Showing papers by "Bauhaus University, Weimar published in 2008"

A Wikipedia-based multilingual retrieval model

Abstract: This paper introduces CL-ESA, a new multilingual retrieval model for the analysis of cross-language similarity. The retrieval model exploits the multilingual alignment of Wikipedia: given a document d written in language L we construct a concept vector d for d, where each dimension i in d quantifies the similarity of d with respect to a document di* chosen from the "L-subset" of Wikipedia. Likewise, for a second document d′ written in language L′, L ≠ L′, we construct a concept vector d′, using from the L′-subset of the Wikipedia the topic-aligned counterparts d′i* of our previously chosen documents.Since the two concept vectors d and d′ are collection-relative representations of d and d′ they are language-independent. I. e., their similarity can directly be computed with the cosine similarity measure, for instance.We present results of an extensive analysis that demonstrates the power of this new retrieval model: for a query document d the topically most similar documents from a corpus in another language are properly ranked. Salient property of the new retrieval model is its robustness with respect to both the size and the quality of the index document collection.

Automatic vandalism detection in Wikipedia

Abstract: We present results of a new approach to detect destructive article revisions, so-called vandalism, inWikipedia. Vandalism detection is a one-class classification problem, where vandalism edits are the target to be identified among all revisions. Interestingly, vandalism detection has not been addressed in the Information Retrieval literature by now. In this paper we discuss the characteristics of vandalism as humans recognize it and develop features to render vandalism detection as a machine learning task. We compiled a large number of vandalism edits in a corpus, which allows for the comparison of existing and new detection approaches. Using logistic regression we achieve 83% precision at 77% recall with our model. Compared to the rule-based methods that are currently applied in Wikipedia, our approach increases the F-Measure performance by 49% while being faster at the same time.

3D User Interfaces: New Directions and Perspectives

Abstract: Three-dimensional user interfaces (3D UIs) let users interact with virtual objects, environments, or information using direct 3D input in the physical and/or virtual space. In this article, the founders and organizers of the IEEE Symposium on 3D User Interfaces reflect on the state of the art in several key aspects of 3D UIs and speculate on future research.

The visual computing of projector-camera systems

Abstract: This article focuses on real-time image correction techniques that enable projector-camera systems to display images onto screens that are not optimized for projections, such as geometrically complex, colored and textured surfaces. It reviews hardware accelerated methods like pixel-precise geometric warping, radiometric compensation, multi-focal projection, and the correction of general light modulation effects. Online and offline calibration as well as invisible coding methods are explained. Novel attempts in super-resolution, high dynamic range and high-speed projection are discussed. These techniques open a variety of new applications for projection displays. Some of them will also be presented in this report.

Mendeley - A Last.fm For Research?

Abstract: This paper aims to explore how the principles of a well-known Web 2.0 service, the world?s largest social music service "Last.fm" (www.last.fm), can be applied to research, which potential it could have in the world of research (e.g. an open and interdisciplinary database, usage-based reputation metrics, and collaborative filtering) and which challenges such a model would face in academia. A real-world application of these principles, "Mendeley" (www.mendeley.com), will be demoed at the IEEE e-Science Conference 2008.

A method for predicting swelling pressure of compacted bentonites

Abstract: An approach for predicting swelling pressure of bentonites based on thermodynamic relationships between swelling pressure and suction is presented in this paper. The proposed method requires sorption isotherm data of the bentonites. A series of swelling pressure tests were performed on compacted specimens of bentonite-sand mixtures with different bentonite contents, water contents, and dry densities. The sorption isotherm of the pure bentonite was measured using a chilled-mirror hygrometer. It is found that the method works well for the bentonite-sand mixtures tested. Several published data on bentonites that have been proposed to be used as buffer and sealing material for nuclear waste repository were collected and used to verify the method. The proposed method is found to be also applicable for other bentonites of different types and therefore, can be used to predict swelling pressure of bentonites.

