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Graz, Austria

The Graz University of Technology is the second largest university in Styria, Austria, after the University of Graz. Austria has three universities of technology – in Graz, in Leoben, and in Vienna. The Graz University of Technology was founded in 1811 by Archduke John of Austria. TU Graz is a public university. In the academic year 2013/14, 15.9% of the students were from abroad and 22.6% of the students were female out of the 12,565 students enrolled at the TU Graz. Wikipedia.


Delgado Y.,University of Graz | Evertz H.G.,Graz University of Technology | Gattringer C.,University of Graz
Acta Physica Polonica B, Proceedings Supplement | Year: 2011

We discuss an effective theory for QCD at finite chemical potential and non-zero temperature, where QCD is reduced to its center degrees of freedom. The effective action can be mapped to a flux representation, where the complex phase problem is solved and the theory accessible to Monte Carlo techniques. In this work, we use a generalized Prokof'ev-Svistunov worm algorithm to perform the simulations and determine the phase diagram as a function of temperature, quark mass and chemical potential. It turns out that the transition is qualitatively as expected for QCD.


Sitthisak O.,Thaksin University | Gilbert L.,University of Southampton | Albert D.,Graz University of Technology | Albert D.,University of Graz
Proceedings - 2nd IIAI International Conference on Advanced Applied Informatics, IIAI-AAI 2013 | Year: 2013

A model for the interactions in an assessment to support learning identifies the need for response options and for contingent feedback, both of which pose problems when computer-aided. Apart from the difficulties of allowing arbitrary student responses, of judging them for correctness or error, and of providing appropriate specific and contingent feedback, explicitly identifying a range of options or alternatives from which a student may make selections remains an unsolved research problem. The 'Knowledge Space Theory (KST)' model of the domain 'problems' provides some opportunity for response options. The 'Competence Based Assessment (COMBA)' model of the required knowledge provides some opportunity for relevant feedback. The paper explores ComKoS, a model which integrates both approaches. We propose to apply ComKoS and IMS QTI in Moodle to instantiate the design and development of one kind of adaptive testing system. This implementation overcomes limitations in adaptability, interoperability, portability, and reusability. Key benefits of this implementation are identified and possibilities suggestion for future work is provided. © 2013 IEEE.


Varghese S.,IMDEA Madrid Institute for Advanced Studies | Yoon S.-J.,Seoul National University | Casado S.,IMDEA Madrid Institute for Advanced Studies | Fischer R.C.,Graz University of Technology | And 3 more authors.
Advanced Optical Materials | Year: 2014

Stimulated emission in highly luminescent molecular crystals of a dicyanodistyrylbenzene derivative with orthogonal resonator modes, very low lasing threshold, an excellent quality factor, and high mode regularity is demonstrated. The orthogonal resonator mode-endorsed single crystals acts as 3D resonator cavities and can be effectively implemented as the active medium in organic solid-state lasers without any external resonator structures. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Daemen J.,STMicroelectronics | Rijmen V.,Graz University of Technology
Cryptology and Information Security Series | Year: 2011

In this paper we provide a description of Rijndael using only algebraic operations in GF(2 8). How the elements of GF(2 8) are represented in bytes can be seen as a detail of the specification. In classical correlation analysis such as linear cryptanalysis, however, one works at the bit level and must assume a specific representation to study the propagation properties. We demonstrate how to conduct correlation analysis at the level of elements of GF(2 n), without having to deal with representation issues. While this approach does not result in better bounds or stronger attacks, it allows to analytically address the resistance against linear cryptanalysis similar to what has been done for differential cryptanalysis in [3]. Further we show how linear functions over GF(2) n map one-to-one to linear functions over GF(2 n) by the choice of a basis, and make the link with their mask propagation properties. © 2011 The authors and IOS Press. All rights reserved.


Buchgraber T.,Graz University of Technology | Shutin D.,Princeton University | Poor H.V.,Princeton University
ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings | Year: 2011

In this work a new online learning algorithm that uses automatic relevance determination (ARD) is proposed for fast adaptive nonlinear filtering. A sequential decision rule for inclusion or deletion of basis functions is obtained by applying a recently proposed fast variational sparse Bayesian learning (SBL) method. The proposed scheme uses a sliding window estimator to process the data in an online fashion. The noise variance can be implicitly estimated by the algorithm. It is shown that the described method has better mean square error (MSE) performance than a state of the art kernel recursive least squares (Kernel-RLS) algorithm when using the same number of basis functions. © 2011 IEEE.


Hafele V.,University of Graz | De Leon-Perez F.,University of Zaragoza | De Leon-Perez F.,Centro Universitario Of La Defensa Of Zaragoza | Hohenau A.,University of Graz | And 4 more authors.
Applied Physics Letters | Year: 2012

The excitation of surface plasmon polaritons by focusing a laser beam onto a hole pair in a thin gold film is studied both experimentally and theoretically. By means of leakage radiation microscopy we quantitatively measure the light-plasmon coupling efficiency as a function of the hole distance. We find a modulation of the coupling efficiency as a function of hole distance that strongly depends on the polarization direction of the incident light, in agreement with theoretical simulations. © 2012 American Institute of Physics.


Simbrunner C.,Johannes Kepler University | Quochi F.,University of Cagliari | Hernandez-Sosa G.,Johannes Kepler University | Oehzelt M.,Johannes Kepler University | And 7 more authors.
ACS Nano | Year: 2010

Self-assembly processes and organic-organic heteroepitaxy are powerful techniques to obtain highly ordered molecular aggregates. Here we demonstrate that combining both methods allows not only to fabricate highly crystalline and uniaxially oriented self-assembled nanofibers but also to tune their polarized emission. We show that submonolayer coverage of sexithiophene on top of para-sexiphenyl nanofibers is sufficient to change their emission color from blue to green. Triband emission in the red, green, and blue is generated in nanofibers with thicker sexithiophene coverage, where layers of co-oriented crystals are separated by green-emitting molecular sheets. © 2010 American Chemical Society.


Kannan R.,Bishop Heber College | Andres F.,Japan National Institute of Information and Communications Technology | Guetl C.,Graz University of Technology
Multimedia Tools and Applications | Year: 2010

A well-annotated dance media is an essential part of a nation's identity, transcending cultural and language barriers. Many dance video archives suffer from problems concerning authoring and access, because of the complex spatio-temporal relationships that exist between the dancers in terms of movements of their body parts and the emotions expressed by them in a dance. This paper presents a system named DanVideo for semi-automatic authoring and access to dance archives. DanVideo provides methods of annotation and authoring and retrieval tools for choreographers, dancers, and students. We demonstrate how dance media can be semantically annotated and how this information can be used for the retrieval of the dance video semantics. In particular, DanVideo offers an MPEG-7 based semi-automatic authoring tool that takes dance video annotations generated by dance experts and produces MPEG-7 metadata. DanVideo also has a search engine that takes users' queries and retrieves dance semantics from metadata arranged using tree-embedding technique and based on spatial, temporal and spatio-temporal features of dancers. The search engine also leverages a domain-specific ontology to process knowledge-based queries. We have assessed the dance-video queries and semantic annotations in terms of precision, recall, and fidelity. © 2009 Springer Science+Business Media, LLC.


Reichert J.L.,University of Graz | Kober S.E.,University of Graz | Neuper C.,University of Graz | Neuper C.,Graz University of Technology | Wood G.,University of Graz
Clinical Neurophysiology | Year: 2015

Objective: Instrumental conditioning of EEG activity (EEG-IC) is a promising method for improvement and rehabilitation of cognitive functions. However, it has been found that even healthy adults are not always able to learn how to regulate their brain activity during EEG-IC. In the present study, the role of a neurophysiological predictor of EEG-IC learning performance, the resting-state power of sensorimotor rhythm (rs-SMR, 12-15. Hz), was investigated. Methods: Eyes-open and eyes-closed rs-SMR power was assessed before N= 28 healthy adults underwent 10 training sessions of instrumental SMR conditioning (ISC), in which participants should learn to voluntarily increase their SMR power by means of audio-visual feedback. A control group of N= 19 participants received gamma (40-43. Hz) or sham EEG-IC. Results: N= 19 of the ISC participants could be classified as "responders" as they were able to increase SMR power during training sessions, while N= 9 participants ("non-responders") were not able to increase SMR power. Rs-SMR power in responders before start of ISC was higher in widespread parieto-occipital areas than in non-responders. A discriminant analysis indicated that eyes-open rs-SMR power in a central brain region specifically predicted later ISC performance, but not an increase of SMR in the control group. Conclusions: Together, these findings indicate that rs-SMR power is a specific and easy-to-measure predictor of later ISC learning performance. Significance: The assessment of factors that influence the ability to regulate brain activity is of high relevance, as it could be used to avoid potentially frustrating and expensive EEG-IC training sessions for participants who have a low chance of success. © 2015 International Federation of Clinical Neurophysiology.


Holzman R.,Carnegie Mellon University | Howard D.,Colgate University | Sprussel P.,Graz University of Technology
Electronic Journal of Combinatorics | Year: 2015

We study a generalization of the notion of coloring of graphs, similar in spirit to that of list colorings: a cooperative coloring of a family of graphs G1,G2,….,Gk on the same vertex set V is a choice of independent sets Ai in Gi (1 ≤ i ≤ k) such that ∪ki=1 Ai = V. This notion is linked (with translation in both directions) to the notion of ISRs, which are choice functions on given sets, whose range belongs to some simplicial complex. When the complex is that of the independent sets in a graph G, an ISR for a partition of the vertex set of G into sets V1,….,Vn is a choice of a vertex vi ∈ Vi for each i such that {v1,…,vn} is independent in G. Using topological tools, we study degree conditions for the existence of cooperative colorings and of ISRs. A sample result: Three cycles on the same vertex set have a cooperative coloring. © 2015, Australian National University. All rights reserved.


Unterweger H.,Graz University of Technology
Proceedings of SDSS' Rio 2010: International Colloquium Stability and Ductility of Steel Structures | Year: 2010

In building constructions for bracing members often hollow sections are used with slotted gusset plates at the ends. These plates are attached to non-stiffened plates of the adjacent construction. In practice sometimes a nearly centered joint is designed, by arranging the slotted gusset plate with an eccentricity of half the plate thickness to the member axis, so that the member eccentricity is minimised. In the paper the load bearing behaviour of such members under compression and tension is discussed based on numerical analysis with nonlinear FE - models including imperfections. The geometric parameters and boundary conditions are varied in such a way that practical cases are covered and that the typical load bearing behaviour can be seen. Based on these results an engineering model for the design in practice is represented. © (2010) by COPPE - Federal University of Rio de Janeiro All rights reserved.


Loginov E.,Ecole Polytechnique Federale de Lausanne | Callegari C.,Graz University of Technology | Callegari C.,Elettra - Sincrotrone Trieste | Ancilotto F.,University of Padua | And 2 more authors.
Journal of Physical Chemistry A | Year: 2011

One- and two-photon excitation spectra of sodium atoms on the surface of helium droplets are reported. The spectra are recorded by monitoring the photoionization yield of desorbed atoms as function of excitation frequency. The excitation spectra involving states with principal quantum number up to n = 6 can be reproduced by a pseudodiatomic model where the helium droplet is treated as a single atom. For the lowest excited states of sodium, the effective interaction potentials for this system can be approximated by the sum of NaHe pair potentials. For the higher excited states, the interaction of the sodium valence electron with the helium induces significant configuration mixing, leading to a failure of this approach. For these states, effective interaction potentials based on a perturbative treatment of the interactions between the valence electron, the alkali positive core, and the helium, as described in detail in the accompanying publication, yield excellent agreement with experiment. © 2011 American Chemical Society.


Callegari C.,Graz University of Technology | Callegari C.,Elettra - Sincrotrone Trieste | Ancilotto F.,University of Padua | Ancilotto F.,CNR Institute of Materials
Journal of Physical Chemistry A | Year: 2011

A method is proposed for the calculation of potential energy curves and related electronic excitation spectra of dopant atoms captured in/on He nanodroplets and is applied to alkali metal atoms. The method requires knowledge of the droplet density distribution at equilibrium (here calculated within a bosonic-He density functional approach) and of a set of valence electron orbitals of the bare dopant atom (here calculated by numeric solution of the Schrödinger equation in a suitably parametrized model potential). The electron-helium interaction is added as a perturbation, and potential energy curves are obtained by numeric diagonalization of the resulting Hamiltonian as a function of an effective coordinate zA (here the distance between the dopant atom and center of mass of the droplet, resulting in a pseudodiatomic potential). Excitation spectra are calculated for Na in the companion paper as the Franck-Condon factors between the v = 0 vibrational state in the ground electronic state and excited states of the pseudodiatomic molecule. They agree well with available experimental data, even for highly excited states where a more traditional approach fails. © 2011 American Chemical Society.


Kober S.E.,University of Graz | Kober S.E.,Universitaetsplatz 3 | Witte M.,University of Graz | Stangl M.,University of Graz | And 6 more authors.
Clinical Neurophysiology | Year: 2015

Objective: In the present study, we investigated how the electrical activity in the sensorimotor cortex contributes to improved cognitive processing capabilities and how SMR (sensorimotor rhythm, 12-15. Hz) neurofeedback training modulates it. Previous evidence indicates that higher levels of SMR activity reduce sensorimotor interference and thereby promote cognitive processing. Methods: Participants were randomly assigned to two groups, one experimental (N=10) group receiving SMR neurofeedback training, in which they learned to voluntarily increase SMR, and one control group (N=10) receiving sham feedback. Multiple cognitive functions and electrophysiological correlates of cognitive processing were assessed before and after 10 neurofeedback training sessions. Results: The experimental group but not the control group showed linear increases in SMR power over training runs, which was associated with behavioural improvements in memory and attentional performance. Additionally, increasing SMR led to a more salient stimulus processing as indicated by increased N1 and P3 event-related potential amplitudes after the training as compared to the pre-test. Finally, functional brain connectivity between motor areas and visual processing areas was reduced after SMR training indicating reduced sensorimotor interference. Conclusions: These results indicate that SMR neurofeedback improves stimulus processing capabilities and consequently leads to improvements in cognitive performance. Significance: The present findings contribute to a better understanding of the mechanisms underlying SMR neurofeedback training and cognitive processing and implicate that SMR neurofeedback might be an effective cognitive training tool. © 2014 International Federation of Clinical Neurophysiology.


