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211.
Juha K. Laurila Daniel Gatica-Perez Imad Aad Jan Blom Olivier Bornet Trinh Minh Tri Do Olivier Dousse Julien Eberle Markus Miettinen 《Pervasive and Mobile Computing》2013,9(6):752-771
This paper presents an overview of the Mobile Data Challenge (MDC), a large-scale research initiative aimed at generating innovations around smartphone-based research, as well as community-based evaluation of mobile data analysis methodologies. First, we review the Lausanne Data Collection Campaign (LDCC), an initiative to collect unique longitudinal smartphone dataset for the MDC. Then, we introduce the Open and Dedicated Tracks of the MDC, describe the specific datasets used in each of them, discuss the key design and implementation aspects introduced in order to generate privacy-preserving and scientifically relevant mobile data resources for wider use by the research community, and summarize the main research trends found among the 100+ challenge submissions. We finalize by discussing the main lessons learned from the participation of several hundred researchers worldwide in the MDC Tracks. 相似文献
212.
Gorka Epelde Eduardo Carrasco Gottfried Zimmermann Jan Alexandersson Robert Neßelrath Markus Dubielzig 《Universal Access in the Information Society》2013,12(1):73-87
This paper presents a new approach to make current and future television universally accessible. The proposed approach provides a means of universal accessibility both for remotely operating the TV set and for interacting with online services delivered through the TV. This proposal is based on the ISO/IEC 24752 “Universal Remote Console” (URC) standard. This standard defines an abstract user interface layer called the “user interface socket” and allows the development of pluggable (plug-in) user interfaces for any type of user and any control device. The proposed approach lays the foundation for the development of advanced user interfaces that can be interacted within various modalities. Different prototypes have been developed based on this approach and tested with end users. The user tests have shown this approach to be a viable option for the proposed scenarios. Based on the experience gathered with the prototypes, recommendations and implementation options are suggested for commercial adoption. 相似文献
213.
Michael Herbst Swen Gottschalk Martin Reißel Horst Hardelauf Roy Kasteel Matthieu Javaux Jan Vanderborght Harry Vereecken 《Computers & Geosciences》2008,34(12):1958-1963
In this paper, we present a class of preconditioning methods for a parallel solution of the three-dimensional Richards equation. The preconditioning methods Jacobi scaling, block-Jacobi, incomplete lower–upper, incomplete Cholesky and algebraic multigrid were applied in combination with a parallel conjugate gradient solver and tested for robustness and convergence using two model scenarios. The first scenario was an infiltration into initially dry, sandy soil discretised in 500,000 nodes. The second scenario comprised spatially distributed soil properties using 275,706 numerical nodes and atmospheric boundary conditions. Computational results showed a high efficiency of the nonlinear parallel solution procedure for both scenarios using up to 64 processors. Using 32 processors for the first scenario reduced the wall clock time to slightly more than 1% of the single processor run. For scenario 2 the use of 64 processors reduces the wall clock time to slightly more than 20% of the 8 processors wall clock time. The difference in the efficiency of the various preconditioning methods is moderate but not negligible. The use of the multigrid preconditioning algorithm is recommended, since on average it performed best for both scenarios. 相似文献
214.
In this paper we present a new practical camera characterization technique to improve color accuracy in high dynamic range (HDR) imaging. Camera characterization refers to the process of mapping device‐dependent signals, such as digital camera RAW images, into a well‐defined color space. This is a well‐understood process for low dynamic range (LDR) imaging and is part of most digital cameras — usually mapping from the raw camera signal to the sRGB or Adobe RGB color space. This paper presents an efficient and accurate characterization method for high dynamic range imaging that extends previous methods originally designed for LDR imaging. We demonstrate that our characterization method is very accurate even in unknown illumination conditions, effectively turning a digital camera into a measurement device that measures physically accurate radiance values — both in terms of luminance and color — rivaling more expensive measurement instruments. 相似文献
215.
Operations research and management science are often confronted with sequential decision making problems with large state spaces. Standard methods that are used for solving such complex problems are associated with some difficulties. As we discuss in this article, these methods are plagued by the so-called curse of dimensionality and the curse of modelling. In this article, we discuss reinforcement learning, a machine learning technique for solving sequential decision making problems with large state spaces. We describe how reinforcement learning can be combined with a function approximation method to avoid both the curse of dimensionality and the curse of modelling. To illustrate the usefulness of this approach, we apply it to a problem with a huge state space—learning to play the game of Othello. We describe experiments in which reinforcement learning agents learn to play the game of Othello without the use of any knowledge provided by human experts. It turns out that the reinforcement learning agents learn to play the game of Othello better than players that use basic strategies. 相似文献
216.
Various machine learning problems rely on kernel-based methods. The power of these methods resides in the ability to solve highly nonlinear problems by reformulating them in a linear context. The dominant eigenspace of a (normalized) kernel matrix is often required. Unfortunately, the computational requirements of the existing kernel methods are such that the applicability is restricted to relatively small data sets. This letter therefore focuses on a kernel-based method for large data sets. More specifically, a numerically stable tracking algorithm for the dominant eigenspace of a normalized kernel matrix is proposed, which proceeds by an updating (the addition of a new data point) followed by a downdating (the exclusion of an old data point) of the kernel matrix. Testing the algorithm on some representative case studies reveals that a very good approximation of the dominant eigenspace is obtained, while only a minimal amount of operations and memory space per iteration step is required. 相似文献
217.
