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41.
We study the problem of label ranking, a machine learning task that consists of inducing a mapping from instances to rankings over a finite number of labels. Our learning method, referred to as ranking by pairwise comparison (RPC), first induces pairwise order relations (preferences) from suitable training data, using a natural extension of so-called pairwise classification. A ranking is then derived from a set of such relations by means of a ranking procedure. In this paper, we first elaborate on a key advantage of such a decomposition, namely the fact that it allows the learner to adapt to different loss functions without re-training, by using different ranking procedures on the same predicted order relations. In this regard, we distinguish between two types of errors, called, respectively, ranking error and position error. Focusing on the position error, which has received less attention so far, we then propose a ranking procedure called ranking through iterated choice as well as an efficient pairwise implementation thereof. Apart from a theoretical justification of this procedure, we offer empirical evidence in favor of its superior performance as a risk minimizer for the position error. 相似文献
42.
To understand the handling behaviour of a three-wheeled tilting vehicle, models of the vehicle with different level of detail,
corresponding to specific fields of investigation, have been developed. Then the proposed kinematics of the three-wheeler
are assessed and optimized with respect to desired dynamic properties by applying a detailed multibody system model. The partially
unstable nature of the motion of the vehicle suggests the application of an analytically derived, simplified model, to allow
for focusing on stability aspects and steady-state handling properties. These investigations reveal the necessity of employing
a steer-by-wire control system to support the driver by stabilizing the motion of the vehicle. Thus, an additional basic vehicle
model is derived for control design, and an energy-efficient control strategy is presented. Numerical simulation results demonstrate
the dynamic properties of the optimized kinematics and the control system, approved by successful test runs of a prototype. 相似文献
43.
Antonio de la Oliva Ignacio Soto Albert Banchs Johannes Lessmann Christian Niephaus Telemaco MeliaAuthor vitae 《Computer Standards & Interfaces》2011,33(6):556-564
The IEEE 802.21 standard facilitates media independent handovers by providing higher layer mobility management functions with common service primitives for all technologies. Right after the base specification was published, several voices rose up in the working group advocating to broaden the scope of IEEE 802.21 beyond handovers. This paper aims at updating the reader with the main challenges and functionalities required to create a Media Independence Service Layer, through the analysis of scenarios which are being discussed within the working group: 1) Wireless Coexistence, and 2) Heterogeneous Wireless Multihop Backhaul Networks. 相似文献
44.
Smuc Michael Mayr Eva Lammarsch Tim Aigner Wolfgang Miksch Silvia G rtner Johannes 《Computer Graphics and Applications, IEEE》2009,29(3):29-38
For evaluating visual-analytics tools, many studies confine to scoring user insights into data. For participatory design of those tools, we propose a three-level methodology to make more out of users' insights. The Relational Insight Organizer (RIO) helps to understand how insights emerge and build on one each other. 相似文献
45.
We study four problems from the geometry of numbers, the shortest vector problem (Svp), the closest vector problem (Cvp), the successive minima problem (Smp), and the shortest independent vectors problem (Sivp). Extending and generalizing results of Ajtai, Kumar, and Sivakumar we present probabilistic single exponential time algorithms for all four problems for all ?p norms. The results on Smp and Sivp are new for all norms. The results on Svp and Cvp generalize previous results of Ajtai et al. for the Euclidean ?2 norm to arbitrary ?p norms. We achieve our results by introducing a new lattice problem, the generalized shortest vector problem (GSvp). 1 We describe a single exponential time algorithm for GSvp. We also describe polynomial time reductions from Svp,Cvp,Smp, and Sivp to GSvp, establishing single exponential time algorithms for the four classical lattice problems. This approach leads to a unified algorithmic treatment of the lattice problems Svp,Cvp,Smp, and Sivp. 相似文献
46.
Paul Martinsen Johannes Blaschke Robert Jordan 《Computer Physics Communications》2009,180(10):1983-1989
Modern graphics cards, commonly used in desktop computers, have evolved beyond a simple interface between processor and display to incorporate sophisticated calculation engines that can be applied to general purpose computing. The Monte Carlo algorithm for modelling photon transport in turbid media has been implemented on an NVIDIA® 8800gt graphics card using the CUDA toolkit. The Monte Carlo method relies on following the trajectory of millions of photons through the sample, often taking hours or days to complete. The graphics-processor implementation, processing roughly 110 million scattering events per second, was found to run more than 70 times faster than a similar, single-threaded implementation on a 2.67 GHz desktop computer.