Seifried B.,Graz University of Technology | Temelli F.,University of Alberta
INFORM - International News on Fats, Oils and Related Materials | Year: 2010

Some of the unique properties of carbon dioxide (CO 2)-expanded (CX) lipids are discussed. Lipids, such as triglycerides (TO) and fatty acid ethyl esters (FAEE), can dissolve large amounts of CO2 when exposed to pressurized CO2. As a result, the lipids expand in volume, and concomitantly their physical properties also change with temperature and pressure. The dissolution of large amounts of CO2 in lipids at elevated pressures leads to both volumetric expansion and a pronounced change in physical properties, such as density, interfacial tension (IFT), and viscosity. The reduced viscosity could accelerate the reaction rates in heterogeneously catalyzed reactions, especially in the case of highly viscous oils. Reduced interfacial tension and reduced viscosity may be advantageous for applications involving formation of droplets in spray processes aiming at increasing the interphase, which may be desirable in lipid extraction and purification using pressurized CO2.


Kaafarani B.R.,American University of Beirut | El-Ballouli A.O.,American University of Beirut | Trattnig R.,NanoTecCenter Weiz Forschungsgesellschaft mbH | Fonari A.,New Mexico Highlands University | And 11 more authors.
Journal of Materials Chemistry C | Year: 2013

Tetrahydropyrene and pyrene have been functionalized in their 2,7-positions with carbazole and 3,6-di-tert-butylcarbazole groups, and the properties of these new compounds are compared to analogous carbazole and 3,6-di-tert- butylcarbazole derivatives of benzene and biphenyl using X-ray crystallography, UV-vis absorption and fluorescence spectroscopy, electrochemistry, and quantum-chemical calculations. The absorption spectra are similar to those of their biphenyl-bridged analogues, although TD-DFT calculations indicate a different description of the excited states in the pyrene case, with the lowest observed absorption no longer corresponding to the S0 → S 1 transition. The 3,6-di-tert-butylcarbazole compounds show reversible electrochemical oxidations; the benzene, biphenyl, tetrahydropyrene, or pyrene bridging groups have little impact on the first oxidation potential. Bilayer organic light-emitting diodes incorporating the tetrahydropyrene and pyrene derivatives as emitters show deep-blue electroluminescence. This journal is © The Royal Society of Chemistry 2013.


In the course of increasing thermal upgrades of existing buildings, interior insulation is in many cases the only way of achieving a substantial increase in comfort and safeguarding the value of the building. In recent years, numerous diffusion-open, capillary-active systems have appeared on the market, one of which is presented in the following, a system with a number of special characteristics and a wide range of possible applications. Since its development in collaboration with Joanneum Research and the CelluloseProduktionHartberg - CPH company under a subsidised research project, the spray-on rendered cellulose insulation has been refined in three further subsidised projects headed by the Institute of Building Construction at Graz University of Technology in cooperation with renowned national and international partners and tested by means of long-term in situ measurements combined with transient hygrothermal simulation calculations. Most recently in a comparison with four other interior insulation systems regarded as ecological and diffusion-open based on the integration of timber beams, a particularly critical factor. Even though the application is highly demanding, it was possible to demonstrate the suitability of spray-on rendered recycled paper cellulose as diffusion-open interior insulation without a vapour barrier even with integrated timber beams. The system is thus recommended for thermal upgrade of extremely uneven or curved structures. © 2016 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.


Morandi O.,Graz University of Technology | Morandi O.,CNRS Institute of Genetics and of Molecular and Cellular Biology
Journal of Physics A: Mathematical and Theoretical | Year: 2010

A model for the evolution of a quantum particle in the phase plane is derived. The quasi-distribution function is decomposed into a suitable over-complete basis of coherent states. In this approach, a coarse grain length scale is introduced by using the spread of the coherent states. The obtained evolution system is completely equivalent to the Wigner formulation of the quantum mechanics. It shows some analogy with the von Neumann approach and the particle in the cell method in classical plasma physics. Differing from the usual formulation of the quantum phase space, given in terms of infinite-order partial differential equations, in this model, the evolution equations of the second differential order are expressed by a hierarchy of coupled functions (the first term being the Husimi function). The resulting formulation reveals itself to be particularly close to the classical description of the particles motion. This formal analogy is useful to gain new physical insights and to profit from numerical methods developed for classical systems. © 2010 IOP Publishing Ltd.


Giovannetti G.,International School for Advanced Studies | Aichhorn M.,Graz University of Technology | Capone M.,International School for Advanced Studies
Physical Review B - Condensed Matter and Materials Physics | Year: 2014

We employ a combination of density functional theory and dynamical mean-field theory to investigate the electronic structure of the recently synthesized insulator BaCrO3. Our calculations show that Hund's coupling is responsible for strong correlation effects, which are however not sufficient to turn the system insulating without breaking any symmetry. The Hund's correlated metal is however unstable with respect to orbital ordering, which indeed makes the system insulating. The orbitally ordered insulator favors Jahn-Teller distortions and a secondary magnetic ordering. © 2014 American Physical Society.


Stelzmann E.,Graz University of Technology
2011 IEEE International Systems Conference, SysCon 2011 - Proceedings | Year: 2011

Several agile methods were proposed that should provide more agility for Systems Engineering. But there was little discussion about the right context for Agile Systems Engineering. This paper shows under which conditions the main principle of agile development can be applied successfully. Therefore prior research about context of agile software development is reviewed. Additionally 20 system developing companies are being interviewed. A classification scheme that divides the context into feasibility and demand for agility is presented. Also contextual factors are listed to classify companies or projects within this scheme. Real company examples are demonstrated for the different situations in this scheme. And recommendations concerning agility are given. © 2011 IEEE.


Cela E.,Graz University of Technology | Stanek R.,University of Graz
Journal of Combinatorial Optimization | Year: 2013

The data arrangement problem on regular trees (DAPT) consists in assigning the vertices of a given graph G to the leaves of a d-regular tree T such that the sum of the pairwise distances of all pairs of leaves in T which correspond to edges of G is minimised. This problem is a special case of the generic graph embedding problem and is NP-hard for every fixed {Mathematical expression}. In this paper we propose construction and local search heuristics for the DAPT and introduce a lower bound for this problem. The analysis of the performance of the heuristics is based on two considerations: (a) the quality of the solutions produced by the heuristics as compared to the respective lower bound (b) for a special class of instances with known optimal solution we evaluate the gap between the optimal value of the objective function and the objective function value attained by the heuristic solution, respectively. © 2013 Springer Science+Business Media New York.


Kerber M.,Graz University of Technology | Sheeny D.R.,University of Connecticut | Skraba P.,Jozef Stefan Institute
Proceedings of the Annual ACM-SIAM Symposium on Discrete Algorithms | Year: 2016

Nested dissection exploits the underlying topology to do matrix reductions while persistent homology exploits matrix reductions to the reveal underlying topology. It seems natural that one should be able to combine these techniques to beat the currently best bound of matrix multiplication time for computing persistent homology. However, nested dissection works by fixing a reduction order, whereas persistent homology generally constrains the ordering according to an input filtration. Despite this obstruction, we show that it is possible to combine these two theories. This shows that one can improve the computation of persistent homology if the underlying space has some additional structure. We give reasonable geometric conditions under which one can beat the matrix multiplication bound for persistent homology. © Copyright (2016) by SIAM: Society for Industrial and Applied Mathematics.


Goller M.,RF-iT Solutions | Brandner M.,Graz University of Technology
2011 IEEE International Conference on RFID-Technologies and Applications, RFID-TA 2011 | Year: 2011

Radio Frequency Identification has gained increasing popularity in the logistic sector as a tool to locate and track individual items throughout complex processes. A characteristic of RFID systems is that both read events and business processes can be subjected to uncertainties. In this work we present a novel modeling approach for RFID processes and supply chains. The proposed model considers typical trajectories of tags through a business process and can be used to improve the detection performance of individual RFID gates. Consequently, this improves the robustness of the overall RFID system. © 2011 IEEE.


Dominikus S.,Graz University of Technology
2011 IEEE International Conference on RFID-Technologies and Applications, RFID-TA 2011 | Year: 2011

Privacy is an important aspect in the Internet of Things (IoT). We see the provision of privacy preserving mechanisms as one enabler for this technology (above all because of the public acceptance). Privacy means, that a user has control over the access to its data. In this work we want to present a medical application which uses passive RFID tags on pharmaceuticals to provide special services for the user. We consider this information as sensible and developed a system where the user has the full control over the access to this data. For our protocol we use standardized cryptographic primitives which are suitable for passive RFID technology. Our protocol provides data privacy as well as transfer of ownership. © 2011 IEEE.


Stogmuller P.,Inocon Technology GmbH | Hinterer A.,Inocon Technology GmbH | Pesendorfer F.,Inocon Technology GmbH | Enzinger N.,Graz University of Technology
Materialpruefung/Materials Testing | Year: 2015

The atmospheric plasma spray (APS) process for applying thin coatings on substrates has a lot of different process parameters. To evaluate which parameters have the most significant influence on the adhesive strength, a design of experience (DoE) investigation was performed. The data for the DoE analyses were generated with an own designed adhesive tensile strength test device according to EN 13144. For these experiments, the two component epoxy HTK Ultra Bond 100 was used for loading the interface of APS zinc coated steel samples. To provide a highly repeatable test setup, a special gluing device was developed to cope with the requirements of the Ultra Bond 100. Although the DoE analysis showed the expected results, the pull-off test has some weaknesses, which are shown and discussed in the present paper. © Carl Hanser Verlag München.


Volkmann G.M.,DYWIDAG Systems International GmbH | Schubert W.,Graz University of Technology
14th Australasian Tunnelling Conference 2011: Development of Underground Space, Proceedings | Year: 2011

Pipe umbrella systems have effectively been used as an additional support system in the working area in weak ground conditions during the last decades. Thus, a considerable number of applications accounts in urban tunnelling with shallow overburden. However, this support system is also successfully used when a tunnel alignment crosses fault zones, sediments, moraines or talus with overburdens from shallow to deep. The pipe umbrella support system itself is termed differently worldwide - synonyms are canopy tube umbrella method, umbrella arch method, or long fore-poling method. One main reason for the increase in application is that this support system closes cost-effectively the gap between reasonable, normal supported tunnels and tunnels supported with more expensive special techniques like horizontal jet-grouting or ground freezing. By using this system, many projects can be built more cost effective without decreasing the common level of safety. The pipe umbrella construction method is pretty young, so the knowledge about this system has been intensely researched in the last decade. This led to an enormous increase in understanding the interaction between support system and surrounding ground, the mode of action, and the important details for construction. Pipe umbrella support systems are applied in difficult ground conditions, so a special developed measurement arrangement was used to observe deformations ahead of the working face during tunnelling. The evaluation of collected data sets identified that cased-drilling systems have clear advantages compared to predrilling systems during the installation process in weak ground conditions. This may become important depending on project requirements, so this difference must be considered in design as well as in the tender document specifications.


Peharz R.,Medical University of Graz | Tschiatschek S.,ETH Zurich | Pernkopf F.,Graz University of Technology | Domingos P.,University of Washington
Journal of Machine Learning Research | Year: 2015

Sum-product networks (SPNs) are a promising avenue for probabilistic modeling and have been successfully applied to various tasks. However, some theoretic properties about SPNs are not yet well understood. In this paper we fill some gaps in the theoretic foundation of SPNs. First, we show that the weights of any complete and consistent SPN can be transformed into locally normalized weights without changing the SPN distribu-tion. Second, we show that consistent SPNs cannot model distributions significantly (ex-ponentially) more compactly than decompos-able SPNs. As a third contribution, we ex-tend the inference mechanisms known for SPNs with finite states to generalized SPNs with arbitrary input distributions. Copyright 2015 by the authors.


Potkonjak V.,University of Belgrade | Gardner M.,University of Essex | Callaghan V.,University of Essex | Mattila P.,University of Oulu | And 4 more authors.
Computers and Education | Year: 2016

Within education, concepts such as distance learning, and open universities, are now becoming more widely used for teaching and learning. However, due to the nature of the subject domain, the teaching of Science, Technology, and Engineering are still relatively behind when using new technological approaches (particularly for online distance learning). The reason for this discrepancy lies in the fact that these fields often require laboratory exercises to provide effective skill acquisition and hands-on experience. Often it is difficult to make these laboratories accessible for online access. Either the real lab needs to be enabled for remote access or it needs to be replicated as a fully software-based virtual lab. We argue for the latter concept since it offers some advantages over remotely controlled real labs, which will be elaborated further in this paper. We are now seeing new emerging technologies that can overcome some of the potential difficulties in this area. These include: computer graphics, augmented reality, computational dynamics, and virtual worlds. This paper summarizes the state of the art in virtual laboratories and virtual worlds in the fields of science, technology, and engineering. The main research activity in these fields is discussed but special emphasis is put on the field of robotics due to the maturity of this area within the virtual-education community. This is not a coincidence; starting from its widely multidisciplinary character, robotics is a perfect example where all the other fields of engineering and physics can contribute. Thus, the use of virtual labs for other scientific and non-robotic engineering uses can be seen to share many of the same learning processes. This can include supporting the introduction of new concepts as part of learning about science and technology, and introducing more general engineering knowledge, through to supporting more constructive (and collaborative) education and training activities in a more complex engineering topic such as robotics. The objective of this paper is to outline this problem space in more detail and to create a valuable source of information that can help to define the starting position for future research. © 2016 Elsevier Ltd. All rights reserved.


Breitwieser D.,University of Graz | Spirk S.,University of Maribor | Spirk S.,Graz University of Technology | Fasl H.,University of Graz | And 7 more authors.
Journal of Materials Chemistry B | Year: 2013

The rational design of silver nanoparticles encapsulated in an anticoagulant, hemocompatible polysaccharide, 6-O-chitosan sulfate, is presented. Three different approaches are described for the immobilization of these core shell particles on cellulosic surfaces. The mass of the immobilized particles is quantified using a quartz crystal microbalance with dissipation (QCM-D). The antimicrobial activity of the surfaces towards E. coli MG 1655 [R1-16] is investigated by live/dead assays using fluorescence staining. All surfaces treated with the designed nanoparticles exhibit excellent antimicrobial activity towards E. coli MG 1655 [R1-16]. Anticoagulant properties of blood plasma on the nanoparticle treated surfaces have been determined using QCM-D. In comparison with the unmodified substrates, the total coagulation time as well as the thrombin formation time and fibrin clotting time of surfaces modified with nanoparticles are significantly increased. This journal is © 2013 The Royal Society of Chemistry.


