Showing papers by "Bauhaus University, Weimar published in 2007"

The influence of calcium content on the structure and thermal performance of fly ash based geopolymers

Abstract: The influence of calcium and its content on the structure formation, hardening, and performance of fly ash based geopolymeric binder was the objective of our investigation. Calcium hydroxide was added to fly ash in different amounts. Since it is known that the formed structure determines certain properties of the material, the coherence between different types and various ratios of the reaction products on thermal properties such as strength after thermal treatment up to 1,100 °C, thermal resistance under load, creep in compression, and axial dilation were investigated. The results were compared to the type and composition of the reaction product, which was detected, for example, by 29Si NMR spectroscopy and X-ray diffraction. Along with calcium containing zeolitic phases, the calcium built C–S–H-phases using the silicon from the fly ash, both of which crystallize or convert into new phases at elevated temperatures.

Consumer File Sharing of Motion Pictures

Abstract: Illegal consumer file sharing of motion pictures is considered a major threat to the movie industry. Whereas industry advocates and some scholars postulate a cannibalistic effect on commercial forms of movie consumption, other researchers deny this effect, though sound evidence is lacking on both sides. Drawing on extant research and utility theory, the authors present hypotheses on the consequences and determinants of consumer file sharing and test them with data from a controlled longitudinal panel study of German consumers. The data contain information on the consumers’ intentions toward and actual behavior in relation to the consumption of 25 new motion pictures, allowing the authors to study more than 10,000 individual file-sharing opportunities. The authors test the effect of file sharing on commercial movie consumption using a series of ReLogit regression analyses and apply partial least squares structural equation modeling to identify the determinants of consumer file sharing. They find evidence of substantial cannibalization of theater visits, DVD rentals, and DVD purchases responsible for annual revenue losses of $300 million in Germany. Five categories of file-sharing behavior drive file sharing and have a significant impact on how consumers obtain and watch illegal movie copies.

Alkali-activated metakaolin-slag blends—performance and structure in dependence of their composition

Abstract: Blast furnace slag and metakaolin were blended together and the combination activated by sodium hydroxide solution. The boundary mixtures were set by the activation of the pure slag and pure metakaolin powders. The type and quantity of the reaction products in the alkaline activated blended binders was determined. It is discussed whether both raw materials react separately and are unaffected by each other or if there is a chemical interaction. The discussion bases on extensive investigations with 29Si and 27Al nuclear magnetic resonance spectroscopy compared with X-ray diffraction and thermal analysis (DTA/TG). Additionally, the strength performance will be presented and related to structure, composition and the amount of the reaction products.

Enabling Mobile Phones To Support Large-Scale Museum Guidance

Abstract: We present a museum guidance system called PhoneGuide that uses widespread camera-equipped mobile phones for on-device object recognition in combination with pervasive tracking. It also provides location- and object-aware multimedia content to museum visitors, and is scalable to cover a large number of museum objects.

The last picture show? Timing and order of movie distribution channels

Abstract: Movies and other media goods are traditionally distributed across distinct sequential channels (e.g., theaters, home video, video on demand). The optimality of the currently employed timing and order of channel openings has become a matter of contentious debate among both industry experts and marketing scholars. In this article, the authors present a model of revenue generation across four sequential distribution channels, combining choice-based conjoint data with other information. Drawing on stratified random samples for three major markets—namely, the United States, Japan, and Germany—and a total of 1770 consumers, the empirical results suggest that the studios that produce motion pictures can increase their revenues by up to 16.2% through sequential distribution chain timing and order changes when applying a common distribution model for all movies in a country and that revenue-optimizing structures differ strongly among countries. Under the conditions of the study, the authors find that the ...

Strategies for retrieving plagiarized documents

Abstract: For the identification of plagiarized passages in large document collections we present retrieval strategies which rely on stochastic sampling and chunk indexes. Using the entire Wikipedia corpus we compile n-gram indexes and compare them to a new kind of fingerprint index in a plagiarism analysis use case. Our index provides an analysis speed-up by factor 1.5 and is an order of magnitude smaller, while being equivalent in terms of precision and recall.

Plagiarism Detection Without Reference Collections

Abstract: Current research in the field of automatic plagiarism detection for text documents focuses on the development of algorithms that compare suspicious documents against potential original documents. Although recent approaches perform well in identifying copied or even modified passages ([Brin et al. (1995), Stein (2005)]), they assume a closed world where a reference collection must be given (Finkel (2002)). Recall that a human reader can identify suspicious passages within a document without having a library of potential original documents in mind.