Real-Time Adaptive Radiometric Compensation

Abstract: Recent radiometric compensation techniques make it possible to project images onto colored and textured surfaces. This is realized with projector-camera systems by scanning the projection surface on a per-pixel basis. Using the captured information, a compensation image is calculated that neutralizes geometric distortions and color blending caused by the underlying surface. As a result, the brightness and the contrast of the input image is reduced compared to a conventional projection onto a white canvas. If the input image is not manipulated in its intensities, the compensation image can contain values that are outside the dynamic range of the projector. These will lead to clipping errors and to visible artifacts on the surface. In this article, we present an innovative algorithm that dynamically adjusts the content of the input images before radiometric compensation is carried out. This reduces the perceived visual artifacts while simultaneously preserving a maximum of luminance and contrast. The algorithm is implemented entirely on the GPU and is the first of its kind to run in real time.

Gazing with pEYEs: towards a universal input for various applications

Abstract: Various interfaces for gaze control (which are recommended due to certain requirements of controlling a machine by gaze) have already been developed. One problem, especially for novice users, is that respective interfaces all look different and require different steps to use. As a means to unify interfaces for gaze control, pie menus are suggested. Such pEYEs allow for universal input in various applications usable by novices and by experts. We present two examples for pEYE interfaces; one eye-typing application and one desktop navigation. Observations in user studies indicate effective and efficient performance and a large acceptance.

Low‐Temperature Aging Behavior of Alumina‐Toughened Zirconia

Abstract: The corrosion of alumina-toughened zirconia (ATZ) as a consequence of hydrothermal treatment was investigated, especially the transformation kinetics from tetragonal zirconia to the monoclinic phase. For this purpose, polished ATZ specimens (R a <5 nm) were aged in water vapor at different temperatures ranging from 70° to 134°C. The fraction of the monoclinic phase was determined using X-ray diffraction and Rietveld refinement. The isothermal transformation curves obtained were fitted to the Mehl-Johnson-Avrami equation by least squares. An Arrhenius plot of the fitted transformation rates was used to determine the activation energy and the pre-exponential factor. Following this procedure, the kinetic parameters of the phase transformation were extrapolated down to body temperature and the formation of the monoclinic phase was simulated. In addition, optical interferometry on well-polished specimens (R a < 2 nm) was alternatively used to calculate the monoclinic fraction from the histogram dataset. The results agree very well with those of the X-ray measurements. Additionally, the development of surface roughness with increasing aging time is discussed.

User Interface Design Principles for Interactive Television Applications

Abstract: Interactive Television (ITV) applications gratify entertainment needs and leisure activities in a relaxed domestic context Then, the mentality of efficiency and task completion implied by many user interface heuristics may not be suitable for design and expert evaluation of ITV In line with the contemporary movement towards the design of the user experience of computing systems, a set of design principles for ITV applications has been developed Instead of information technology, the field of communication science was explored, which has accumulated an extensive theory of TV usage and viewer behavior For the empirical validation, the principles were employed in the design of an interactive music TV application The results suggest that a small set of generic principles could support the systematic design of ITV applications and produce a design rationale that is traceable and comparable to alternative solutions, during the process of early product development In addition, the principles could be refin

Mobile Augmented Reality in industrial applications: Approaches for solution of user-related issues

Abstract: Augmented Reality (AR) uses computer-generated virtual information to enhance the userpsilas information access While numerous previous studies have demonstrated the large potential of AR to improve industrial processes by enhancing product quality and reducing production times it is still unclear if and how long term usage of such AR technology produces stress and strain This paper presents an approach to use the analysis of Heart Rate Variability to objectively measure current user strain during different work tasks Results of a user study comparing strain during an AR supported and a non-AR supported work task in a laboratory setting are presented and discussed

Ultrasonic Imaging Methods for Investigation of Post-tensioned Concrete Structures: A Study of Interfaces at Artificial Grouting Faults and Its Verification