In Europe a harmonisation in the measurement of particle size distribution of the fine earth soils and fine sediments is needed. Both parameters, texture and texture classes, are the base for statistically resilient and justiciable criteria related to heavy metal, nutrient and water contents. Spatially dominating primary data of the Austrian and German Soil Assessment is taken for an approach to discuss about regulations concerning particle-size fractions and particle-size classes overlapping the band of soil functions, soil law and land use. An inventory of verified and validated primary particle size parameters has to be done to make conclusions based on referenced materials of fine earth and sediments within national programs for example as irrigation control (STEINITZER, 1999) or ecotoxicological impacts of chemicals on soils (BLUM, 1999).


Birkl C.,Medical University of Graz | Langkammer C.,Medical University of Graz | Krenn H.,University of Graz | Goessler W.,University of Graz | And 5 more authors.
Magnetic Resonance in Medicine | Year: 2015

Purpose: The assessment of iron content in brain white matter (WM) is of high importance for studying neurodegenerative diseases. While R2∗ mapping and quantitative susceptibility mapping is suitable for iron mapping in gray matter, iron mapping in WM still remains an unsolved problem. We propose a new approach for iron mapping, independent of diamagnetic contributions of myelin by assessing the temperature dependency of the paramagnetic susceptibility. Theory and Methods: We used unfixed human brain slices for relaxometry and calculated R2′ as a measure for microscopic susceptibility variations at several temperatures (4°C-37°C) at 3 Tesla. The temperature coefficient of R2′ (TcR2p) was calculated by linear regression and related to the iron concentration found by subsequent superconducting quantum interference device (SQUID) magnetometry and by inductively coupled plasma mass spectrometry. Results: In line with SQUID measurements, R2′ mapping showed a linear temperature dependency of the bulk susceptibility with the highest slope in gray matter. Even in WM, TcR2p yielded a high linear correlation with the absolute iron concentration. Conclusion: According to Curie's law, only paramagnetic matter exhibits a temperature dependency while the diamagnetism shows no effect. We have demonstrated that the temperature coefficient (TcR2p) can be used as a measure of the paramagnetic susceptibility despite of an unknown diamagnetic background. © 2014 Wiley Periodicals, Inc.


Ulsrud K.,University of Oslo | Winther T.,University of Oslo | Palit D.,TERI University | Rohracher H.,Graz University of Technology | Sandgren J.,Sweco Norway AS
Energy for Sustainable Development | Year: 2011

The article presents new empirical material from a case study on longstanding, pioneering efforts on implementation and use of solar mini-grid systems in the Sunderban Islands in India. These local, socio-technical experiments have been investigated by a trans-disciplinary team of researchers and practitioners in order to gain a deep understanding of the diversity of social and technical factors influencing the ways in which the systems work at different levels. This socio-technical research highlights the dynamics between technology and society and how they are mutually influencing and shaping each other. These dynamics create gradual changes in the socio-technical system of technical devises, people, practices, knowledge and other elements, requiring adjustments also by the implementing actors. A range of technical and non-technical factors at various levels are found to be relevant for the implementation, operation, sustenance and further development of the solar power supply systems. The research points to important factors that should be taken into account and considered when planning similar activities. In addition to the analysis of the research findings, the article includes a brief review of literature on the implementation and use of solar photovoltaic technology in developing countries, with an emphasis on solar mini-grid systems. © 2011 International Energy Initiative.


Holzapfel G.A.,Graz University of Technology | Holzapfel G.A.,KTH Royal Institute of Technology | Ogden R.W.,University of Glasgow
Journal of the Royal Society Interface | Year: 2010

This paper provides the first analysis of the three-dimensional state of residual stress and stretch in an artery wall consisting of three layers (intima, media and adventitia), modelled as a circular cylindrical tube. The analysis is based on experimental results on human aortas with non-atherosclerotic intimal thickening documented in a recent paper by Holzapfel et al. (Holzapfel et al. 2007 Ann. Biomed. Eng. 35, 530-545 (doi:10.1007/s10439-006-9252-z)). The intima is included in the analysis because it has significant thickness and load-bearing capacity, unlike in a young, healthy human aorta. The mathematical model takes account of bending and stretching in both the circumferential and axial directions in each layer of the wall. Previous analysis of residual stress was essentially based on a simple application of the opening-angle method, which cannot accommodate the three-dimensional residual stretch and stress states observed in experiments. The geometry and nonlinear kinematics of the intima, media and adventitia are derived and the associated stress components determined explicitly using the nonlinear theory of elasticity. The theoretical results are then combined with the mean numerical values of the geometrical parameters and material constants from the experiments to illustrate the three-dimensional distributions of the stretches and stresses throughout the wall. The results highlight the compressive nature of the circumferential stress in the intima, which may be associated with buckling of the intima and its delamination from the media, and show that the qualitative features of the stretch and stress distributions in the media and adventitia are unaffected by the presence or absence of the intima. The circumferential residual stress in the intima increases significantly as the associated residual deformation in the intima increases while the corresponding stress in the media (which is compressive at its inner boundary and tensile at its outer boundary) is only slightly affected. The theoretical framework developed herein enables the state of residual stress to be calculated directly, serves to improve insight into the mechanical response of an unloaded artery wall and can be extended to accommodate more general geometries, kinematics and states of residual stress as well as more general constitutive models. © 2009 The Royal Society.


Taherkordi A.,University of Oslo | Johansen C.,University of Oslo | Eliassen F.,University of Oslo | Romer K.,Graz University of Technology
Proceedings - IEEE International Conference on Distributed Computing in Sensor Systems, DCOSS 2015 | Year: 2015

The development of resource-constrained embedded systems that are naturally state-driven is still a challenging issue, especially in industrial applications - developed on a bare-bone style runtime system with basic programming features. This is because of the complexity of state-driven design in embedded applications, such as parallel and complicated event-based activity flows, and complicated constraints for transitioning between program states. State machines are considered a systematic approach for such needs. However, existing approaches, in this area, either do not satisfactorily address the above complexity aspects, or force the developer to write code intermingling state handling logic with the functional code. To tackle these issues, we propose TOKEN IT, a state machine-based development framework for resource-constrained embedded systems. Using TOKEN IT, the programmer models the application as a set of parallel processes, where each process consists of sequenced activities with state constraints such as delayed transitions or interdependency between the states of parallel processes. TOKEN IT, then, processes the obtained model and associates a token to each sequential flow of activities, synthesizing them and executing state transitions according to the constraints expressed in the TOKEN IT model. The evaluation results show that TOKEN IT reduces significantly the complexity of state-driven programming in embedded systems at an acceptable memory cost and with no extra processing overhead. © 2015 IEEE.


Lorber F.,Graz University of Technology
2015 IEEE 8th International Conference on Software Testing, Verification and Validation, ICST 2015 - Proceedings | Year: 2015

A lot of systems nowadays, especially in safety-critical areas, have to comply to very strict real-time requirements. Deviation from the specified time behavior can lead to severe faults. Thus the components need to be thoroughly tested to ensure a high quality standard. Model-based testing is a popular technology for automatic and systematic test-case generation, where a system-under-test is tested for conformance with a model that specifies its intended behavior. Model-based mutation testing is a specific fault-oriented variant of model- based testing. In this variant of testing, the test case generation is guided by a mutant, an intentionally altered version of the original model that specifies a common modeling error, to generate a specific test case capable of identifying that error. In the presented thesis we investigate ways to apply model-based mutation testing to real-time applications. The plan is to investigate two specification languages: timed automata and timed contracts. We already developed an algorithm and an implementation for testing deterministic timed automata and a theory and implementation for untimed contracts. In the last year of the thesis we will concentrate on determinizing timed automata restricted to the bounded case, supporting the test-case generation from networks of timed automata and adding real-time support to our contract-based testing tool. The final step of the thesis will be the evaluation on industrial case studies. © 2015 IEEE.


Hetzner S.,Friedrich - Alexander - University, Erlangen - Nuremberg | Steiner C.M.,Graz University of Technology | Dimitrova V.,University of Leeds | Brna P.,University of Leeds | Conlan O.,Trinity College Dublin
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2011

This research considers the application of simulated environments for adult training, and adopts the view that effective adaptive solutions for adults should be underpinned by appropriate adult learning theories. Such environments should offer learning experiences tailored to the way adults learn: self-directed, experienced-based, goal- and relevancy oriented. This puts andragogy and self-regulated learning at the heart of the pedagogical underpinnings of the intelligent augmentation of simulated environments for experiential learning. The paper presents a holistic approach for augmented simulated experiential learning. Based on andragogic principles, we draw generic requirements for augmented simulated environments for adult learning. An extended self-regulated learning model that links experiences in simulated and real world is then presented. A holistic framework for augmenting simulators - SRL-A-LRS - is presented and illustrated in the context of the ImREAL EU project. This points at a radically new approach for augmenting simulated systems for adult experiential learning. © 2011 Springer-Verlag Berlin Heidelberg.


Tskhakaya Sr. D.D.,University of Innsbruck | Tskhakaya Sr. D.D.,Georgian Academy of Sciences | Kos L.,University of Ljubljana | Jelic N.,Graz University of Technology
Physics of Plasmas | Year: 2014

The paper presents a comprehensive kinetic theory of the famous Tonks-Langmuir model of a plane symmetric discharge, taking into account the thermal motion of ion source particles. The ion kinetics is governed by the ionization of neutrals at electron impacts. The plasma consisting of Boltzmann distributed electrons and singly charged ions is in contact with the absorbing negative wall. The derivations are performed in the frame of the "asymptotic two-scale" approximation, when the ionization mean-free path Li is much larger than the electron Debye length λD. In the limit (λD/Li)→ 0, the plasma-wall transition (PWT) layer can be split into two sublayers: a quasineutral presheath (PS) (with the scale-length Li) and the Debye sheath (DS) (with the scale λD). Such a subdivision of the PWT layer allows to investigate these sublayers separately and simplify the analysis of the influence of the ion source thermal motion (this has been neglected in the major part of publications up to now). The uniform description of the PWT layer as a single unit is complicated by the singular presheath and sheath structure and by a coupling with the eigenvalue problem originating from the plasma balance in the bounded system. The issue is clarified both analytically and numerically by construction of a matched asymptotic expressions. The equation and the length-scale governing the transition between neighboring PS and DS sublayers are derived. The eigenvalue problem combining the wall potential, the wall location, and the ionization mean-free path is discussed. © 2014 AIP Publishing LLC.


Massoud S.S.,University of Louisiana at Lafayette | Louka F.R.,University of Louisiana at Lafayette | Obaid Y.K.,University of Louisiana at Lafayette | Vicente R.,University of Barcelona | And 3 more authors.
Dalton Transactions | Year: 2013

The reaction of a methanolic solution containing M(ClO4) 2·nH2O (M = Cu, Ni, Zn or Cd) or CoCl 2·6H2O with bis(2-(3,5-dimethyl-1H-pyrazol-1-yl) ethyl)amine (bedmpza) in the presence of NaN3 afforded the complexes [Cu(bedmpza)(μ1,1-N3)]2(ClO 4)2 (1), [Ni(bedmpza)(N3)(μ1,1- N3)]2·1.5H2O (2), [Co(bedmpza)(N 3)2] (3), [Zn(bedmpza)(N3)]ClO4 (4) and [Cd(bedmpza)(N3)(μ1,1-N3)] 2·1.5H2O (5). The five complexes were characterized by spectroscopic techniques and their molecular structures were determined by single crystal X-ray crystallography. The two mononuclear complexes 3 and 4 display distorted TBP and tetrahedral geometry, respectively with the azide ions acting as monodentate ligands. Doubly bridged end-on-azido dinuclear complexes were obtained in the remaining compounds. Compounds 2 and 5 are isomorphic with distorted octahedral geometry, whereas distorted square pyramidal geometry was determined in the Cu(ii) complex 1. The magnetic properties for complexes 1 and 2 were investigated by measuring the magnetic susceptibilities at variable temperatures (300-2 K). The Ni(ii) complex exhibits moderate ferromagnetic coupling, whereas [Cu(bedmpza)(μ1,1-N3)] 2(ClO4)2 (1) which contains two crystallographic independent dinuclear subunits in the unit cell, with different Cu-N(N3)-Cu bond angles, reveals different signs in the magnetic coupling. The complex represents the first example in the literature that has simultaneously two moieties with ferro- (J = 15.4 cm-1) and antiferromagnetic (J = -18.9 cm-1) interactions. This journal is © 2013 The Royal Society of Chemistry.


Hutter M.,Graz University of Technology | Joye M.,Content Security | Sierra Y.,Oberthur Technologies
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2011

It has been recently shown that sharing a common coordinate in elliptic curve cryptography implementations improves the performance of scalar multiplication. This paper presents new formulæ for elliptic curves over prime fields that provide efficient point addition and doubling using the Montgomery ladder. All computations are performed in a common projective Z-coordinate representation to reduce the memory requirements of low-resource implementations. In addition, all given formulæ make only use of out-of-place operations therefore insuring that it requires no additional memory for any implementation of the underlying finite-field operations whatsoever. Our results outperform existing solutions in terms of memory and speed and allow a fast and secure implementation suitable for low-resource devices and embedded systems. © 2011 Springer-Verlag.


Steiner K.,Austrian Center of Industrial Biotechnology | Schwab H.,Austrian Center of Industrial Biotechnology | Schwab H.,Graz University of Technology
Computational and Structural Biotechnology Journal | Year: 2012

Enzymes are an attractive alternative in the asymmetric syntheses of chiral building blocks. To meet the requirements of industrial biotechnology and to introduce new functionalities, the enzymes need to be optimized by protein engineering. This article specifically reviews rational approaches for enzyme engineering and de novo enzyme design involving structure-based approaches developed in recent years for improvement of the enzymes' performance, broadened substrate range, and creation of novel functionalities to obtain products with high added value for industrial applications.


