Continuation and stability of rotating waves in the magnetized spherical Couette system: Secondary transitions and multistability

Rotating waves (RW) bifurcating from the axisymmetric basic magnetized spherical Couette (MSC) flow are computed by means of Newton-Krylov continuation techniques for periodic orbits. In addition, their stability is analysed in the framework of Floquet theory. The inner sphere rotates whilst the outer is kept at rest and the fluid is subjected to an axial magnetic field. For a moderate Reynolds number ${\rm Re}=10^3$ (measuring inner rotation) the effect of increasing the magnetic field strength (measured by the Hartmann number ${\rm Ha}$) is addressed in the range ${\rm Ha}\in(0,80)$ corresponding to the working conditions of the HEDGEHOG experiment at Helmholtz-Zentrum Dresden-Rossendorf. The study reveals several regions of multistability of waves with azimuthal wave number $m=2,3,4$, and several transitions to quasiperiodic flows, i.e modulated rotating waves (MRW). These nonlinear flows can be classified as the three different instabilities of the radial jet, the return flow and the shear-layer, as found in previous studies. These two flows are continuously linked, and part of the same branch, as the magnetic forcing is increased. Midway between the two instabilities, at a certain critical ${\rm Ha}$, the nonaxisymmetric component of the flow is maximum.Comment: Published in the Proceedings of the Royal Society A journal. Contains 3 tables and 12 figure

Open Apps: Opening Teaching Experiences and Applications

The Universitat Oberta de Catalunya (Open University of Catalonia, UOC) is an online university that makes extensive use of information and communication technologies to provide education. Ever since its establishment in 1995, the UOC has developed and tested methodologies and technological support services to meet the educational challenges posed by its student community and its teaching and management staff. The know-how it has acquired in doing so is the basis on which it has created the Open Apps platform, which is designed to provide access to open source technical applications, information on successful learning and teaching experiences, resources and other solutions, all in a single environment. Open Apps is an open, online catalogue, the content of which is available to all students for learning purposes, all IT professionals for downloading and all teachers for reusing. To contribute to the transfer of knowledge, experience and technology, each of the platform¿s apps comes with full documentation, plus information on cases in which it has been used and related tools. It is hoped that such transfer will lead to the growth of an external partner network, and that this, in turn, will result in improvements to the applications and teaching/learning practices, and in greater scope for collaboration. Open Apps is a strategic project that has arisen from the UOC's commitment to the open access movement and to giving knowledge and technology back to society, as well as its firm belief that sustainability depends on communities of interest.La Universitat Oberta de Catalunya (UOC) es una universidad en línea que realiza un uso intensivo de las tecnologías de la información y la comunicación para proporcionar una educación y aprendizaje a lo largo de la vida. Des de sus inicios la universidad ha desarrollado y testeado metodologías y tecnologías con el objetivo de proporcionar soluciones a los retos de aprendizaje y docentes ofrecidos por la comunidad de estudiantes, académicos y personal de gestión. Fundamentado en este saber hacer, nace la plataforma OpenApps con la finalidad principal de poner a disposición de la comunidad la experiencia acumulada en la UOC durante más de 15 años en docencia, aprendizaje y gestión para que pueda ser aplicado, adaptado o evolucionado por terceros. En este artículo se presentan las características esenciales para que una innovación pueda formar parte de esta plataforma institucional, las especificaciones y usuarios de la plataforma, la finalidad del servicio y las futuras líneas de trabajo.La universitat Oberta de Catalunya (UOC) és una universitat en línia que fa un ús intensiu de les tecnologies de la informació i la comunicació per proporcionar una educació i aprenentatge al llarg de la vida. Des dels seus inicis la universitat ha desenvolupat i testejat metodologies i tecnologies amb l'objectiu de proporcionar solucions als reptes d'aprenentatge i docents oferts per la comunitat d'estudiants, acadèmics i personal de gestió. Basat en aquest saber fer, neix la plataforma OpenApps amb la finalitat principal de posar a disposició de la comunitat l'experiència acumulada a la UOC durant més de 15 anys en docència, aprenentatge i gestió, perquè es pugui aplicar, adaptar o desenvolupar per tercers. En aquest article es presenten les característiques essencials perquè una innovació pugui formar part d'aquesta plataforma institucional, les especificacions i usuaris de la plataforma, la finalitat del servei i les futures línies de treball

Investing in the BMW group. What do we have to know?

Universitat de Barcelona, Facultat d'Economia i Empresa, Assignatura: Anàlisi d'Estats Comptables, Curs: 2012-2013, Director: Jordi Marti PidelaserraIt’s not easy thinking about one interesting firm that allows us to work out with all the necessary information needed to develop some interesting lines, us we will do in this work. The BMW Group – one of Germany’s largest industrial companies – is one of the most successful car and motorcycle manufacturers in the world. With BMW, MINI and Rolls-Royce, the BMW Group owns three of the strongest premium brands in the automobile industry. The vehicles manufactured by BMW set the highest standards in terms of aesthetics, dynamics, technology and quality, borne out by the company’s leading position in engineering and innovation. In addition to its strong position in the motorcycles market with the BMW and Husqvarna brands, the BMW Group also offers a successful range of financial services

El sistema electoral vigent, expressa fidelment l'opinió política del nostre país?

Una anàlisi des del punt de vista psicològic de les dificultats i limitacions que també presenta el nostre sistema electora

The Multivariate Extension of the Lomb-Scargle Method

The common methods of spectral analysis for multivariate (n-dimensional) time series, like discrete Frourier transform (FT) or Wavelet transform, are based on Fourier series to decompose discrete data into a set of trigonometric model components, e. g. amplitude and phase. Applied to discrete data with a finite range several limitations of (time discrete) FT can be observed which are caused by the orthogonality mismatch of the trigonometric basis functions on a finite interval. However, in the general situation of non-equidistant or fragmented sampling FT based methods will cause significant errors in the parameter estimation. Therefore, the classical Lomb-Scargle method (LSM), which is not based on Fourier series, was developed as a statistical tool for one dimensional data to circumvent the inconsistent and erroneous parameter estimation of FT. The present work deduces LSM for n-dimensional data sets by a redefinition of the shifting parameter \tau, to maintain orthogonality of the trigonometric basis. An analytical derivation shows, that n-D LSM extents the traditional 1D case preserving all the statistical benefits, such as the improved noise rejection. Here, we derive the parameter confidence intervals for LSM and compare it with FT. Applications with ideal test data and experimental data will illustrate and support the proposed method.Comment: to be publishe

Fluid Communities: A Competitive, Scalable and Diverse Community Detection Algorithm

We introduce a community detection algorithm (Fluid Communities) based on the idea of fluids interacting in an environment, expanding and contracting as a result of that interaction. Fluid Communities is based on the propagation methodology, which represents the state-of-the-art in terms of computational cost and scalability. While being highly efficient, Fluid Communities is able to find communities in synthetic graphs with an accuracy close to the current best alternatives. Additionally, Fluid Communities is the first propagation-based algorithm capable of identifying a variable number of communities in network. To illustrate the relevance of the algorithm, we evaluate the diversity of the communities found by Fluid Communities, and find them to be significantly different from the ones found by alternative methods.Comment: Accepted at the 6th International Conference on Complex Networks and Their Application