Determinants of motion picture box office and profitability: an interrelationship approach

Abstract: Introduction Producing and marketing motion pictures is notoriously risky, with only three out of ten movies breaking even and one becoming profitable at the box office. Extending knowledge on the factors that influence a movie’s box-office and on the interrelations between these factors can be seen as major contribution to aid in lowering the number of failures in the motion picture industry. The major aim of this study is to distinguish direct and indirect effects between potential success drivers and motion picture success by understanding the interrelationships among different determinants of movie success.

Principles of hash-based text retrieval

Abstract: Hash-based similarity search reduces a continuous similarity relation to the binary concept "similar or not similar": two feature vectors are considered as similar if they are mapped on the same hash key. From its runtime performance this principle is unequaled--while being unaffected by dimensionality concerns at the same time. Similarity hashing is applied with great success for near similarity search in large document collections, and it is considered as a key technology for near-duplicate detection and plagiarism analysis. This papers reveals the design principles behind hash-based search methods and presents them in a unified way. We introduce new stress statistics that are suited to analyze the performance of hash-based search methods, and we explain the rationale of their effectiveness. Based on these insights, we show how optimum hash functions for similarity search can be derived. We also present new results of a comparative study between different hash-based search methods.

Prakash: lighting aware motion capture using photosensing markers and multiplexed illuminators

Abstract: In this paper, we present a high speed optical motion capture method that can measure three dimensional motion, orientation, and incident illumination at tagged points in a scene. We use tracking tags that work in natural lighting conditions and can be imperceptibly embedded in attire or other objects. Our system supports an unlimited number of tags in a scene, with each tag uniquely identified to eliminate marker reacquisition issues. Our tags also provide incident illumination data which can be used to match scene lighting when inserting synthetic elements. The technique is therefore ideal for on-set motion capture or real-time broadcasting of virtual sets. Unlike previous methods that employ high speed cameras or scanning lasers, we capture the scene appearance using the simplest possible optical devices - a light-emitting diode (LED) with a passive binary mask used as the transmitter and a photosensor used as the receiver. We strategically place a set of optical transmitters to spatio-temporally encode the volume of interest. Photosensors attached to scene points demultiplex the coded optical signals from multiple transmitters, allowing us to compute not only receiver location and orientation but also their incident illumination and the reflectance of the surfaces to which the photosensors are attached. We use our untethered tag system, called Prakash, to demonstrate methods of adding special effects to captured videos that cannot be accomplished using pure vision techniques that rely on camera images.

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.

Dynamic Adaptation of Projected Imperceptible Codes

Abstract: In this paper we present an innovative adaptive imperceptible pattern projection technique that takes into account parameters of human visual perception. A coded image is temporally integrated into the projected image, which is invisible to the human eye but can be reconstructed by a synchronized camera. The embedded code is dynamically adjusted on the fly to guarantee its imperceptibility and to adapt it to the current camera pose. Linked with real-time flash keying, for instance, this enables in-shot optical tracking using a dynamic multi-resolution marker technique. A sample prototype has been realized that demonstrates the application of our method in the context of augmentations in television studios.

Plagiarism analysis, authorship identification, and near-duplicate detection PAN'07

Abstract: Goal of the workshop was to bring together experts and prospective researchers around the exciting and future-oriented topic of plagiarism analysis, authorship identification, and high similarity search. This topic receives increasing attention, which results, among others, from the fact that information about nearly any subject can be found on the World Wide Web.

Post-strengthening of timber structures with CFRP's

Abstract: Upgrading structures for higher working loads or restoring original design strength is an engineering task for structures of any material. A great number of existing buildings need specific interventions on site to restore the damages for renovation, including reinforcement or repair of timber structures due to previous overloading, insect and fungal attack. This article presents a study of reinforcement techniques for restoration and strengthening of existing timber floors under bending loads. Structural adhesives for application on the building site are used and the removal of the overhanging part of the structure as well as the inserted ceiling was not necessary. Commercial adhesives were tested. The tests showed the arrangement of the reinforcement and the stiffness of the materials transmitting the loads, i.e. wood, CFRP and the bonding agent, were of decisive influence for the overall strength of the specimen. The results obtained depend on the wood structure and the presence of defects e.g. knots and cracks. The investigations are currently going on and will be supplemented by using further practice related conditions.

Influence of the clay type on the pore structure of structural ceramics

Abstract: The formation of the microstructures of ceramic bodies during firing depending on the clay type will be presented. Through the separation of four different clay types the microstructural development during firing could be systemised. With regard to the hygric behaviour such as capillary suction and humidity absorption as well as to the durability the clay type depending pore structures will be discussed. The influence of the utilisation of industrial wastes in ceramic bodies on their microstructure will be introduced by first results of a current research project and are exemplified by one clay type.

