Our aim is the treatment of the absence of properties (negative attributes). Specifically, we extend the framework by including specific tools for mining knowledge combining crisp positive and negative attributes.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Dirección estratégica de la comunicación en la Iglesia

En los últimos años, un número cada vez mayor de instituciones de la Iglesia ha establecido su propio departamento de comunicación. Crece la conciencia de que su función es importante para dar a conocer la naturaleza y la actividad de la Iglesia en un contexto complejo y plural. Uno de los elementos clave para la eficacia de estas tareas es precisamente la organización del trabajo: una dirección adecuada de la comunicación permite aprovechar al máximo los recursos disponibles (normalmente escasos) y desarrollar un servicio profesional de calidad. El artículo expone las características esenciales de la comunicación institucional de la Iglesia, y propone algunos rasgos que caracterizan la dirección estratégica de sus departamentos de comunicación

Noncommutative Quantum Cosmology

We consider noncommutative quantum cosmology in the case of the low-energy string effective theory. Exacts solutions are found and compared with the commutative case.The Noncommutative quantum cosmology is considered in the case of the low-energy string effective theory. Exacts solutions are found and compared with the commutative case.Comment: Revtex4, 3 pages, 2 figures, to appear in Gen.Rel.Gra

Transgression forms and extensions of Chern-Simons gauge theories

A gauge invariant action principle, based on the idea of transgression forms, is proposed. The action extends the Chern-Simons form by the addition of a boundary term that makes the action gauge invariant (and not just quasi-invariant). Interpreting the spacetime manifold as cobordant to another one, the duplication of gauge fields in spacetime is avoided. The advantages of this approach are particularly noticeable for the gravitation theory described by a Chern-Simons lagrangian for the AdS group, in which case the action is regularized and finite for black hole geometries in diverse situations. Black hole thermodynamics is correctly reproduced using either a background field approach or a background-independent setting, even in cases with asymptotically nontrivial topologies. It is shown that the energy found from the thermodynamic analysis agrees with the surface integral obtained by direct application of Noether's theorem.Comment: 28 pages, no figures. Minor changes in the introduction, final comments and reference

Luxación radiocarpiana con fractura asociada de la apófisis estiloides radial

Presentamos un caso de luxación dorso lateral del carpo con fractura asociada de la estiloides radial en una mujer de 28 años tras accidente de tráfico. No existieron complicaciones neurovasculares. El tratamiento consistió en reducción y fijación de la estiloides radial con agujas de Kirschner. Después de seis meses de evolución la paciente estaba libre de secuelas

Minimum depth required for monitoring the impact of marine culture on benthic fauna

The macrobenthos is an useful tool for studying the impact of marine fish farms on the nearby area. Sampling macrobenthic fauna is both work- and time-intensive, so it is important to determine the minimum optimal volume to be sampled. For this purpose, the present study aimed to find the depth of samples needed to carry out an accurate monitoring of a bottom affected by fish farms. Two different types of bottom (sandy and silty) were sampled in two Galician rias (O Barqueiro and Vigo) in which there are fish farms. In the first 6 cm, we found 86.29 % of the species richness and 84.75 % of fauna density. The results obtained for population structure also show that 6 cm depth samples can be adequate for these kinds of studies.La obtención de la macrofauna bentónica (muestreo, separación e identificación) para evaluar el impacto provocado por los cultivos marinos resulta muy laboriosa y requiere mucho tiempo. Para ahorrar tiempo y esfuerzo, sería de gran ayuda trabajar con un volumen mínimo de muestra. Con este objetivo, este estudio pretende hallar la profundidad mínima que deben tener las muestras para poder llevar a cabo un adecuado seguimiento de los fondos afectados por cultivos marinos. Se muestrearon dos tipos de fondo (arenoso y fangoso) en dos rías gallegas (O Barqueiro y Vigo). En los primeros 6 cm del sedimento se recogió el 86,29 % de la riqueza específica y el 84,75 % en densidad de la fauna. Los resultados obtenidos en cuanto a la estructura de la población señalan que, para este tipo de estudios, son suficientes muestras cuya profundidad alcanza los 6 cm.Instituto Español de Oceanografí

Regularization of odd-dimensional AdS gravity: Kounterterms

As an alternative to the Dirichlet counterterms prescription, I introduce the concept of Kounterterms as the boundary terms with explicit dependence on the extrinsic curvature K_{ij} that regularize the AdS gravity action. Instead of a Dirichlet boundary condition on the metric, a suitable choice of the boundary conditions --compatible with any asymptotically AdS (AAdS) spacetime-- ensures a finite action principle for all odd dimensions. Background-independent conserved quantities are obtained as Noether charges associated to asymptotic symmetries and their general expression appears naturally split in two parts. The first one gives the correct mass and angular momentum for AAdS black holes and vanishes identically for globally AdS spacetimes. Thus, the second part is a covariant formula for the vacuum energy in AAdS spacetimes and reproduces the results obtained by the Dirichlet counterterms method in a number of cases. It is also shown that this Kounterterms series regularizes the Euclidean action and recovers the correct black hole thermodynamics in odd dimensions.Comment: 35+6 pages, 8 references and an appendix added, improved discussion on boundary conditions and geometrical origin of Kounterterms. Version accepted in JHE

Consolidation of massive bone allografts in limb-preserving operations for bone tumours

This study analysed the influence of several factors affecting the consolidation time of 83 massive bone allografts in 79 patients with malignant bone tumours: osteosarcoma 57; Ewing's sarcoma 8; malignant fibrous histiocytoma 3; chondrosarcoma 4; fibrosarcoma 5; and giant cell tumours 2. The mean age of the patients was 19 years and the mean length of the allografts was 18 cm. The minimum follow up was for 12 months. The mean consolidation time for metaphyseal and diaphyseal osteotomies was 6.5 and 16 months respectively. Fifteen diaphyseal osteotomies required autologous cancellous grafting. There were 8 allograft fractures after consolidation. The following factors which might influence consolidation were analysed: age of the host and donor; allograft length and site; type of osteotomy and osteosynthesis; intra-arterial and systemic chemotherapy; intraoperative and external radio-therapy. In diaphyseal osteotomies there were statistically significant differences in consolidation time with the use of systemic chemotherapy, external radiotherapy and the recipient's age