Program summary
Program title: Phoogle-C/Phoogle-GCatalogue identifier: AEEB_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEEB_v1_0.htmlProgram obtainable from: CPC Program Library, Queen's University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 51 264No. of bytes in distributed program, including test data, etc.: 2 238 805Distribution format: tar.gzProgramming language: C++Computer: Designed for Intel PCs. Phoogle-G requires a NVIDIA graphics card with support for CUDA 1.1Operating system: Windows XPHas the code been vectorised or parallelized?: Phoogle-G is written for SIMD architecturesRAM: 1 GBClassification: 21.1External routines: Charles Karney Random number library. Microsoft Foundation Class library. NVIDA CUDA library [1].Nature of problem: The Monte Carlo technique is an effective algorithm for exploring the propagation of light in turbid media. However, accurate results require tracing the path of many photons within the media. The independence of photons naturally lends the Monte Carlo technique to implementation on parallel architectures. Generally, parallel computing can be expensive, but recent advances in consumer grade graphics cards have opened the possibility of high-performance desktop parallel-computing.Solution method: In this pair of programmes we have implemented the Monte Carlo algorithm described by Prahl et al. [2] for photon transport in infinite scattering media to compare the performance of two readily accessible architectures: a standard desktop PC and a consumer grade graphics card from NVIDIA.Restrictions: The graphics card implementation uses single precision floating point numbers for all calculations. Only photon transport from an isotropic point-source is supported. The graphics-card version has no user interface. The simulation parameters must be set in the source code. The desktop version has a simple user interface; however some properties can only be accessed through an ActiveX client (such as Matlab).Additional comments: The random number library used has a LGPL (http://www.gnu.org/copyleft/lesser.html) licence.Running time: Runtime can range from minutes to months depending on the number of photons simulated and the optical properties of the medium.References:- [1]
- http://www.nvidia.com/object/cuda_home.html.
- [2]
- S. Prahl, M. Keijzer, Sl. Jacques, A. Welch, SPIE Institute Series 5 (1989) 102.
47.
Achim Küpper Moritz Diehl Johannes P. Schlöder Hans Georg Bock Sebastian Engell 《Journal of Process Control》2009,19(5):785-802
In this paper, a moving horizon state and parameter estimation scheme for chromatographic simulated moving bed SMB processes is proposed. The simultaneous state and parameter estimation is based on a high-order nonlinear SMB model which incorporates rigorous models of the chromatographic columns and the discrete shiftings of the inlet and outlet ports. The estimation is performed using sparse measurement information: the concentrations of the components are only measured at the two outlet ports (which are periodically switched from one column to the next) and at one fixed location between two columns. The goal is to reconstruct the full state of the system, i.e. the concentration profiles along all columns, and to identify critical model parameters reliably such that the estimated model can be used in the context of online optimizing control. The state estimation scheme is based upon a deterministic model within the prediction horizon, state noise is only present in the state and the parameters prior to and at the beginning of the horizon. By solving the optimization problem with a multiple-shooting method and applying a real-time iteration scheme, the computation times are such that the scheme can be applied online. Numerical simulations of a validated model for a separation problem with nonlinear isotherms of the Langmuir type demonstrate the efficiency of the algorithm. 相似文献
48.
Vinh Phu Nguyen Oriol Lloberas-Valls Martijn Stroeven Lambertus Johannes Sluys 《Computer Methods in Applied Mechanics and Engineering》2011,200(9-12):1220-1236
The existence of a representative volume element (RVE) for a class of quasi-brittle materials having a random heterogeneous microstructure in tensile, shear and mixed mode loading is demonstrated by deriving traction–separation relations, which are objective with respect to RVE size. A computational homogenization based multiscale crack modelling framework, implemented in an FE2 setting, for quasi-brittle solids with complex random microstructure is presented. The objectivity of the macroscopic response to the micro-sample size is shown by numerical simulations. Therefore, a homogenization scheme, which is objective with respect to macroscopic discretization and microscopic sample size, is devised. Numerical examples including a comparison with direct numerical simulation are given to demonstrate the performance of the proposed method. 相似文献
49.
Huth J Buchholz M Kraus JM Mølhave K Gradinaru C v Wichert G Gress TM Neumann H Kestler HA 《Computer methods and programs in biomedicine》2011,104(2):227-234
The direct observation of cells over time using time-lapse microscopy can provide deep insights into many important biological processes. Reliable analyses of motility, proliferation, invasive potential or mortality of cells are essential to many studies involving live cell imaging and can aid in biomarker discovery and diagnostic decisions. Given the vast amount of image- and time-series data produced by modern microscopes, automated analysis is a key feature to capitalize the potential of time-lapse imaging devices. To provide fast and reproducible analyses of multiple aspects of cell behaviour, we developed TimeLapseAnalyzer. Apart from general purpose image enhancements and segmentation procedures, this extensible, self-contained, modular cross-platform package provides dedicated modalities for fast and reliable analysis of multi-target cell tracking, scratch wound healing analysis, cell counting and tube formation analysis in high throughput screening of live-cell experiments. TimeLapseAnalyzer is freely available (MATLAB, Open Source) at http://www.informatik.uni-ulm.de/ni/mitarbeiter/HKestler/tla. 相似文献
50.