Surprise, surprise: two distinct components in the visually evoked distractor effect.

Abstract: The distractor effect is an inhibition of saccades shortly after a sudden visual event. It has been explained both as an oculomotor reflex and as a manifestation of the orienting response. To clarify which explanation is more appropriate, we investigated a possible habituation of this effect. Visual and auditory distractors were presented at gaze-contingent intervals during the perception of meaningful pictures. Both reflexlike and modifiable components were present in the visual distractor effect, with latencies of about 110 and 180 ms, respectively. The influence of visual and auditory distractors on saccades preceded the earliest changes in cortical ERPs. Only for long-term habituation in the visual modality was a correlation with ERPs (N1) found.

A Flexible Multi-Volume Shader Framework for Arbitrarily Intersecting Multi-Resolution Datasets

Abstract: We present a powerful framework for 3D-texture-based rendering of multiple arbitrarily intersecting volumetric datasets. Each volume is represented by a multi-resolution octree-based structure and we use out-of-core techniques to support extremely large volumes. Users define a set of convex polyhedral volume lenses, which may be associated with one or more volumetric datasets. The volumes or the lenses can be interactively moved around while the region inside each lens is rendered using interactively defined multi-volume shaders. Our rendering pipeline splits each lens into multiple convex regions such that each region is homogenous and contains a fixed number of volumes. Each such region is further split by the brick boundaries of the associated octree representations. The resulting puzzle of lens fragments is sorted in front-to-back or back-to-front order using a combination of a view-dependent octree traversal and a GPU-based depth peeling technique. Our current implementation uses slice-based volume rendering and allows interactive roaming through multiple intersecting multi-gigabyte volumes.

Proceedings of the 2007 international ACM conference on Supporting group work

Abstract: We are pleased to host Group 2007, a conference that combines world-class research contributions with a beautiful conference location. Group 2007 is part of a series of bi-annual high-impact conferences on computer-based systems that have an impact on groups, organizations, and social networks. For the third time, the conference is being held on beautiful Sanibel Island, on the southwest coast of Florida. Group 2007 will foster a discourse on collaborative technology that bridges the fields of Computer-Supported Cooperative Work (CSCW) and Information Systems (IS). Group 2007 brings together researchers and practitioners from different areas working on the development, introduction, management, deployment, and analysis of computer-based collaborative systems. In these proceedings you will find contributions from academia and industry, including 38 papers (full-length contributions) and 9 notes (papers with smaller yet equally innovative contributions) selected from a record number of submissions (132 papers / 25 notes). This year's program will feature topics including theories of cooperative work and analysis of complex work settings, general questions of interactions in groups for working and learning, awareness and sharing support, technical issues, as well as social computing including social tagging and wikis. Beyond papers and notes, we are excited to host the first ever Doctoral Consortium at Group, sponsored by NSF and Microsoft Research. Thirteen PhD students from five different countries have been selected to participate in a full-day workshop with leading experts in the field. Continuing from previous years, Group 2007 is pleased to also offer workshops, posters, and an opening plenary, not to mention lots of fun in the sun.

How odgcrnwi becomes crowding: stimulus-specific learning reduces crowding.

Abstract: Processes underlying crowding in visual letter recognition were examined by investigating effects of training. Experiment 1 revealed that training reduces crowding mainly for trained strings. This was corroborated in Experiment 2, where no training effects were obvious after 3 days of training when strings changed from trial to trial. Experiment 3 specified that after a short amount of training, learning effects remained specific to trained strings and also to the trained retinal eccentricity and the interletter spacing used in training. Transfer to other than trained conditions was observed only after further training. Experiment 4 showed that transfer occurred earlier when words were used as stimuli. These results thus demonstrate that part of crowding results from the absence of higher level representations of the stimulus. Such representations can be acquired through learning visual properties of the stimulus.

Passive-Active Geometric Calibration for View-Dependent Projections onto Arbitrary Surfaces

Abstract: In this paper we present a hybrid technique for correcting distortions that appear when projecting images onto geometrically complex, colored and textured surfaces. It analyzes the optical flow that results from perspective distortions during motions of the observer and tries to use this information for computing the correct image warping. If this fails due to an unreliable optical flow, an accurate -but slower and visiblestructured light projection is automatically triggered. Together with an appropriate radiometric compensation, view-dependent content can be projected onto arbitrary everyday surfaces. An implementation mainly on the GPU ensures fast frame rates.