Rahimipour S.,Bar - Ilan University | Gescheidt G.,Graz University of Technology | Bilkis I.,Hebrew University of Jerusalem | Fridkin M.,Weizmann Institute of Science | Weiner L.,Weizmann Institute of Science
Applied Magnetic Resonance | Year: 2010

In this review article, the structure, properties, stability and biological application of redox-active quinones are presented. A series of quinoid molecules is evaluated in terms of their ability to act as electron-transfer active compounds using cyclovoltammetric, electron paramagnetic resonance (EPR) and spin-trapping techniques. Redox potentials and electron distribution of the intermediate radical anions are shown to be decisive factors for the generation of reactive oxygen species (ROS). Mechanisms of ROS generation in dark by biological electron-transfer reaction or under photoexcitation have been proposed and experimentally verified. For site-specific damage of tumors, some quinone derivatives were covalently bound with the luteinizing hormone-releasing hormone (LH-RH or GnRH) that produces specific complexes with receptors on the surface of cancer cells. The properties of obtained conjugates to be bound with the different lines of cancer cells (αT3-1, M2R, LNCaP) were tested. EPR was used for the estimation of efficacy of ROS production by the conjugates in solution and in the complex with cancer cells. The toxicity of these conjugates as well as their stability in the stimulated oxidative stress were tested. The proposed approach could be useful in creating a new family of addressed anti-cancer drugs, including compounds for the treatment of tumors by photodynamic therapy. © Springer 2009.


Steinbauer F.,Graz University of Technology | Kroll M.,Know Center Gmbaz
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2016

Social media monitoring has become an important means for business analytics and trend detection, for instance, analyzing the sentiment towards a certain product or decision. While a lot of work has been dedicated to analyze sentiment for English texts, much less effort has been put into providing accurate sentiment classification for the German language. In this paper, we analyze three established classifiers for the German language with respect to Facebook posts. We then present our own hierarchical approach to classify sentiment and evaluate it using a data set of ~640 Facebook posts from corporate as well as governmental Facebook pages. We compare our approach to three sentiment classifiers for German, i.e. AlchemyAPI, Semantria and SentiStrength. With an accuracy of 70 %, our approach performs better than the other classifiers. In an application scenario, we demonstrate our classifierl’s ability to monitor changes in sentiment with respect to the refugee crisis. © Springer International Publishing Switzerland 2016.


Uddin Z.,Yanbu University College | Uddin Z.,Graz University of Technology | Uddin Z.,University of Karachi
Chinese Journal of Physics | Year: 2014

Ten new odd levels, of praseodymium I (Pr I), having angular momentum less than 3.5, have been discovered through Fourier transform spectroscopy and presented in this paper. The discovered levels not only explain previously known lines, but also explain some new lines of Pr I. All the new levels together explain fifty-six atomic lines. Previously known classifications of two of the lines of Pr are incorrect, new classifications of these lines have been suggested. © 2014 The physical society of the republic of china.


Unterwieser H.,Holz.bau Forschungs GmbH | Schickhofer G.,Graz University of Technology
European Journal of Wood and Wood Products | Year: 2012

In order to draw conclusions concerning the sound velocity and the dynamic modulus of elasticity of logs and green timber at reference conditions, properties were determined for green timber at temperatures around and below the freezing point. The present investigation includes the analysis of the dependence of sound velocity and dynamic modulus on temperatures between -20 °C and +20 °C and on moisture contents below and above fibre saturation. Sound velocity and dynamic modulus of elasticity were determined based on natural frequency and density. Both sound velocity and dynamic MOE decreased linearly with increasing moisture content and increasing temperature below fibre saturation. Three temperature areas need to be considered above fiber saturation-below -5 °C and above 0 °C and the area between -5 °C and 0 °C. Sound velocity as well as dynamic MOE decrease linearly with increasing temperature. Based on these findings, appropriate adjustment functions for each moisture content and temperature range were found to calculate the dynamic properties at the reference conditions. © Springer-Verlag 2012.


Deineko V.G.,University of Warwick | Klinz B.,Graz University of Technology | Woeginger G.J.,TU Eindhoven
Operations Research Letters | Year: 2013

We analyze the question of deciding whether a quadratic or a hyperbolic 0-1 programming instance has a unique optimal solution. Both uniqueness questions are known to be NP-hard, but are unlikely to be contained in the class NP. We precisely pinpoint their computational complexity by showing that they both are complete for the complexity class Δ2P. © 2013 Elsevier B.V. All rights reserved.


Maly A.,Joanneum Research | Mowlaee P.,Graz University of Technology
ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings | Year: 2016

Conventional single-channel speech enhancement is mainly focused on modifying the noisy short-time Fourier transform amplitude spectrum while for signal reconstruction the noisy phase is used. Recent advances demonstrate the positive improvements in speech enhancement when the noisy phase is replaced with an estimated clean phase for signal reconstruction. In this paper, we study the impact of the linear phase and unwrapped phase components provided by harmonic phase decomposition on the speech quality at signal reconstruction. We present objective and subjective results comparing the proposed harmonic phase modification with other phase estimation methods. Our results show that enhancement of decomposed phase parts suffices for improved reconstruction in speech enhancement. © 2016 IEEE.


Schreuer A.,Graz University of Technology
Energy Research and Social Science | Year: 2016

This paper looks at citizen power plants in Austria - wind farms and photovoltaics plants jointly owned and operated by groups of citizens - and asks whether their establishment can be interpreted as a process of empowerment. To this end I draw on resource-based notions of power, understanding empowerment as the increase of disadvantaged actors' ability to mobilize and use resources for their goals. I argue that the establishment of citizen power plants constitutes a process of successive resource mobilization in which bottom-up actors have been able to access an increasing amount of resources. At first sight this suggests that the establishment of citizen power plants in Austria indeed constitutes a process of empowerment. However, I also discuss three qualifications to such an interpretation. Firstly, the modulation of ends to which resources are put (assimilation and incorporation to established structures); secondly, the persistence of dependency relations for resource access; and thirdly, a bias of citizen power plant initiatives toward already better-resourced individuals and communities. © 2015 Elsevier Ltd. All rights reserved.


Dietsch P.,TU Munich | Brandner R.,Graz University of Technology
Construction and Building Materials | Year: 2015

In timber engineering, self-tapping screws, optimized primarily for axial loading, represent the state-of-the-art in fastener and reinforcement technology. Their economic advantages and comparatively easy handling make them one of the first choices for application in both domains. This paper focuses on self-tapping screws and threaded rods applied as reinforcement, illustrating the state-of-the-art in application and design approaches in Europe, in conjunction with numerous references for background information. With regard to medium to large span timber structures which are predominately erected by using linear timber members, from e.g. glued laminated timber, the focus of this paper is on their reinforcement against stresses perpendicular to grain as well as shear. However, latest findings with respect to cross laminated timber are included as well. © 2015 Elsevier Ltd. All rights reserved.


Seifert C.,Graz University of Technology | Granitzer M.,Know Center GmbH
Proceedings - IEEE International Conference on Data Mining, ICDM | Year: 2010

Active learning has been proven a reliable strategy to reduce manual efforts in training data labeling. Such strategies incorporate the user as oracle: the classifier selects the most appropriate example and the user provides the label. While this approach is tailored towards the classifier, more intelligent input from the user may be beneficial. For instance, given only one example at a time users are hardly able to determine whether this example is an outlier or not. In this paper we propose user-based visually-supported active learning strategies that allow the user to do both, selecting and labeling examples given a trained classifier. While labeling is straightforward, selection takes place using a interactive visualization of the classifier's a-posteriori output probabilities. By simulating different user selection strategies we show, that user-based active learning outperforms uncertainty based sampling methods and yields a more robust approach on different data sets. The obtained results point towards the potential of combining active learning strategies with results from the field of information visualization. © 2010 IEEE.


Pirker J.,University of Graz | Kultima A.,University of Tampere | Gutl C.,Graz University of Technology | Gutl C.,Curtin University Australia
Proceedings of the International Conference on Game Jams, Hackathons, and Game Creation Events, GJH and GC 2016 | Year: 2016

Game prototyping projects and various types of game development events teach different skills important for working in industry. This includes aspects such as advancing development and project management skills, but also improved effort estimations, first prototypes for portfolios, and strengthening networking and communication skills. Other prospects of such efforts can also be support for and the strengthening of local industry by connecting and training new talents, opening recruiting possibilities, and building a vivid and strong local developers network. In recent years, we have run different types of game prototyping projects in different settings at Graz University of Technology. These have included traditional digital 48-hour game jams, analog jams, development projects running for some months, and projects with an interdisciplinary and international setting. Each format supports different learning goals and has different potentials to bridge industry and academia. In this paper we summarize different benefits of the different formats and compare their potential to support (computer science) students in learning different aspects important for their future career and discuss general aspects related to game jams with potential or strengthening the local industry. © 2016 Copyright held by the owner/author(s). Publication rights licensed to ACM.


Brkic K.,University of Zagreb | Pinz A.,Graz University of Technology | Segvic S.,University of Zagreb | Kalafatic Z.,University of Zagreb
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2011

We introduce a novel local spatio-temporal descriptor intended to model the spatio-temporal behavior of a tracked object of interest in a general manner. The basic idea of the descriptor is the accumulation of histograms of an image function value through time. The histograms are calculated over a regular grid of patches inside the bounding box of the object and normalized to represent empirical probability distributions. The number of grid patches is fixed, so the descriptor is invariant to changes in spatial scale. Depending on the temporal complexity/details at hand, we introduce "first order STA descriptors" that describe the average distribution of a chosen image function over time, and "second order STA descriptors" that model the distribution of each histogram bin over time. We discuss entropy and χ 2 as well-suited similarity and saliency measures for our descriptors. Our experimental validation ranges from the patch- to the object-level. Our results show that STA, this simple, yet powerful novel description of local space-time appearance is well-suited to machine learning and will be useful in video-analysis, including potential applications of object detection, tracking, and background modeling. © 2011 Springer-Verlag.


Friedman D.,The Interdisciplinary Center | Leeb R.,University of Graz | Pfurtscheller G.,Graz University of Technology | Slater M.,University College London
Human-Computer Interaction | Year: 2010

We have integrated the Graz brain-computer interface (BCI) system with a highly immersive virtual reality (VR) Cave-like system. This setting allows for a new type of experience, whereby participants can control a virtual world using imagery of movement. However, current BCI systems still have many limitations. In this article we present two experiments exploring the different constraints posed by current BCI systems when used in VR. In the first experiment we let the participants make free choices during the experience and compare their BCI performance with participants using BCI without free choice; this is unlike most previous work in this area, in which participants are requested to obey cues. In the second experiment we allowed participants to control a virtual body with motor imagery. We provide both quantitative and subjective results, regarding both BCI accuracy and the nature of the subjective experience in this new type of setting.


Dey A.,University of South Australia | Jarvis G.,University of South Australia | Sandor C.,University of South Australia | Reitmayr G.,Graz University of Technology
ISMAR 2012 - 11th IEEE International Symposium on Mixed and Augmented Reality 2012, Science and Technology Papers | Year: 2012

Augmented Reality (AR) applications on mobile devices like smartphones and tablet computers have become increasingly popular. In this paper, for the first time in the AR domain, we present: (1) the influence of different handheld displays and (2) the exocentric depth perception. Unlike egocentric depth perception, exocentric depth perception has not been investigated in AR. © 2012 IEEE.


Almonasy N.,University of Pardubice | Bures F.,University of Pardubice | Nepras M.,University of Pardubice | Prichystalova H.,University of Pardubice | Grampp G.,Graz University of Technology
Dyes and Pigments | Year: 2014

Seven model donor-substituted phenyleneethynylene molecules with up to three 1,4-phenylene and two acetylenic units were synthesized by Suzuki-Miyaura and Sonogashira cross-coupling reactions and further studied by absorption and emission spectra and theoretical calculations. The π-system between the N,N-dimethylamino group and terminal acetylene was systematically elongated which allowed elucidation of the fundamental structure-property relationships. Structural factors such as molecular length and chromophore planarity proved to be crucial for the observed spectroscopic behavior. © 2014 Elsevier Ltd. All rights reserved.


Allmaier H.,Virtual Vehicle Research Center | Knauder C.,Virtual Vehicle Research Center | Salhofer S.,Virtual Vehicle Research Center | Reich F.M.,Virtual Vehicle Research Center | And 3 more authors.
International Journal of Engine Research | Year: 2016

The friction power losses of a turbo-charged heavy-duty diesel engine of the 13 litre class are investigated both by fired engine tests as well as by pressurized motoring tests. During pressurized motoring compressed air is applied to the engine intake which creates loads comparable with fired operation but without the strong and changing thermal influence of combustion. By using this combined approach the influence of the load and the thermal influence of the combustion can be studied separately for the first time. It is found that pressurized motoring yields comparable but generally a bit higher friction power losses as in fired operation. In particular, for full load operation, the agreement between the two methods is very good which supports the reasoning that for full load operation the mechanical load is the dominant factor for the friction power losses. However, for part load operation significant differences arise. Without the thermal influence from combustion, increasing the load on the engine leads to a rather linear increase in the friction power losses as is seen from pressurized motoring. This is in contrast to the fired engine tests, where the friction power losses stay almost constant over a rather large range of part loads and only increase for full load operation. It is argued that the reason for this different behaviour is the thermal impact from combustion. © Institution of Mechanical Engineers.


Franke T.,Fraunhofer Institute for Computer Graphics Research | Settgast V.,Graz University of Technology | Behr J.,Fraunhofer Institute for Computer Graphics Research | Raffin B.,French Institute for Research in Computer Science and Automation
Proceedings - Web3D 2013: 18th International Conference on 3D Web Technology | Year: 2013

In this paper, we present a specification of a RESTful based networking interface for the efficient exchange and manipulation of visual computing resources. It is designed to include web applications by using modern web-technology such as Typed Arrays and WebSockets. The specification maps internal structures and data containers to two types, Elements and Attributes, which can be queried for a description or their content. Two modes of communication are defined, one through HTTP requests, where we use HTTP operations to manipulate Elements and Attributes or request their data in a stateless fashion, the other through WebSockets to enable a push-based communication. A key idea to this interface is that we use MIME types to specify the way data is to be exchanged in. When requesting data, the user may supply a hint or type in which the data is expected to be delivered in, which enables us to write web-applications which can process already converted data that would not have been web-friendly before. To have such a mode of operation, we also present a table of extracted basic data types usable for requesting data conversion, which are derived from the Typed Array specification and shared across shader languages. Copyright © ACM 978-1-4503-2133-4/13/06 $15.00.