Abstract: This paper presents the progress of successful location of grouting faults in tendon ducts with ultrasonic imaging. The examples were obtained in the research group FOR 384 funded by DFG (German Research Foundation). The co-operation of experimental research and modeling allowed imaging and identification of grouted and ungrouted areas of tendon ducts (including strands) in a large test specimen (40 m2). In addition to the criteria for indicating grouting faults in post-tensioned ducts known until now the phase evaluation of reflected ultrasonic pulses is described. Experiments and modeling of wave propagation are presented for reflections at metal plates in concrete (thickness range 0.5 mm to 40 mm) and for tendon ducts including strands. The main part of the progress was achieved by automated measurements using dry contact transducers, 3D-SAFT reconstruction including phase evaluation and modeling considering wave propagation for typical elastic parameters and exact experimental site conditions. The results for shear waves as well as for pressure waves are compared in the frequency range from 50 kHz to 120 kHz.

Superimposing dynamic range

Abstract: We present a simple and cost-efficient way of extending contrast, perceived tonal resolution, and color space of reflective media, such as paper prints, hardcopy photographs, or electronic paper displays. A calibrated projector-camera system is applied for automatic registration, radiometric scanning and superimposition. A second modulation of the projected light on the surface of such media results in a high dynamic range visualization. This holds application potential for a variety of domains, such as radiology, astronomy, optical microscopy, conservation and restoration of historic art, modern art and entertainment installations.

Inverse parameter identification technique using PSO algorithm applied to geotechnical modeling

Abstract: This paper presents a concept for the application of particle swarm optimization in geotechnical engineering. For the calculation of deformations in soil or rock, numerical simulations based on continuum methods are widely used. The material behavior is modeled using constitutive relations that require sets of material parameters to be specified. We present an inverse parameter identification technique, based on statistical analyses and a particle swarm optimization algorithm, to be used in the calibration process of geomechanical models. Its application is demonstrated with typical examples from the fields of soil mechanics and engineering geology. The results for two different laboratory tests and a natural slope clearly show that particle swarms are an efficient and fast tool for finding improved parameter sets to represent the measured reference data.

New concepts for moving least squares: An interpolating non-singular weighting function and weighted nodal least squares

Abstract: In this paper two new concepts for the classical moving least squares (MLS) approach are presented. The first one is an interpolating weighting function, which leads to MLS shape functions fulfilling the interpolation condition exactly. This enables a direct application of essential boundary conditions in the element-free Galerkin method without additional numerical effort. In contrast to existing approaches using singular weighting functions, this new weighting type leads to regular values of the weights and coefficients matrices in the whole domain even at the support points. The second enhancement is an approach, where the computation of the polynomial coefficient matrices is performed only at the nodes. At the interpolation point then a simple operation leads to the final shape function values. The basis polynomial of each node can be chosen independently which enables the simple realization of a p-adaptive scheme.

Humidity controlled calorimetric investigation of the hydration of MgSO4 hydrates

Abstract: The isothermal heat of hydration of MgSO4 hydrates was studied by humidity controlled calorimetry. Two hydrates, starkeyite (MgSO4·4H2O) and a mixture of MgSO4 hydrates with summary 1.3 mol H2O were investigated. The solid-gas reactions were initiated at 30°C and 85% relative humidity. The heat of hydration was determined in a circulation cell in the calorimeter C80 (Setaram). The crystal phases formed after the hydration process were analyzed by thermogravimetry (TG) and X-ray powder diffraction (XRD). Starkeyite reacted with the water vapour to the thermodynamic stable epsomite and the MgSO4 hydrate mixture with 1.3 mol water to hexahydrite. The hydration heats of starkeyite and the mixture were determined to be −169±3 and −257±5 kJmol−1, respectively.

Mobile Phone-Enabled Museum Guidance with Adaptive Classification

Abstract: We present an overview of our adaptive museum guidance system called PhoneGuide. It uses camera-equipped mobile phones for on-device object recognition in ad-hoc sensor networks and provides location and object aware multimedia content to museum visitors.