Jan Rosell Carlos Vázquez Alexander Pérez Pedro Iñiguez 《Journal of Intelligent and Robotic Systems》2008,53(3):223-245
Haptic devices allow a user to feel either reaction forces from virtual interactions or reaction forces reflected from a remote
site during a bilateral teleoperation task. Also, guiding forces can be exerted to train the user in the performance of a
virtual task or to assist him/her to safely teleoperate a robot. The generation of guiding forces relies on the existence
of a motion plan that provides the direction to be followed to reach the goal from any free configuration of the configuration
space (-space). This paper proposes a method to obtain such a plan that interleaves a sampling-based exploration of -space with an efficient computation of harmonic functions. A deterministic sampling sequence (with a bias based on harmonic
function values) is used to obtain a hierarchical cell decomposition model of -space. A harmonic function is iteratively computed over the partially known model using a novel approach. The harmonic function
is the navigation function used as motion plan. The approach has been implemented in a planner (called the Kautham planner) that, given an initial and a goal configuration, provides: (a) a channel of cells connecting the cell that contains
the initial configuration with the cell that contains the goal configuration; (b) two harmonic functions over the whole -space, one that guides motions towards the channel and another that guides motions within the channel towards the goal; and
(c) a path computed over a roadmap built with the free samples of the channel. The harmonic functions and the solution path
are then used to generate the guiding forces for the haptic device. The planning approach is illustrated with examples on
2D and 3D workspaces.
This work was partially supported by the CICYT projects DPI2005-00112 and DPI2007-63665. 相似文献
218.
Marcelo Siqueira Longin Jan Latecki Nicholas Tustison Jean Gallier James Gee 《Journal of Mathematical Imaging and Vision》2008,30(3):249-274
We present here a new randomized algorithm for repairing the topology of objects represented by 3D binary digital images.
By “repairing the topology”, we mean a systematic way of modifying a given binary image in order to produce a similar binary
image which is guaranteed to be well-composed. A 3D binary digital image is said to be well-composed if, and only if, the square faces shared by background and foreground
voxels form a 2D manifold. Well-composed images enjoy some special properties which can make such images very desirable in
practical applications. For instance, well-known algorithms for extracting surfaces from and thinning binary images can be
simplified and optimized for speed if the input image is assumed to be well-composed. Furthermore, some algorithms for computing
surface curvature and extracting adaptive triangulated surfaces, directly from the binary data, can only be applied to well-composed
images. Finally, we introduce an extension of the aforementioned algorithm to repairing 3D digital multivalued images. Such
an algorithm finds application in repairing segmented images resulting from multi-object segmentations of other 3D digital
multivalued images.
相似文献
James GeeEmail: |
219.
The “visual space” of an optical observer situated at a single, fixed viewpoint is necessarily very ambiguous. Although the structure of the “visual field” (the lateral dimensions, i.e., the “image”) is well defined, the “depth” dimension has to be inferred from the image on the basis of “monocular depth cues” such as occlusion, shading, etc. Such cues are in no way “given”, but are guesses on the basis of prior knowledge about the generic structure of the world and the laws of optics. Thus such a guess is like a hallucination that is used to tentatively interpret image structures as depth cues. The guesses are successful if they lead to a coherent interpretation. Such “controlled hallucination” (in psychological terminology) is similar to the “analysis by synthesis” of computer vision. Although highly ambiguous, visual spaces do have geometrical structure. The group of ambiguities left open by the cues (e.g., the well known bas-relief ambiguity in the case of shape from shading) may be interpreted as the group of congruences (proper motions) of the space. The general structure of visual spaces for different visual fields is explored in the paper. Applications include improved viewing systems for optical man-machine interfaces. 相似文献
220.
Dr. Jan U. Becker Prof. Dr. Michel Clement Dipl.-Kffr. Ute Schaedel 《WIRTSCHAFTSINFORMATIK》2008,50(6):482-488
Shared WiFi-Communities emerge when users share their private Wireless Fidelity with others and in return get free internet access via community members’ internet connection. Supply of wireless capacity and demand for WLAN usually are coordinated by a central authority therewith users can find specific hosts within the community. Initial players that conduct commercial WiFi-Communities established their position in the market. The international market leader with 170,000 hotspots worldwide is FON. The commercial success of shared WiFi-communities (e.g. FON) depends on the adoption of a special router or modifications of the existing WLAN-infrastructure. More importantly it is essential that users permanently offer broadband capacity to the community. Only then net effects can durably generate enhanced usage benefits. A survey of 268 German FON users reveals that the community shows a high level of cohesion. Users barely vary from the default setting concerning shared bandwidth of the router. Additionally most interviewees offer their WLAN 24 hours a day. Despite the possibility of earning money with the wireless capacity most users do not offer bandwidth with a purely economic ambition. Although the market potential of shared WiFi communities appears tremendous legal obstructions and technical restraints exacerbate penetration. 相似文献