Tactile Feedback at the Finger Tips for Improved Direct Interaction in Immersive Environments

Abstract: We present a new tactile feedback system for finger-based interactions in immersive virtual reality applications that consists of shape memory alloy wires wrapped around tracked linger thimbles The wires touch the inside of the finger tips and provide an impression when they are shortened We use this system to communicate linger contacts with virtual objects in an application for usability and reachability studies of car interiors Our experiments and an initial pilot study revealed that this type of feedback helps users to perform direct manipulation tasks with more reliability

Unsynchronized 4D barcodes: coding and decoding time-multiplexed 2D colorcodes

Abstract: We present a novel technique for optical data transfer between public displays and mobile devices based on unsynchronized 4D barcodes. We assume that no direct (electromagnetic or other) connection between the devices can exist. Time-multiplexed, 2D color barcodes are displayed on screens and recorded with camera equipped mobile phones. This allows to transmit information optically between both devices. Our approach maximizes the data throughput and the robustness of the barcode recognition, while no immediate synchronization exists. Although the transfer rate is much smaller than it can be achieved with electromagnetic techniques (e.g., Bluetooth or WiFi), we envision to apply such a technique wherever no direct connection is available. 4D barcodes can, for instance, be integrated into public web-pages, movie sequences, advertisement presentations or information displays, and they encode and transmit more information than possible with single 2D or 3D barcodes.

Shared encounters

Abstract: Our everyday lives are characterised by encounters, some are fleeting and ephemeral and others are more enduring and meaningful exchanges. Shared encounters are the glue of social networks and have a socializing effect in terms of mutual understanding, empathy, respect and thus tolerance towards others. The quality and characteristics of such encounters are affected by the setting, or situation in which they occur. In a world shaped by communication technologies, non-place-based networks often coexist alongside to the traditional local face-to-face social networks. As these multiple and distinct on and off-line communities tend to carry out their activities in more and more distinct and sophisticated spaces, a lack of coherency and fragmentation emerges in the sense of a shared space of community. Open public space with its streets, parks and squares plays an important role in providing space for shared encounters among and between these coexisting networks. Mobile and ubiquitous technologies enable social encounters located in public space, albeit not confined to fixed settings, whilst also offering sharing of experiences from non-place based networks. We will look at how to create or support the conditions for meaningful and persisting shared encounters. In particular we propose to explore how technologies can be appropriated for shared interactions that can occur spontaneously and playfully and in doing so re-inhabit and connect place-based social networks.

Unsynchronized 4D Barcodes

Abstract: We present a novel technique for optical data transfer between public displays and mobile devices based on unsynchronized 4D barcodes. We assume that no direct (electromagnetic or other) connection between the devices can exist. Time-multiplexed, 2D color barcodes are displayed on screens and recorded with camera equipped mobile phones. This allows to transmit information optically between both devices. Our approach maximizes the data throughput and the robustness of the barcode recognition, while no immediate synchronization exists. Although the transfer rate is much smaller than it can be achieved with electromagnetic techniques (e.g., Bluetooth or WiFi), we envision to apply such a technique wherever no direct connection is available. 4D barcodes can, for instance, be integrated into public web-pages, movie sequences, advertisement presentations or information displays, and they encode and transmit more information than possible with single 2D or 3D barcodes.

Modelling of electromagnetic wave propagation along transmission lines in inhomogeneous media

Abstract: Time domain reflectometry (TDR) is a well-established method for the measurement of moisture in various materials, especially soils. Standard waveform analysis usually provides the average water content along the length of the TDR probe, while more sophisticated methods are required to reconstruct the spatial water content profile. A reconstruction algorithm has been developed which uses one- or two-sided reflection data to calculate capacitance and conductivity distributions from which water content profiles can be derived. Several examples demonstrate the performance of the algorithm under various conditions in lossless and lossy materials.

The Tensile Strength of Compacted Clays as Affected by Suction and Soil Structure

Abstract: This paper describes the influence of soil structure and soil suction on the tensile strength of a compacted clay. Laboratory tensile strength tests were carried out on a medium plastic clay. The soil samples were prepared by compacting a soil-water mixture of predetermined water content. The soil samples were either wetted or dried to different water contents corresponding to several suction levels. The test results showed an increase in the tensile strength with higher suction values and that samples compacted at different compaction states reach different magnitudes of tensile strength values.

Nucleation and growth of C-S-H phases on mineral admixtures

Abstract: The reaction of alite with water can be accelerated by adding mineral admixtures such as limestone powder. Two different effects will be discussed in this paper. Firstly, the heterogeneous nucleation of C-S-H phases on surfaces showing a high chemical affinity towards these phases. Secondly, an accelerating effect occurs because of the high specific surface of the admixtures. C-S-H phases can grow on these additional surfaces and thus the dissolution of alite can proceed unhindered leading to a higher degree of hydration for this clinker mineral. Both effects together can be used to improve the performance of blended cements.