Landschutzer C.,Graz University of Technology
Konstruktion | Year: 2010

This paper describes the influence of the "polygonal effect" on the vibration behaviour of the chain hoist system. A simulation modell has been derived through describing all phenomenons by equations an solving them via simulation tools. These validated modelb can now be used for extensive analysis of different scenarios. Results show oscillating accalerations, the influence of deisgn parameters and the effect of changing the workload. A simple calculation for resonant chain lengths is introduced. A short description of further research - done at the institute concludes the paper.


Poletti C.,Vienna University of Technology | Rodriguez-Hortala M.,Vienna University of Technology | Hauser M.,Vienna University of Technology | Sommitsch C.,Graz University of Technology
Materials Science and Engineering A | Year: 2011

Age hardenable aluminium alloys are suitable for hot deformation at temperatures between 300 and 600°C, depending on the alloy and on the process. During thermo mechanical processes, dynamic and/or static restoration mechanisms take place. In this work, hot compression tests of hot rolled AA6082 and of a hot extruded AA6082 were carried out by means of a Gleeble® 1500 thermo-mechanical system, between 450 and 550°C and at 0.1-10s-1 of strain rate followed by fast cooling. The materials were thermo-mechanically processed before hot deformation to transform the complex initial microstructure into a fully recrystallized microstructure. Some compression tests of non recrystallized samples were carried out for comparison. All the samples were examined using electron backscatter diffraction (EBSD), followed by a determination of grain size and subgrain size distributions as well as of the local misorientation distribution. The as received samples showed a duplex microstructure consisting of elongated grains oriented in the rolling and extrusion directions, and some small recrystallized grains. The main restoration mechanism for all the materials is shown to be dynamic recovery, and the Zener-Hollomon parameter, as well as the flow stress was correlated to the subgrain size. The hot rolled material flow behaviour was sensitive to the initial microstructure, and geometric dynamic recrystallization was found. © 2010 Elsevier B.V.


Yan D.-M.,KAUST | Yan D.-M.,CAS Institute of Automation | Wallner J.,Graz University of Technology | Wonka P.,Arizona State University
IEEE Transactions on Visualization and Computer Graphics | Year: 2014

In this paper, we present a new technique to generate unbiased samples on isosurfaces. An isosurface, F(x,y,z) = c , of a function, F , is implicitly defined by trilinear interpolation of background grid points. The key idea of our approach is that of treating the isosurface within a grid cell as a graph (height) function in one of the three coordinate axis directions, restricted to where the slope is not too high, and integrating / sampling from each of these three. We use this unbiased sampling algorithm for applications in Monte Carlo integration, Poisson-disk sampling, and isosurface meshing. © 1995-2012 IEEE.


Alten K.,AIT Austrian Institute of Technology | Flesch R.,AIT Austrian Institute of Technology | Flesch R.,Graz University of Technology
Engineering Structures | Year: 2012

As part of the reconstruction of a railway bridge across the river Danube, numerical simulations were carried out during the planning stages of the project in order to investigate factors which play an important role in the radiation of structure-borne noise. The parameter studies centred around two possible construction techniques for the new bridge: an orthotropic steel deck with ballasted track, versus a composite bridge with a pre-stressed concrete deck plate and an embedded rail system. The aim was to find the optimum solution in terms of structural vibration and thus reduce resonance effects which are perceived more strongly than for tracks at-grade, as the vibration of bridge components adds to the rolling noise. Seeing as rail tracks are increasingly built in densely populated areas, this problem has become a core issue during environmental impact assessments. The results acquired from the material and structural modelling described herein were successfully implemented in the Tulln railway bridge in Lower Austria, alongside other noise-reducing measures such as sound barriers and rail grinding. © 2011 Elsevier Ltd.


Gregorc B.,Dravske Elektrarne Maribor | Predin A.,University of Maribor | Fabijan D.,Litostroj Power d.o.o. | Klasinc R.,Graz University of Technology
Strojniski Vestnik/Journal of Mechanical Engineering | Year: 2012

The purpose of this paper is to present an analysis of the impact of solid particles on the development of cavitating flow conditions around a hydrofoil. Experimental studies have been conducted in a cavitation tunnel with three different mixtures of particles and water. We used particle-like properties such as are found in river water, and with increasing mass concentration. We performed measurements of torque and the relative noise in the hydrofoil. The point in the formation of vapour phase on the hydrofoil and the pronounced frequency effect were determined by measuring the relative noise. Based on the analysis the results show that the particles increase the intensity and extent of cavitation. © 2012 Journal of Mechanical Engineering. All rights reserved.


Augsdorfer U.H.,Graz University of Technology | Dodgson N.A.,University of Cambridge | Sabin M.A.,Numerical Geometry Ltd.
Computer Aided Geometric Design | Year: 2011

Surface artifacts are features in a surface which cannot be avoided by movement of control points. They are present in B-splines, box splines and subdivision surfaces. We showed how the subdivision process can be used as a tool to analyse artifacts in surfaces defined by quadrilateral polyhedra (Sabin et al., 2005; Augsdörfer et al., 2011). In this paper we are utilising the subdivision process to develop a generic expression which can be employed to determine the magnitude of artifacts in surfaces defined by any regular triangular polyhedra. We demonstrate the method by analysing box-splines and regular regions of subdivision surfaces based on triangular meshes: Loop subdivision, Butterfly subdivision and a novel interpolating scheme with two smoothing stages. We compare our results for surfaces defined by triangular polyhedra to those for surfaces defined by quadrilateral polyhedra. © 2011 Elsevier B.V.


Augsdorfer U.H.,Graz University of Technology | Dodgson N.A.,University of Cambridge | Sabin M.A.,Numerical Geometry Ltd.
Computer Aided Geometric Design | Year: 2011

When using NURBS or subdivision surfaces as a design tool in engineering applications, designers face certain challenges. One of these is the presence of artifacts. An artifact is a feature of the surface that cannot be avoided by movement of control points by the designer. This implies that the surface contains spatial frequencies greater than one cycle per two control points. These are seen as ripples in the surface and are found in NURBS and subdivision surfaces and potentially in all surfaces specified in terms of polyhedrons of control points. Ideally, this difference between designer intent and what emerges as a surface should be eliminated. The first step to achieving this is by understanding and quantifying the artifact observed in the surface. We present methods for analysing the magnitude of artifacts in a surface defined by a quadrilateral control mesh. We use the subdivision process as a tool for analysis. Our results provide a measure of surface artifacts with respect to initial control point sampling for all B-Splines, quadrilateral box-spline surfaces and regular regions of subdivision surfaces. We use four subdivision schemes as working examples: the three box-spline subdivision schemes, Catmull-Clark (cubic B-spline), 4-3, 4-8; and Kobbelt's interpolating scheme. © 2010 Elsevier B.V.


Rapp M.,Leibniz Institute of Atmospheric Physics | Rapp M.,German Aerospace Center | Rapp M.,Ludwig Maximilians University of Munich | Plane J.M.C.,University of Leeds | And 7 more authors.
Annales Geophysicae | Year: 2012

We present in situ observations of meteoric smoke particles (MSP) obtained during three sounding rocket flights in December 2010 in the frame of the final campaign of the Norwegian-German ECOMA project (ECOMA Combining double low line Existence and Charge state Of meteoric smoke particles in the Middle Atmosphere). The flights were conducted before, at the maximum activity, and after the decline of the Geminids which is one of the major meteor showers over the year. Measurements with the ECOMA particle detector yield both profiles of naturally charged particles (Faraday cup measurement) as well as profiles of photoelectrons emitted by the MSPs due to their irradiation by photons of a xenon-flash lamp. The column density of negatively charged MSPs decreased steadily from flight to flight which is in agreement with a corresponding decrease of the sporadic meteor flux recorded during the same period. This implies that the sporadic meteors are a major source of MSPs while the additional influx due to the shower meteors apparently did not play any significant role. Surprisingly, the profiles of photoelectrons are only partly compatible with this observation: while the photoelectron current profiles obtained during the first and third flight of the campaign showed a qualitatively similar behaviour as the MSP charge density data, the profile from the second flight (i.e., at the peak of the Geminids) shows much smaller photoelectron currents. This may tentatively be interpreted as a different MSP composition (and, hence, different photoelectric properties) during this second flight, but at this stage we are not in a position to conclude that there is a cause and effect relation between the Geminids and this observation. Finally, the ECOMA particle detector used during the first and third flight employed three instead of only one xenon flash lamp where each of the three lamps used for one flight had a different window material resulting in different cut off wavelengths for these three lamp types. Taking into account these data along with simple model estimates as well as rigorous quantum chemical calculations, it is argued that constraints on MSP sizes, work function and composition can be inferred. Comparing the measured data to a simple model of the photoelectron currents, we tentatively conclude that we observed MSPs in the 0.5-3 nm size range with generally increasing particle size with decreasing altitude. Notably, this size information can be obtained because different MSP particle sizes are expected to result in different work functions which is both supported by simple classical arguments as well as quantum chemical calculations. Based on this, the MSP work function can be estimated to lie in the range from ∼4-4.6 eV. Finally, electronic structure calculations indicate that the low work function of the MSP measured by ECOMA indicates that Fe and Mg hydroxide clusters, rather than metal silicates, are the major constituents of the smoke particles. © 2012 Author(s).


Fesko K.,Graz University of Technology | Uhl M.,University of Graz | Steinreiber J.,Kompetenzzentrum Angewandte Biokatalyse | Gruber K.,University of Graz | And 2 more authors.
Angewandte Chemie - International Edition | Year: 2010

(figure presented) New donors - new products: Threonine aldolases (L-TA, D-TA) have now been found to accept donors other than glycine. In a simple asymmetric biocatalytic aldol reaction alanine, serine, and cysteine reacted with a range of simple acceptor aldehydes to yielded α-substituted serine derivatives (see scheme; PLP=pyridoxal phosphate).© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.


Markard J.,ETH Zurich | Wirth S.,Graz University of Technology | Truffer B.,Eawag - Swiss Federal Institute of Aquatic Science and Technology | Truffer B.,University Utrecht
Research Policy | Year: 2016

Legitimacy is central for both novel and established technologies to mobilize the resources necessary for growth and survival. A loss of legitimacy, in turn, can have detrimental effects for an industry. In this paper, we study the rise and fall of technology legitimacy of agricultural biogas in Germany over a period of more than 20 years (1990-2012). The field witnessed impressive growth and professionalization for many years and has become one of the key technologies in Germany's energy transition. In recent years, however, it has been confronted with major criticism, which finally resulted in a substantial cut-back of public and political support. The aim of our study is twofold. In empirical terms, we will explain the technology's loss of legitimacy despite its compliance with original policy objectives: growth and maturation. In theoretical terms, we work toward a more general framework to understand technology legitimacy and to explain the institutional dynamics of technological innovation systems. © 2015 Elsevier B.V. All rights reserved.


Schifko M.,ECS | Juttler B.,Johannes Kepler University | Kornberger B.,Graz University of Technology
Proceedings - SCCG 2010: 26th Spring Conference on Computer Graphics | Year: 2010

We present an algorithm for robust Boolean operations of triangulated solids, which is suitable for real-word industrial applications involving meshes with large numbers of triangles. In order to avoid potential robustness problems, which may be caused by (almost) degenerate triangles or by intersections of nearly co-planar triangles, we use filtered exact arithmetic, based on the libraries CGAL and GNU Multi Precision Arithmetic Library. The method consists of two major steps: First we compute the exact intersection of the meshes using a sweep plane algorithm. Second we apply mesh cleaning methods which allow us to generate output which can safely be represented using floating point numbers. The performance of the method is demonstrated by several examples which are taken from applications at ECS Magna Powertrain. Copyright © 2010 by the Association for Computing Machinery, Inc.


Hergarten S.,Graz University of Technology | Hergarten S.,University of Graz
Physical Review Letters | Year: 2012

A self-organized critical branching process based on a local interaction rule is presented. In accordance with the self-organized branching process model introduced by Zapperi, Lauritsen, and Stanley, its event-size distribution follows a power law with scaling exponent τ=32, but the new model does not require a global variable to self-organize to a critical point. The self-organized critical behavior of the model seems to be extremely robust. The model may be seen as a new paradigm for progressive mechanical failure (e.g., earthquakes or landslides) or other avalanching phenomena, and perhaps even for self-organized criticality in general.


Sasunov Y.L.,Austrian Academy of Sciences | Semenov V.S.,Saint Petersburg State University | Heyn M.F.,Graz University of Technology | Kubyshkin I.V.,Saint Petersburg State University | And 2 more authors.
Geophysical Research Letters | Year: 2012

Three solar wind reconnection exhaust events observed by the Wind satellite are compared to the analytical solution of the Riemannian decay of a current sheet due to reconnection of skewed magnetic fields. This process leads to high speed flows inside an exhaust region which is bounded not only by Alfvénic and slow mode waves but also, to a large extent, by tangential discontinuities (TDs). The TD portions of the exhaust boundary expand with distance from the X-line and therefore a long exhaust does not necessarily imply a long X-line. In some cases, portions of the exhaust show oscillations which might be connected to a Kelvin-Helmholtz instability in agreement with analytical estimates. Copyright 2012 by the American Geophysical Union.


Ambrosi D.,Polytechnic of Milan | Ateshian G.A.,Columbia University | Arruda E.M.,University of Michigan | Cowin S.C.,City University of New York | And 10 more authors.
Journal of the Mechanics and Physics of Solids | Year: 2011

The continuum mechanical treatment of biological growth and remodeling has attracted considerable attention over the past fifteen years. Many aspects of these problems are now well-understood, yet there remain areas in need of significant development from the standpoint of experiments, theory, and computation. In this perspective paper we review the state of the field and highlight open questions, challenges, and avenues for further development. © 2010 Elsevier Ltd. All rights reserved.


