Location-based services (LBSs) gain a massive shift in popularity these days and are about to take the next step towards proactive LBSs. In comparison to conventional LBSs, their proactive variant needs continuous pos...
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ISBN:
(纸本)9780769544397
Location-based services (LBSs) gain a massive shift in popularity these days and are about to take the next step towards proactive LBSs. In comparison to conventional LBSs, their proactive variant needs continuous position tracking to monitor spatial objects to detect the relationships between a user and surrounding objects and proactively perform actions. But tracking so far also results in severe battery drain in mobile devices due to deficient positioning APIs and the absence of energy-efficient positioning methods with adequate accuracy. By exploiting the combined information from several positioning technologies with different characteristics in terms of energy consumption, accuracy, precision and availability, this paper proposes a hierarchical positioning algorithm, which provides a general algorithmic optimization in order to extend existing positioning APIs to energy-efficiently track a user's position without diminishing accuracy. The algorithm dynamically deactivates different positioning technologies and only activates the positioning method with the least energy consumption that at the same time provides sufficient accuracy to correctly determine topological relationships. In that way, the algorithm can reliably and accurately determine, if the user leaves or enters predefined geographic areas to trigger events for proactive LBSs while preserving valuable energy resources. First results on Android handsets show a reduction in energy consumption of up to 90 percent in comparison to conventional GPS tracking.
The image distortion model (IDM) is a deformation model that is used for computing the (dis-)similarity between images. Therefore it evaluates displacements of individual pixels between two images within a so-called w...
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The image distortion model (IDM) is a deformation model that is used for computing the (dis-)similarity between images. Therefore it evaluates displacements of individual pixels between two images within a so-called warp range and also takes into account the surrounding pixels (local context). It can be used with a kNN classifier and has shown good retrieval quality in handwritten character recognition as well as in past runs of the medical automatic annotation task of ImageCLEF workshops. However, one of its limitations is computational complexity and the resulting long query response times, that may limit its use for a wider range of applications and for modifications to further improve retrieval quality. In particular an enlarged local context and warp range are candidates for such improvements, but would even further increase computational complexity. In our approach, we therefore apply several optimizations that reduce the retrieval time without degrading the result quality. First, we use an early termination strategy for the individual distance computations which contribute a speedup of a factor of 4.3-4.9. Second, we make efficient use of multithreading. With these extensions, we are able to perform the IDM in less than 1.5 s per query on an 8-way server and 16 s on a standard Pentium 4 PC without any degradation of retrieval quality compared to the non-optimized version. We extend the possible displacements to an area of 7 x 7 pixels, using a local context of either 5 x 5 or 7 x 7 pixels. The results of the extended IDM have been submitted to the medical automatic annotation task of ImageCLEF 2007 and were ranked in the upper third. More importantly, the used techniques for reducing the execution time are not limited strictly to IDM but are also applicable to other expensive distance measures. (C) 2008 Elsevier B.V. All rights reserved.
A collection of techniques is developed in this paper for ray casting free-form deformed-volume objects with high quality and efficiency. The known inverse ray deformation approach is combined with free-form deformati...
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A collection of techniques is developed in this paper for ray casting free-form deformed-volume objects with high quality and efficiency. The known inverse ray deformation approach is combined with free-form deformation to bend the rays to the opposite direction of the deformation, producing an image of the deformed volume without generating a really deformed intermediate volume. The local curvature is estimated and used for the adaptive selection of the length of polyline segments, which approximate the inversely deformed ray trajectories;thus longer polyline segments can be automatically selected in regions with small curvature, reducing deformation calculation without losing the spatial continuity of the simulated deformation. We developed an efficient method for the estimation of the local deformation function. The Jacobian of the local deformation function is used for adjustments of the opacity values and normal vectors computed from the original volume, guaranteeing that the deformed spatial structures are correctly rendered. The popular ray casting acceleration techniques, like early ray termination and space leaping, are incorporated into the deformation procedure, providing a speed-up factor of 2.34-6.56 compared to the nonoptimized case. Copyright (C) 2003 John Wiley Sons, Ltd.
GROMACS 3.0 is the latest release of a versatile and very well optimized package for molecular simulation. Much effort has been devoted to achieving extremely high performance on both workstations and parallel compute...
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GROMACS 3.0 is the latest release of a versatile and very well optimized package for molecular simulation. Much effort has been devoted to achieving extremely high performance on both workstations and parallel computers. The design includes an extraction of virial and periodic boundary conditions from the loops over pairwise interactions, and special software routines to enable rapid calculation of x(-1/2). Inner loops are generated automatically in C or Fortran at compile time, with optimizations adapted to each architecture. Assembly loops using SSE and 3DNow! Multimedia instructions are provided for x86 processors, resulting in exceptional performance on inexpensive PC workstations. The interface is simple and easy to use (no scripting language), based on standard command line arguments with self-explanatory functionality and integrated documentation. All binary files are independent of hardware endian and can be read by versions of GROMACS compiled using different floating-point precision. A large collection of flexible tools for trajectory analysis is included, with output in the form of finished Xmgr/Grace graphs. A basic trajectory viewer is included, and several external visualization tools can read the GROMACS trajectory format. Starting with version 3.0, GROMACS is available under the GNU General Public License from http://***.
We present a novel approach for post-mapping optimization. We exploit the concept of generalised matching, a technique that finds symbolically all possible matching assignments of library cells to a multi-output netwo...
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ISBN:
(纸本)9780818682001
We present a novel approach for post-mapping optimization. We exploit the concept of generalised matching, a technique that finds symbolically all possible matching assignments of library cells to a multi-output network specified by a Boolean relation. Several objectives are targeted: area minimization under delay constraints; power minimization under delay constraints; and unconstrained delay minimization. We describe the theory of generalized matching and the algorithmic optimization required for its efficient and robust implementation. A tool based on generalized matching has been implemented and tested on large examples of the MCNC'91 benchmark suite. We obtain sizable improvements in: speed (6% in average, up to 20.7%); area under speed constraints (13.7% an average, up to 29.5%); and power under speed constraints (22.3% in average, up to 38.1%).
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