Achieving High Speed CFD simulations: Optimization, Parallelization, and FPGA Acceleration for the unstructured DLR TAU Code

Today, large scale parallel simulations are fundamental tools to handle complex problems. The number of processors in current computation platforms has been recently increased and therefore it is necessary to optimize the application performance and to enhance the scalability of massively-parallel systems. In addition, new heterogeneous architectures, combining conventional processors with specific hardware, like FPGAs, to accelerate the most time consuming functions are considered as a strong alternative to boost the performance. In this paper, the performance of the DLR TAU code is analyzed and optimized. The improvement of the code efficiency is addressed through three key activities: Optimization, parallelization and hardware acceleration. At first, a profiling analysis of the most time-consuming processes of the Reynolds Averaged Navier Stokes flow solver on a three-dimensional unstructured mesh is performed. Then, a study of the code scalability with new partitioning algorithms are tested to show the most suitable partitioning algorithms for the selected applications. Finally, a feasibility study on the application of FPGAs and GPUs for the hardware acceleration of CFD simulations is presented

CP violation in B decays: Experimental aspects

This lecture, given at the 2005 European School of High-Energy Physics in Austria in succession of the series on CP Violation by Robert Fleischer, sheds light on the topic from a slightly different perspective, which is meant to be a link between theory and the daily work of experimentalists. An overview of Bmeson experimental history and phenomenology is followed by a description of B-meson production techniques, facilities worldwide, and a list of important present and future experiments. Current analyses are discussed, and their latest results (as of summer of 2005) are given

Efficient polar optimization of transport aircraft in transonic RANS flow using adjoint gradient based approach

A major design requirement for transport aircraft is efficient cruise flight in the transonic region. From the aerodynamic viewpoint, this is achieved by favorable lift-to-drag ratio of the aircraft, both at the main design point and at off-design conditions. We therefore present a method to efficiently perform a multi-point optimization of a representative wing-body configuration. Designs are evaluated with RANS CFD simulations, the wing is parametrized using 40 free-form deformation control points, and a gradient-based method is used to drive the optimization. The gradient of cost functions is computed with a discrete adjoint approach, in which flow and mesh adjoint equations are solved. Compared to single-point optimization, with multi-point optimization we obtain a design with slightly lower best lift-to-drag ratio, but which has improved lift-to-drag polar over the whole range of practical lift coefficients compared to the baseline design

Predictions with Lattice QCD

In recent years, we used lattice QCD to calculate some quantities that were unknown or poorly known. They are the $q^2$ dependence of the form factor in semileptonic $D\to Kl\nu$ decay, the leptonic decay constants of the $D^+$ and $D_s$ mesons, and the mass of the $B_c$ meson. In this paper, we summarize these calculations, with emphasis on their (subsequent) confirmation by measurements in $e^+e^-$, $\gamma p$ and $\bar{p}p$ collisions.Comment: 5 pages; update of hep-lat/0509169, with experimental confirmation of form factors from Belle and fDs from BaBar; presented at SciDAC 2006 for the Fermilab Lattice, MILC, and HPQCD Collaboration

Estimating population density distribution from network-based mobile phone data

In this study we address the problem of leveraging mobile phone network-based data for the task of estimating population density distribution at pan-European level. The primary goal is to develop a methodological framework for the collection and processing of network-based data that can be plausibly applied across multiple MNOs. The proposed method exploits more extensive network topology information than is considered in most state-of-the-art literature, i.e., (approximate) knowledge of cell coverage areas is assumed instead of merely cell tower locations. A distinguishing feature of the proposed methodology is the capability of taking in input a combination of cell-level and Location Area-level data, thus enabling the integration of data from Call Detail Records (CDR) with other network-based data sources, e.g., Visitor Location Register (VLR). Different scenarios are considered in terms of input data availability at individual MNOs (CDR only, VLR only, combinations of CDR and VLR) and for multi-MNO data fusion, and the relevant tradeoff dimensions are discussed. At the core of the proposed method lies a novel formulation of the population distribution estimation as a Maximum Likelihood estimation problem. The proposed estimation method is validated for consistency with synthetically generated data in a simplified simulation scenario.JRC.H.6-Digital Earth and Reference Dat

Beyond backscattering: Optical neuroimaging by BRAD

Optical coherence tomography (OCT) is a powerful technology for rapid volumetric imaging in biomedicine. The bright field imaging approach of conventional OCT systems is based on the detection of directly backscattered light, thereby waiving the wealth of information contained in the angular scattering distribution. Here we demonstrate that the unique features of few-mode fibers (FMF) enable simultaneous bright and dark field (BRAD) imaging for OCT. As backscattered light is picked up by the different modes of a FMF depending upon the angular scattering pattern, we obtain access to the directional scattering signatures of different tissues by decoupling illumination and detection paths. We exploit the distinct modal propagation properties of the FMF in concert with the long coherence lengths provided by modern wavelength-swept lasers to achieve multiplexing of the different modal responses into a combined OCT tomogram. We demonstrate BRAD sensing for distinguishing differently sized microparticles and showcase the performance of BRAD-OCT imaging with enhanced contrast for ex vivo tumorous tissue in glioblastoma and neuritic plaques in Alzheimer's disease

Cool Companions to White Dwarf Stars from the Two Micron All Sky Survey All Sky Data Release

We present the culmination of our near-infrared survey of the optically spectroscopically identified white dwarf stars from the McCook and Sion catalog, conducted using photometric data from the Two Micron All Sky Survey final All Sky Data Release. The color selection technique, which identifies candidate binaries containing a white dwarf and a low-mass stellar (or substellar) companion via their distinctive locus in the near-infrared color-color diagram, is demonstrated to be simple to apply and to yield candidates with a high rate of subsequent confirmation. We recover 105 confirmed binaries, and identify 27 firm candidates (19 of which are new to this work) and 21 tentative candidates (17 of which are new to this work) from the 2MASS data. Only a small number of candidates from our survey have likely companion spectral types later than M5, none of which is an obvious L-type (i.e., potential brown dwarf) companion. Only one previously known white dwarf + brown dwarf binary is detected. This result is discussed in the context of the 2MASS detection limits, as well as other recent observational surveys that suggest a very low rate of formation (or survival) for binary stars with extreme mass ratios

Charm Leptonic and Semileptonic Decays

Experimental results for the pseudoscalar decay constants f_{D} and f_{D_s} are reviewed. Semileptonic form factor results from D -> (pseudoscalar) l nu and D -> (vector) l nu decays are also reviewed.Comment: 8 pages, 4 figures, presented at the 11th International Conference on B-Physics at Hadron Machines (BEAUTY 2006) Sept. 25-29, Oxford, England; corrected typo

Testing QCD Sum Rules on the Light-Cone in D->(pi,K) l nu Decays

We compare the predictions for the form factors f_+^{D->pi,K}(0) from QCD sum rules on the light-cone with recent experimental results. We find f_+^{D->pi}(0) = 0.63\pm 0.11, f_+^{D->K}(0) = 0.75\pm 0.12 and f_+^{D->pi}(0)/f_+^{D->K}(0)= 0.84\pm 0.04 in very good agreement with experiment. Although the uncertainties of the form factors themselves are larger than the current experimental errors and difficult to reduce, their ratio is determined much more accurately and with an accuracy that matches that of experiment.Comment: 12 page