Doytchinov G.,Graz University of Technology
Journal of Architecture | Year: 2012

This essay is the first endeavour to sum up certain features of the Bulgarian export of architecture during the Cold War. Starting with construction firms acting in the Third World, this export was conveyed mainly by Technoexportstroy, a specialised enterprise established in 1964 by the Bulgarian Ministry of Construction, and later by the planning office Bulgarproject created in 1973. The geopolitical situation between the 1960s and 1980s was beneficial for the entrance of Bulgarian architects to post-colonial markets. They had to hold their own in competition with international architects and this paper argues that the export of architecture was based on the principles of the market economy and not on ideological influences. The number of Bulgarian architects involved can be estimated at 300-400. Alongside financial benefits, export projects gave these architects an understanding of architecture involving the work of several participants, even having to respect in some cases unpredictable interests: a situation which contrasted with socialist Bulgaria. From a range of projects, this paper discusses three examples, which together typified local economic circumstances and contributed to the welfare of the countries involved: the Olympic Sports Complex in Tunis, the bungalow projects in Sousse and the Nigerian National Theatre in Lagos. © 2012 The Journal of Architecture.


Giovannetti G.,International School for Advanced Studies | De'Medici L.,European Synchrotron Radiation Facility | Aichhorn M.,Graz University of Technology | Capone M.,International School for Advanced Studies
Physical Review B - Condensed Matter and Materials Physics | Year: 2015

We show that the insulating character of the iron selenide La2O3Fe2Se2 can be explained in terms of Mott localization in sharp contrast with the metallic behavior of FeSe and other parent compounds of iron superconductors. We demonstrate that the key ingredient that makes La2O3Fe2Se2 a Mott insulator, rather than a correlated metal dominated by the Hund's coupling, is the enhanced crystal-field splitting, accompanied by a smaller orbital-resolved kinetic energy. The strong deviation from orbital degeneracy introduced by the crystal-field splitting also pushes this material close to an orbital-selective Mott transition. We predict that either doping or uniaxial external pressure can drive the material into an orbital-selective Mott state, where only one or a few orbitals are metallized while the others remain insulating. © 2015 American Physical Society.


Stoter F.-R.,Laboratories Erlangen | Moller M.,Graz University of Technology | Edler B.,Laboratories Erlangen
MM 2015 - Proceedings of the 2015 ACM Multimedia Conference | Year: 2015

Estimating the fundamental frequency (F0) of a signal is a well studied task in audio signal processing with many applications. If the F0 varies over time, the complexity increases, and it is also more dificult to provide ground truth data for evaluation. In this paper we present a novel dataset of cello recordings addressing the lack of reference annotations for musical instruments. Besides audio data, we include sensor recordings capturing the finger position on the fingerboard which is converted into an instantaneous frequency estimate. In speech processing, the electroglottograph (EGG) is able to capture the excitation signal of the vocal tract, which is then used to generate a reference instantaneous F0. Inspired by this approach, we included high speed video camera recordings to extract the excitation signal originating from the moving string. The derived data can be used to analyze vibratos|a very commonly used playing style. The dataset is released under a Creative Commons license. © 2015 ACM.


Rozantsev A.,Ecole Polytechnique Federale de Lausanne | Lepetit V.,Ecole Polytechnique Federale de Lausanne | Lepetit V.,Graz University of Technology | Fua P.,Ecole Polytechnique Federale de Lausanne
Proceedings of the IEEE Computer Society Conference on Computer Vision and Pattern Recognition | Year: 2015

We propose an approach to detect flying objects such as UAVs and aircrafts when they occupy a small portion of the field of view, possibly moving against complex backgrounds, and are filmed by a camera that itself moves. Solving such a difficult problem requires combining both appearance and motion cues. To this end we propose a regression-based approach to motion stabilization of local image patches that allows us to achieve effective classification on spatio-temporal image cubes and outperform state-of-the-art techniques. As the problem is relatively new, we collected two challenging datasets for UAVs and Aircrafts, which can be used as benchmarks for flying objects detection and vision-guided collision avoidance. © 2015 IEEE.


Ross S.,Carnegie Mellon University | Melik-Barkhudarov N.,Carnegie Mellon University | Shankar K.S.,Carnegie Mellon University | Wendel A.,Graz University of Technology | And 3 more authors.
Proceedings - IEEE International Conference on Robotics and Automation | Year: 2013

Autonomous navigation for large Unmanned Aerial Vehicles (UAVs) is fairly straight-forward, as expensive sensors and monitoring devices can be employed. In contrast, obstacle avoidance remains a challenging task for Micro Aerial Vehicles (MAVs) which operate at low altitude in cluttered environments. Unlike large vehicles, MAVs can only carry very light sensors, such as cameras, making autonomous navigation through obstacles much more challenging. In this paper, we describe a system that navigates a small quadrotor helicopter autonomously at low altitude through natural forest environments. Using only a single cheap camera to perceive the environment, we are able to maintain a constant velocity of up to 1.5m/s. Given a small set of human pilot demonstrations, we use recent state-of-the-art imitation learning techniques to train a controller that can avoid trees by adapting the MAVs heading. We demonstrate the performance of our system in a more controlled environment indoors, and in real natural forest environments outdoors. © 2013 IEEE.


Zellnitz S.,Research Center Pharmaceutical Engineering GmbH | Schroettner H.,Graz University of Technology | Urbanetz N.A.,Research Center Pharmaceutical Engineering GmbH
Powder Technology | Year: 2014

The relationship between surface coverage and in vitro respirable fraction-often referred to as fine particle fraction (FPF)-of dry powder inhaler (DPI) formulations for the therapy of asthma was investigated using an artificial lung, the next generation impactor (NGI). Therefore mixtures with 100%, 50% and 25% calculated surface coverage of physically and chemically modified glass beads as model carrier and spray dried salbutamol sulfate as active pharmaceutical ingredient (API) have been prepared. In any of these cases the actual surface coverage was lower than the calculated surface coverage as a certain amount of API particles adheres to the mixing container wall instead of the glass bead surface. Moreover, API particles detach from the glass bead surface during capsule filling and transport resulting in even lower true surface coverage at the moment when the NGI experiments are performed. When investigating the FPF this true surface coverage has to be taken into account. The FPF increased more or less linearly with increasing surface coverage of the surface modified glass beads but the slopes of the lines are different depending of the carriers used. This can be attributed to the distribution of active sites on the glass bead surface that is individually depending on the surface modification applied and the processing time. However the influence of surface coverage on FPF is also influenced by the choice of the carrier particles. Compared to untreated glass beads physically modified glass beads show increased FPFs whereas chemically modified glass beads show lower FPFs. © 2014 Elsevier B.V.


Karpenkov O.,Graz University of Technology | Sossinsky A.B.,Russian Academy of Sciences
Russian Journal of Mathematical Physics | Year: 2011

We introduce and begin the study of new knot energies defined on knot diagrams. Physically, they model the internal energy of thin metallic solid tori squeezed between two parallel planes. Thus the knots considered can perform the second and third Reidemeister moves, but not the first one. The energy functionals considered are the sum of two terms, the uniformization term (which tends to make the curvature of the knot uniform) and the resistance term (which, in particular, forbids crossing changes). We define an infinite family of uniformization functionals, depending on an arbitrary smooth function f and study the simplest nontrivial case f(x) = x2, obtaining neat normal forms (corresponding to minima of the functional) by making use of the Gauss representation of immersed curves, of the phase space of the pendulum, and of elliptic functions. © 2011 Pleiades Publishing, Ltd.


Gebhart M.,Graz University of Technology
Proceedings of the 13th International Conference on Telecommunications, ConTEL 2015 | Year: 2015

Unlike in conventional Wireleb Communication, Contactleb Communication technologies like Near Field Communication (NFC), Proximity Card systems or RFID Labels operated at 13.56 MHz are very much impacted by signal distortion caused by de-Tuning of resonant loop antennas. In fact, these effects define the near-field communication channel over just a few centimeters operating distance. To ensure interoperability, modulation signal specifications at the air interface provided in base standards must be strictly maintained. Consequently, accurate measurement methods are important and it is ebential for system design to meet the specifications. This paper shows a method to consider reader modulation at the air interface of the contactleb coupling channel. We apply this method on two scenarios: On the Proximity Coupling Device (PCD) test environment for Card testing, and on a real reader coupled to NFC Forum Listener 1. © 2015 IEEE.


Gebhart M.,Graz University of Technology
Proceedings of the 13th International Conference on Telecommunications, ConTEL 2015 | Year: 2015

Contactleb Payment incorporates the Proximity card specification for the physical-layer of the air interface. The physics is based on the coupling of resonant loop antenna circuits in the inductive near-field. Two main effects determine the near-field communication channel in the 13.56 MHz ISM frequency band: A strong decrease of H-field with increasing distance between reader and card, and a shift of resonance, or in fact a change of impedance. Understanding this impact on the reader antenna impedance as a function of coupling with the card, which also incorporates a certain impedance, is key to understanding all specified aspects of the physical-layer at the air interface. We investigate this impedance for the EMVCo test environment under operating conditions, with direct measurement and using analytical equations. We provide equivalent circuit element values for the specified test devices and also impedance values for positions in the operating volume. © 2015 IEEE.


Karner S.,Graz University of Technology | Maier M.,Research Center Pharmaceutical Engineering GmbH | Littringer E.,Research Center Pharmaceutical Engineering GmbH | Urbanetz N.A.,Research Center Pharmaceutical Engineering GmbH
Powder Technology | Year: 2014

For active pharmaceutical ingredients (APIs) delivered to the lung it is of main importance that they reach the deeper lung, in order to cause the intended therapeutic effect. To obtain inhalable powders that on the one hand are small enough to travel along the tiny airways finally reaching their target site and on the other hand show sufficient flowability, so-called adhesive mixtures are used. They consist of API particles in the size range of 0.5. μm-5. μm and carrier particles in the size range of 50. μm-200. μm, that, due to the size of the carrier, exhibit adequate flowability. However, when administered to the patient, the API has to separate from the carrier surface in order to be able to penetrate the deep lung. The performance of dry powder inhalers (DPIs) and adhesive mixtures is mainly governed by interparticle forces like Van der Waals and triboelectric forces. Carrier surface roughness modification is a new method to alter the contact area and thus the Van der Waals forces between API and carrier. Unfortunately the tribo-charging during handling, especially during the generation of the adhesive mixtures in a tumble blender, is strongly influenced by particle characteristics like particle surface roughness. Thus the mixing quality and stability and thereby the usability of the powder mixture might be additionally influenced by tribo-charging. Therefore the aim of the present work is to investigate whether tribo-charging during the mixing process is influenced by the carrier particle surface roughness. Further the influence of tribo-charging on mixing homogeneity is assessed. Net charge measurements are performed using a Faraday cup. As model API and carrier salbutamol sulfate and spray dried mannitol are used respectively. It is shown that the carrier particle characteristics impact tribo-charging of the pure carriers in a tumble blender. This influence is not observed for the adhesive mixtures of carrier and API. Nevertheless the homogeneity of the adhesive mixtures is still influenced by the charging of the carriers. © 2014.


Lienhart W.-D.,University of Graz | Gudipati V.,University of Graz | Uhl M.K.,University of Graz | Binter A.,University of Graz | And 5 more authors.
FEBS Journal | Year: 2014

Human NAD(P)H:quinone oxidoreductase 1 (NQO1) is essential for the antioxidant defense system, stabilization of tumor suppressors (e.g. p53, p33, and p73), and activation of quinone-based chemotherapeutics. Overexpression of NQO1 in many solid tumors, coupled with its ability to convert quinone-based chemotherapeutics into potent cytotoxic compounds, have made it a very attractive target for anticancer drugs. A naturally occurring single-nucleotide polymorphism (C609T) leading to an amino acid exchange (P187S) has been implicated in the development of various cancers and poor survival rates following anthracyclin-based adjuvant chemotherapy. Despite its importance for cancer prediction and therapy, the exact molecular basis for the loss of function in NQO1 P187S is currently unknown. Therefore, we solved the crystal structure of NQO1 P187S. Surprisingly, this structure is almost identical to NQO1. Employing a combination of NMR spectroscopy and limited proteolysis experiments, we demonstrated that the single amino acid exchange destabilized interactions between the core and C-terminus, leading to depopulation of the native structure in solution. This collapse of the native structure diminished cofactor affinity and led to a less competent FAD-binding pocket, thus severely compromising the catalytic capacity of the variant protein. Hence, our findings provide a rationale for the loss of function in NQO1 P187S with a frequently occurring single-nucleotide polymorphism. © 2014 The Authors.


Daemen J.,STMicroelectronics | Rijmen V.,Catholic University of Leuven | Rijmen V.,Graz University of Technology
IET Information Security | Year: 2010

The authors present three security claims for iterated message authentication codes (MAC functions). Next, they propose ALRED, a construction method for MAC functions based on a block cipher that has provable security in the absence of internal collisions. They apply this construction to advanced encryption standard (AES) resulting in two MAC functions: ALPHA-MAC and PELICAN. The authors provide a model for describing different types of internal collisions in ALRED and provide evidence that the security claims they propose are usable for MAC functions that use the ALRED construction. Finally, they provide a motivation for the security claims that accompany PELICAN. © 2010 The Institution of Engineering and Technology.


Kieffer D.S.,Graz University of Technology | Zhang Z.,Tongji University | Hu X.,Shanghai Institute of Technology
North American Tunneling - 2014 Proceedings, NAT 2014 | Year: 2014

The current tendency toward ever-larger TBMs is accompanied by a higher probability of significant mixed-face conditions. The unprecedented 17.45 m diameter earth pressure balance TBM for the Alaskan Way Viaduct Replacement Program (AWVRP) is a contemporary example. The TBM is being driven through complexly layered glacial sands and clays, wherein several alternating soil units may comprise the tunnel face. Analyzing the required TBM face pressure under such conditions is a non-trivial task and has been facilitated by the recently developed multilayer wedge method (MWM) (Hu et al., 2012). This paper introduces key aspects of the MWM and its application at the AWVRP. Results obtained with the MWM are compared to classical methods for predicting required face pressure.