Retrieval Models for Genre Classification

Abstract: Genre provides a characterization of a document with respect to its form or functional trait. Genre is orthogonal to topic, rendering genre information a powerful filter technology for information seekers in digital li- braries. However, an efficient means for genre classification is an open and controversially discussed issue. This paper gives an overview and presents new results related to automatic genre classification of text documents. We present a comprehensive survey which contrasts the genre retrieval models that have been developed for Web and non-Web corpora. With the concept of genre-specific core vocabularies the paper provides an original contribu - tion related to computational aspects and classification performance of genre retrieval models: we show how such vocabularies are acquired automatical- ly and introduce new concentration measures that quantify the vocabulary distribution in a sensible way. Based on these findings we construct light- weight genre retrieval models and evaluate their discriminative power and computational efficiency. The presented concepts go beyond the existing utilization of vocabulary-centered, genre-revealing features and open new possibilities for the construction of genre classifiers that operate in real-time.

On object selection in gaze controlled environments

Abstract: In the past twenty years, gaze control has become a reliable alternative input method not only for handicapped users. The selection of objects, however, which is of highest importance and of highest frequency in computer control, requires explicit control not inherent in eye movements. Objects have been therefore usually selected via prolonged fixations (dwell times). Dwell times seemed to be for many years the unique reliable method for selection. In this paper, we review pros and cons of classical selection methods and novel metaphors, which are based on pies and gestures. The focus is on the effectiveness and efficiency of selections. In order to estimate the potential of current suggestions for selection, a basic empirical comparison is recommended.

Comparative Performance Tests and Validation of NDT Methods for Concrete Testing

Abstract: Validation of non-destructive testing methods is necessary to create a common basis where different systems can be compared and their applications and limitations be identified. This can be achieved through comparing the measurements taken by several systems used for a common diagnostic purpose under practical but controlled testing conditions. Well-designed small and large laboratory or field specimens promise such conditions. The special concrete specimen (LCS) at BAM was constructed for validation purposes, in particular, to be used for evaluating the performance of echo methods. The thickness of the specimen is varying and it contains carefully designed built-in faults, such as voids, honeycombs and tendon ducts with various degrees of grouting defects. Since the geometry and condition of the defects are known, it can be used to compare the performance of radar, ultrasonic, impact-echo. The research was conducted within the Research group FOR384, sponsored by the German Research Society DFG.

Adaptive Damage Simulation of Concrete Using Heterogeneous Multiscale Models

Abstract: In this paper, an adaptive heterogeneous multiscale model, which couples substructures with different length scales into one numerical model, is introduced for the simulation of damage in concrete. In the presented approach, the evolution of microcracks is simulated using a mesoscale model, which explicitly represents the heterogeneous material structure of concrete, namely aggregates, mortar matrix and interfacial transition zone. The mesoscale model is restricted to the damaged parts of the structure, whereas undamaged regions are simulated on the macroscale. As a result, an adaptive enlargement of the mesoscale model during the simulation is necessary.In the first part of the paper, the generation of the heterogeneous mesoscopic structure of concrete, the finite element discretization of the mesoscale model, the applied isotropic damage model and the cohesive zone model are briefly introduced. Furthermore, the mesoscale simulation of a uniaxial tension test of a concrete prism is presented and own obta...

Slide Attacks on a Class of Hash Functions

Abstract: This paper studies the application of slide attacks to hash functions. Slide attacks have mostly been used for block cipher cryptanalysis. But, as shown in the current paper, they also form a potential threat for hash functions, namely for sponge-function like structures. As it turns out, certain constructions for hash-function-based MACs can be vulnerable to forgery and even to key recovery attacks. In other cases, we can at least distinguish a given hash function from a random oracle. To illustrate our results, we describe attacks against the Grindahl -256 and Grindahl -512 hash functions. To the best of our knowledge, this is the first cryptanalytic result on Grindahl -512. Furthermore, we point out a slide-based distinguisher attack on a slightly modified version of RadioGatun . We finally discuss simple countermeasures as a defense against slide attacks.