Werner M.,Graz University of Technology | Greif H.,Klagenfurt University
TripleC | Year: 2010

In this paper, findings of a study on the perception and policing of information-technology (ICT) related operational risks in banking are presented, with a view on identifying some part of the role that these technologies, and the specific organisational settings in which they are embedded, may have played in the making of the 2007+ financial crisis. The study's findings concern, firstly, biases in risk perception that turn a blind eye towards certain operational risks; secondly, competing, qualitative vs. quantitative norms and methods of risk analysis and management and their significance for the governance of financial institutions; and thirdly, the role of ICTs as organisational technologies that work both as sources and as remedies of operational risks. The use of ICTs in financial institutions, it is concluded, while not being fully acknowledged in its organisational role, caters to the calculative rationality to which the analysis, management and governance of operational and other risks are increasingly subjected. Presuming that all kinds of risk can be made calculable and computable, this calculative rationality either misses out or obscures one important risk category: low frequency/ high magnitude risks, which tend to cross the boundary between calculable risk and genuine uncertainty of knowledge.


Kwabi D.G.,Massachusetts Institute of Technology | Ortiz-Vitoriano N.,Massachusetts Institute of Technology | Freunberger S.A.,Graz University of Technology | Chen Y.,University of St. Andrews | And 3 more authors.
MRS Bulletin | Year: 2014

Lithium-air batteries have received extraordinary attention recently owing to their theoretical gravimetric energies being considerably higher than those of Li-ion batteries. There are, however, significant challenges to practical implementation, including low energy efficiency, cycle life, and power capability. These are due primarily to the lack of fundamental understanding of oxygen reduction and evolution reaction kinetics and parasitic reactions between oxygen redox intermediate species and nominally inactive battery components such as carbon in the oxygen electrode and electrolytes. In this article, we discuss recent advances in the mechanistic understanding of oxygen redox reactions in nonaqueous electrolytes and the search for electrolytes and electrode materials that are chemically stable in the oxygen electrode. In addition, methods to protect lithium metal against corrosion by water and dendrite formation in aqueous lithium-air batteries are discussed. Further materials innovations lie at the heart of research and development efforts that are needed to enable the development of lithium-oxygen batteries with enhanced round-trip efficiency and cycle life. © 2014 Materials Research Society.


Ortenzi L.,CNR Institute of Neuroscience | Ortenzi L.,Max Planck Institute for Solid State Research | Gretarsson H.,Max Planck Institute for Solid State Research | Gretarsson H.,University of Toronto | And 10 more authors.
Physical Review Letters | Year: 2015

We report a combination of Fe Kβ x-ray emission spectroscopy and density functional reduced Stoner theory calculations to investigate the correlation between structural and magnetic degrees of freedom in CaFe2(As1-xPx)2. The puzzling temperature behavior of the local moment found in rare earth-doped CaFe2As2 [H. Gretarsson et al., Phys. Rev. Lett. 110, 047003 (2013)] is also observed in CaFe2(As1-xPx)2. We explain this phenomenon based on first-principles calculations with scaled magnetic interaction. One scaling parameter is sufficient to describe quantitatively the magnetic moments in both CaFe2(As1-xPx)2 (x=0.055) and Ca0.78La0.22Fe2As2 at all temperatures. The anomalous growth of the local moments with increasing temperature can be understood from the observed large thermal expansion of the c-axis lattice parameter combined with strong magnetoelastic coupling. These effects originate from the strong tendency to form As-As dimers across the Ca layer in the CaFe2As2 family of materials. Our results emphasize the dual local-itinerant character of magnetism in Fe pnictides. © 2015 American Physical Society.


Koch M.,Norwegian University of Science and Technology | Krammer G.,Norwegian University of Science and Technology | Krammer G.,Graz University of Technology
Powder Technology | Year: 2016

Cleanable fabric filters such as bag filters are widely used in industrial processes to remove large quantities of solid particles from gas streams. Intrinsically, such a filtration process is as non-uniform as it is semi-continuous; that is, filter cake build-up processes are successively followed by a short-duration cleaning step. Moreover, heterogeneous flow conditions and, thus, concentrations of particles entering the filter housing and flowing toward the filter contribute to rather non-uniform filter conditions. Since cleaning is not necessarily performed in a homogeneous manner, and patches of cake might remain on the filter fabric, the subsequent filtration is also non-uniform. Finally, the filter medium itself is largely heterogeneous certainly on micro-, but often also on a macro-scale.The influence of a heterogeneous dust concentration as a common filter non-uniformity is investigated on filter performance, i.e., pressure drop increase as a measure for filter cycle cleaning frequency being a precursor for filter life-time, dust emissions and operating costs.Laboratory tests were performed whereby the pressure increase curves are recorded at basically constant gas flow. As a baseline the entire filter area was exposed to a homogeneous dust concentration. Comparatively the filtration area was split into two zones where cake formation occurred under a high and a low particle concentration mimicking a distinctive heterogeneous dust concentration situation. The transient pressure increase profiles of both, the homogeneous and heterogeneous cake formation situation, were compared with each other.The apparent filter cake resistance was slightly higher under homogeneous dust concentration conditions, i.e., the pressure drop increased faster compared with the situation of a heterogeneous dust concentration. These results suggest that, in practical terms, a filter exposed to non-uniform dust concentrations exhibits a better overall performance. Consequently aiming for a most uniform dust concentration is to no avail, though often intended in industrial operation. © 2016 Elsevier B.V.


Zheng F.,University of North Carolina at Chapel Hill | Schmalstieg D.,Graz University of Technology | Welch G.,University of Central Florida
ISMAR 2014 - IEEE International Symposium on Mixed and Augmented Reality - Science and Technology 2014, Proceedings | Year: 2014

In Augmented Reality (AR), visible misregistration can be caused by many inherent error sources, such as errors in tracking, calibration, and modeling. In this paper we present a novel pixel-wise closed-loop registration framework that can automatically detect and correct registration errors using a reference model comprised of the real scene model and the desired virtual augmentations. Registration errors are corrected in both global world space via camera pose refinement, and local screen space via pixel-wise corrections, resulting in spatially accurate and visually coherent registration. Specifically we present a registration-enforcing model-based tracking approach that weights important image regions while refining the camera pose estimates (from any conventional tracking method) to achieve better registration, even in the case of modeling errors. To deal with remaining errors, which can be rigid or non-rigid, we compute the optical flow between the camera image and the real model image rendered with the refined pose, enabling direct screen-space pixel-wise corrections to misregistration. The estimated flow field can be applied to improve registration in two distinct ways: (1) forward warping of modeled on-real-object-surface augmentations (e.g., object re-texturing) into the camera image, leading to surface details that are not present in the virtual object; and (2) backward warping of the camera image into the real scene model, preserving the full use of the dense geometry buffer (depth in particular) provided by the combined real-virtual model for registration, leading to pixel accurate real-virtual occlusion. We discuss the trade-offs between, and different use cases of, forward and backward warping with model-based tracking in terms of specific properties for registration. We demonstrate the efficacy of our approach with both simulated and real data. © 2014 IEEE.


Spanova M.,University of Graz | Zweytick D.,Austrian Academy of Sciences | Lohner K.,Austrian Academy of Sciences | Klug L.,University of Graz | And 3 more authors.
Biochimica et Biophysica Acta - Molecular and Cell Biology of Lipids | Year: 2012

In a previous study (Spanova et al., 2010, J. Biol. Chem., 285, 6127-6133) we demonstrated that squalene, an intermediate of sterol biosynthesis, accumulates in yeast strains bearing a deletion of the HEM1 gene. In such strains, the vast majority of squalene is stored in lipid particles/droplets together with triacylglycerols and steryl esters. In mutants lacking the ability to form lipid particles, however, substantial amounts of squalene accumulate in organelle membranes. In the present study, we investigated the effect of squalene on biophysical properties of lipid particles and biological membranes and compared these results to artificial membranes. Our experiments showed that squalene together with triacylglycerols forms the fluid core of lipid particles surrounded by only a few steryl ester shells which transform into a fluid phase below growth temperature. In the hem1Δ deletion mutant a slight disordering effect on steryl esters was observed indicated by loss of the high temperature transition. Also in biological membranes from the hem1Δ mutant strain the effect of squalene per se is difficult to pinpoint because multiple effects such as levels of sterols and unsaturated fatty acids contribute to physical membrane properties. Fluorescence spectroscopic studies using endoplasmic reticulum, plasma membrane and artificial membranes revealed that it is not the absolute squalene level in membranes but rather the squalene to sterol ratio which mainly affects membrane fluidity/rigidity. In a fluid membrane environment squalene induces rigidity of the membrane, whereas in rigid membranes there is almost no additive effect of squalene. In summary, our results demonstrate that squalene (i) can be well accommodated in yeast lipid particles and organelle membranes without causing deleterious effects; and (ii) although not being a typical membrane lipid may be regarded as a mild modulator of biophysical membrane properties. © 2012 Elsevier B.V. All rights reserved.


Pottmann H.,Vienna University of Technology | Huang Q.,Stanford University | Deng B.,Vienna University of Technology | Schiftner A.,Evolute GmbH | And 3 more authors.
ACM Transactions on Graphics | Year: 2010

Geodesic curves in surfaces are not only minimizers of distance, but they are also the curves of zero geodesic (sideways) curvature. It turns out that this property makes patterns of geodesics the basic geometric entity when dealing with the cladding of a freeform surface with wooden panels which do not bend sideways. Likewise a geodesic is the favored shape of timber support elements in freeform architecture, for reasons of manufacturing and statics. Both problem areas are fundamental in freeform architecture, but so far only experimental solutions have been available. This paper provides a systematic treatment and shows how to design geodesic patterns in different ways: The evolution of geodesic curves is good for local studies and simple patterns; the level set formulation can deal with the global layout of multiple patterns of geodesics; finally geodesic vector fields allow us to interactively model geodesic patterns and perform surface segmentation into panelizable parts. © 2010 ACM.


Wang J.,KAUST | Jiang C.,KAUST | Wallner J.,Graz University of Technology | Pottmann H.,KAUST | Pottmann H.,Vienna University of Technology
Computer Graphics Forum | Year: 2013

Two-parameter families of straight lines (line congruences) are implicitly present in graphics and geometry processing in several important ways including lighting and shape analysis. In this paper we make them accessible to optimization and geometric computing, by introducing a general discrete version of congruences based on piecewise-linear correspondences between triangle meshes. Our applications of congruences are based on the extraction of a so-called torsion-free support structure, which is a procedure analogous to remeshing a surface along its principal curvature lines. A particular application of such structures are freeform shading and lighting systems for architecture. We combine interactive design of such systems with global optimization in order to satisfy geometric constraints. In this way we explore a new area where architecture can greatly benefit from graphics. © 2013 The Author(s) Computer Graphics Forum © 2013 The Eurographics Association and John Wiley & Sons Ltd.


Ambrosch-Draxl C.,University of Leoben | Hofmann O.T.,University of Graz | Hofmann O.T.,Graz University of Technology | Hsu J.W.P.,Sandia National Laboratories
MRS Bulletin | Year: 2010

Organic-based interfaces can possess a range of surpising electronic properties that are of intense interest from both the basic science and the applied research points of view. In this issue of MRS Bulletin, we provided state-of-the-art overviews of selected topics involving three complementary aspects of the electronic properties of organicbased interfaces: the nascent electronics technologies that would gain from improved understanding and control of such interfaces: the novel properties that organic-based interfaces may possess: and the experimental and theoretical challenges afforded by such studies.


Mangani L.,Lucerne University of Applied Sciences | Buchmayr M.,Andritz AG | Buchmayr M.,Graz University of Technology | Darwish M.,American University of Beirut
Numerical Heat Transfer, Part B: Fundamentals | Year: 2014

In this article, the fully coupled block algorithm for the solution of three-dimensional incompressible turbulent flows presented in a companion article [1] is extended for use with multiple reference frames and multiple mesh blocks. The implicit block coupling is applied to the extra rotational terms, and to the multiblock interfaces. Furthermore, implementation details on the linearization of cyclic and other boundary conditions are detailed. These modifications allow the coupled solver to retain its improved performance and robustness in addition to mesh size scalability while solving turbomachinery-type applications. The performance and mesh size scalability of the coupled solver is compared to that of a segregated pressure based solver [2] using three industrial-size test cases. © 2014 Taylor and Francis Group, LLC.


Musliu N.,Vienna University of Technology | Slany W.,Graz University of Technology | Gartner J.,XIMES GmbH
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2013

Generation of test cases for end-user programmers is crucial to assure the correctness of their code. In this paper we investigate the automatic generation of test cases for programs that are written in Visual Basic for Applications and are used in MS Excel. We implement a metaheuristic search method to generate tests that achieve a satisfactory statement and branch coverage. Furthermore, in our methodology the code coverage is visualized. The generated test cases and the visualization enable end users to better understand the behavior of the programs and increase the probability of detecting errors when the code is changed at a later time. © 2013 Springer-Verlag.


Donoser M.,Graz University of Technology | Riemenschneider H.,ETH Zurich
Proceedings of the IEEE International Conference on Computer Vision | Year: 2013

This paper introduces a novel method for categorical image labeling, where each pixel is uniquely assigned to one of a set of unordered, discrete labels. Starting from provided label-depending pixel likelihoods we (a) exploit a segment hierarchy as spatial support to define powerful priors and (b) introduce an efficient and effective inference method, that can be implemented in a few lines of code. Experiments show that competitive labeling accuracy compared to related discrete, continuous, segmentation and filtering approaches is achieved. © 2013 IEEE.


Zubiaga A.,Spanish University for Distance Education (UNED) | Korner C.,Graz University of Technology | Strohmaier M.,University of Graz
HT 2011 - Proceedings of the 22nd ACM Conference on Hypertext and Hypermedia | Year: 2011

Recent research has shown that different tagging motivation and user behavior can effect the overall usefulness of social tagging systems for certain tasks. In this paper, we provide further evidence for this observation by demonstrating that tagging data obtained from certain types of users - so-called Categorizers - outperforms data from other users on a social classification task. We show that segmenting users based on their tagging behavior has significant impact on the performance of automated classification of tagged data by using (i) tagging data from two different social tagging systems, (ii) a Support Vector Machine as a classification mechanism and (iii) existing classification systems such as the Library of Congress Classification System as ground truth. Our results are relevant for scientists studying pragmatics and semantics of social tagging systems as well as for engineers interested in inuencing emerging properties of deployed social tagging systems. © 2011 ACM.


Karner S.,Graz University of Technology | Littringer E.M.,Research Center Pharmaceutical Engineering GmbH | Urbanetz N.A.,Research Center Pharmaceutical Engineering GmbH
Powder Technology | Year: 2014

For active pharmaceutical ingredients (API) delivered to the lung it is of main importance that they reach the deeper lung, in order to cause the intended therapeutic effect. To ensure lung deposition and uniform dosage, adhesive mixtures of API particles in the size range of 0.5. μm-5. μm and inert carrier particles in the size range of 50. μm-200. μm are used in dry powder inhalers (DPI). The performance of DPIs and adhesive mixtures are mainly governed by interparticle forces like Van der Waals and tribo-electric forces between the active and the carrier as well as between the particles of the adhesive mixture and between adhesive mixture particles and inhaler wall. The arising tribo-charge on the mixtures during handling is influenced by various particle and material characteristics. For adequate inhaler performance especially the charge arising on the powder during the release from the inhaler is of interest. Therefore the aim of this work is to investigate how tribo-charging during aerosolization and release of the powder from a common DPI (Novolizer®) is affected by the carrier particle characteristics of surface roughness and shape and how the accumulated charge further influences the inhaler performance. Tribo-charge measurement of the pure carriers and the adhesive mixtures was performed using an open-end faraday cup. As model API and carrier salbutamol sulphate and spray dried mannitol were used. It was possible to show that tribo-charging during aerosolization is significantly influenced by the above mentioned particle characteristics. Further it was shown that this charge has also significant effects on the important performance properties of the DPI like fine particle dose and fine particle fraction. © 2014 Elsevier B.V.


Stevanovic A.,Florida Atlantic University | Gundogan F.,Graz University of Technology
19th Intelligent Transport Systems World Congress, ITS 2012 | Year: 2012

When traffic microsimulation models are used to evaluate various traffic alternatives, especially ITS applications, emphasis is often put on algorithmic procedures to successfully fit simulation outputs with the field performance measures. Most of such procedures lack an expertise-based approach to assess which simulation parameters, and to what extent, should be modified to get a trustworthy simulation model. This study suggests a slightly different approach where iterative adjustment of simulation parameters is combined with manual calibration based on modeller's expertise. The process introduces frequent reasonability checks to ensure that modelled traffic conditions do not contradict logical and reasonable traffic operations. Once the modelled results become generally acceptable an iterative procedure (e.g. Genetic Algorithm) can be applied to fine-tune simulation parameters, especially those related to driver behaviour. Results of the case study presented in the paper showed that microsimualtion models can be adjusted to verifiably resemble field conditions.


Mowlaee P.,Graz University of Technology | Saeidi R.,Radboud University Nijmegen
ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings | Year: 2013

In this paper, we study the impact of exploiting the spectral phase information to further improve the speech quality of the single-channel speech enhancement algorithms. In particular, we focus on the two required steps in a typical single-channel speech enhancement system, namely: parameter estimation solved by a minimum mean square error (MMSE) estimator of the speech spectral amplitude, followed by signal reconstruction stage, where the observed noisy phase is often used. For the parameter estimation stage, in contrast to conventional Wiener filter, a new MMSE estimator is derived which takes into account the clean phase information as a prior information. In our experiments, we show that by including the phase information in the two steps, it is possible to improve the perceived signal quality of the enhanced signal significantly with respect to the methods that do not employ the phase information. © 2013 IEEE.


Spreitzer R.,Graz University of Technology | Gerard B.,Directorate General of Armaments
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2014

Side-channel attacks are usually performed by employing the "divide-and-conquer" approach, meaning that leaking information is collected in a divide step, and later on exploited in the conquer step. The idea is to extract as much information as possible during the divide step, and to exploit the gathered information as efficiently as possible within the conquer step. Focusing on both of these steps, we discuss potential enhancements of Bernstein's cache-timing attack against the Advanced Encryption Standard (AES). Concerning the divide part, we analyze the impact of attacking different key-chunk sizes, aiming at the extraction of more information from the overall encryption time. Furthermore, we analyze the most recent improvement of time-driven cache attacks, presented by Aly and ElGayyar, according to its applicability on ARM Cortex-A platforms. For the conquer part, we employ the optimal key-enumeration algorithm as proposed by Veyrat-Charvillon et al. to significantly reduce the complexity of the exhaustive key-search phase compared to the currently employed threshold-based approach. This in turn leads to more practical attacks. Additionally, we provide extensive experimental results of the proposed enhancements on two Android-based smartphones, namely a Google Nexus S and a Samsung Galaxy SII. © 2014 IFIP International Federation for Information Processing.


Aichernig B.K.,Graz University of Technology
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2013

In this paper we give an overview of our work on combining model-based testing and mutation testing. Model-based testing is a black-box testing technique that avoids the labour of manually writing hundreds of test cases, but instead advocates the capturing of the expected behaviour in a model of the system-under-test. The test cases are automatically generated from this model. The technique is receiving growing interest in the embedded-systems domain, where models are the rule rather than the exception. Mutation testing is a technique for assessing and improving a test suite. A number of faulty versions of a program-under-test are produced by injecting bugs into its source code. These faulty programs are called mutants. A tester analyses if his test suite can "kill" all mutants. We say that a test kills a mutant if it is able to distinguish it from the original. The tester improves his test suite until all faulty mutants get killed. In model-based mutation testing, we combine the central ideas of model-based testing and mutation testing: we inject bugs in a model and generate a test suite that will kill these bugs. In this paper, we discuss its scientific foundations and tools. The foundations include semantics and conformance relations; the supporting tools involve model checkers, constraint solvers and SMT solvers. © 2013 Springer-Verlag.


Woschitz H.,Graz University of Technology
SHMII-5 2011 - 5th International Conference on Structural Health Monitoring of Intelligent Infrastructure | Year: 2011

Railway tracks in alpine regions consist of many curves with small radii of often less than 300 m. There, the elastic pads that are mounted in between the rail and the sleepers are affected by enormous stresses. In the narrow curves, the elastic pads must be replaced every few years which is time consuming and cost intensive. If the deterioration of the elastic pads is not detected in time, the sleepers will be damaged too, and as a consequence the train traffic needs to be shut down during its replacement. Mainly, horizontal forces are assumed to cause the accelerated deterioration of the elastic pads. Consequently, more durable materials are under development currently. However, the forces that are generated by a train passage and subsequently the strain inside the elastic pad are insufficiently known. In this paper, the development of a fiber-optic rail-strain-pad (RASP) is described. Several fiber Bragg grating (FBG) sensors are embedded into the elastic pad during the production process. Challenges in the development were the very small dimensions of the structure (size of the pad: 150 × 160 × 7 mm3) and the large strain values of several 1 000 με that are induced by loading the pad. Draw-tower gratings were used, as this sensor type was the only one to withstand the large strains of more than 30 000 με. Several RASP prototypes were developed and tested. Experimental results are shown in order to demonstrate the capabilities of the system to measure large strains. In future, the RASP will be used for weigh-in-motion issues.


Breitwieser C.,Graz University of Technology
Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference | Year: 2011

Steady-state somatosensory evoked potentials (SSSEPs) have been elicited using vibro-tactile stimulation on two fingers of the right hand. Fourteen healthy subjects participated in this study. A screening session, stimulating each participant's thumb, was conducted to determine individual optimal resonance-like frequencies. After this screening session, two stimulation frequencies per subject were selected. Stimulation was then applied simultaneously on the participant's thumbs and middle finger. It was investigated whether it is possible to classify SSSEP changes based on an attention modulation task to determine possible BCI applications. A cue indicated the participants to shift their attention to either the thumb or the middle finger. Offline classification with a lock-in analyzer system (LAS) and a linear discriminant analysis (LDA) classifier was performed. One bipolar channel and no further optimization methods were used. All participants except one reached classification results above chance level classifying a reference period without focused attention against focused attention either to the thumb or the middle finger. Only two subjects reached accuracies above chance, classifying focused attention to the thumb vs. attention to the middle finger.


Pustka D.,TU Munich | Huber M.,TU Munich | Waechter C.,TU Munich | Echtler F.,TU Munich | And 4 more authors.
IEEE Pervasive Computing | Year: 2011

The ubiquitous tracking (Ubitrack) approach uses spatial relationship graphs and patterns to support a distributed software architecture for augmented reality (AR) systems in which clients can produce, transform, transmit, and consume tracking data. © 2006 IEEE.


Cerwenka P.,Graz University of Technology
Traffic Engineering and Control | Year: 2012

Numerous professional articles on (economic) external effects also concern transport. In doing so they either presuppose knowledge of the concept or refer to relevant literature or themselves provide a definition which as a rule may be acceptable, but in specific cases leaves room for some scope. In what follows we shall try to remove such lack of clarity by more precision. For the example of road traffic congestion we shall clarify its economic status. Finally the method of dealing with such status will be examined in two actual cases (the European Union and Switzerland).


Stefl M.,J. Heyrovsky Institute of Physical Chemistry | Sachl R.,J. Heyrovsky Institute of Physical Chemistry | Olzynska A.,J. Heyrovsky Institute of Physical Chemistry | Amaro M.,J. Heyrovsky Institute of Physical Chemistry | And 6 more authors.
Biochimica et Biophysica Acta - Biomembranes | Year: 2014

Biological membranes are under significant oxidative stress caused by reactive oxygen species mostly originating during cellular respiration. Double bonds of the unsaturated lipids are most prone to oxidation, which might lead to shortening of the oxidized chain and inserting of terminal either aldehyde or carboxylic group. Structural rearrangement of oxidized lipids, addressed already, is mainly associated with looping back of the hydrophilic terminal group. This contribution utilizing dual-focus fluorescence correlation spectroscopy and electron paramagnetic resonance as well as atomistic molecular dynamics simulations focuses on the overall changes of the membrane structural and dynamical properties once it becomes oxidized. Particularly, attention is paid to cholesterol rearrangement in the oxidized membrane revealing its preferable interaction with carbonyls of the oxidized chains. In this view cholesterol seems to have a tendency to repair, rather than condense, the bilayer. © 2014 Elsevier B.V.


Donner R.,Medical University of Vienna | Bischof H.,Graz University of Technology
Proceedings - International Symposium on Biomedical Imaging | Year: 2013

We propose an approach which allows to localize anatomical landmarks in radiological datasets given only a single manual annotation and set of un-annotated example images. Using top-down image patch regression to obtain potential landmark candidates in the set of training images, a model of the anatomical structure is incrementally enlarged, starting from the single, annotated image, until it encompasses the entire training set. The obtained model then allows to perform highly accurate anatomical structure localization on test data. We report preliminary results on a set of 2D radio-graphs, with a median / mean localization residual of 0.92mm/ 1.30 mm. The approach yields very promising localization results, suggesting that is possible to eliminate the tedious manual annotation process still required by state of the art localization approaches. © 2013 IEEE.


Durkee S.R.,University of Warwick | Muetze A.,Graz University of Technology
IET Conference Publications | Year: 2010

The large number of rotating parts in a conventional helicopter powertrain motivates the study of an electric alternative. The feasibility of such an electrically driven helicopter is not straightforward; however it is promising provided a good understanding of both the helicopter flying requirements and the possibilities given by modern custom-designed drive systems are brought together. As with electric vehicles, the development of appropriate energy storage technologies plays a key role in the feasibility of such an electric helicopter due to the necessity to achieve adequate endurance.


Diaz-Banez J.M.,University of Seville | Korman M.,Polytechnic University of Catalonia | Perez-Lantero P.,University of Valparaiso | Pilz A.,Graz University of Technology | And 2 more authors.
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2013

We consider a natural variation of the concept of stabbing a segment by a simple polygon: a segment is stabbed by a simple polygon P if at least one of its two endpoints is contained in P. A segment set S is stabbed by P if every segment of S is stabbed by P. We show that if S is a set of pairwise disjoint segments, the problem of computing the minimum perimeter polygon stabbing S can be solved in polynomial time. We also prove that for general segments the problem is NP-hard. Further, an adaptation of our polynomial-time algorithm solves an open problem posed by Löffler and van Kreveld [Algorithmica 56(2), 236-269 (2010)] about finding a maximum perimeter convex hull for a set of imprecise points modeled as line segments. © 2013 Springer-Verlag.


Polzler M.,CEST Center Of Electrochemical Surface Technology | Whitehead A.H.,CEST Center Of Electrochemical Surface Technology | Gollas B.,CEST Center Of Electrochemical Surface Technology | Gollas B.,Graz University of Technology
ECS Transactions | Year: 2010

This work is an initial study of the zinc deposition process from a Lewis-basic choline chloride/ ethylene glycol deep eutectic solvent containing ZnCl2 at 30°C. The system was examined by cyclic voltammetry at static and rotating glassy carbon disc electrodes and by potential step techniques. Although there was little deposition initially on sweeping or stepping the potential to -0.5 to -0.8 V vs. Zn/Zn(II) more rapid deposition was observed when the potential was raised to -0.4 to -0.2 V. The role of choline chloride was also examined by comparison with a choline-free electrolyte, which exhibited a more conventional voltammetric response. A tentative suggestion has been proposed to account for the observed deposition behaviour. ©The Electrochemical Society.


Hadlak S.,University of Rostock | Schulz H.-J.,Graz University of Technology | Schumann H.,University of Rostock
IEEE Transactions on Visualization and Computer Graphics | Year: 2011

The analysis of large dynamic networks poses a challenge in many fields, ranging from large bot-nets to social networks. As dynamic networks exhibit different characteristics, e.g., being of sparse or dense structure, or having a continuous or discrete time line, a variety of visualization techniques have been specifically designed to handle these different aspects of network structure and time. This wide range of existing techniques is well justified, as rarely a single visualization is suitable to cover the entire visual analysis. Instead, visual representations are often switched in the course of the exploration of dynamic graphs as the focus of analysis shifts between the temporal and the structural aspects of the data. To support such a switching in a seamless and intuitive manner, we introduce the concept of in situ visualization– a novel strategy that tightly integrates existing visualization techniques for dynamic networks. It does so by allowing the user to interactively select in a base visualization a region for which a different visualization technique is then applied and embedded in the selection made. This permits to change the way a locally selected group of data items, such as nodes or time points, are shown – right in the place where they are positioned, thus supporting the user's overall mental map. Using this approach, a user can switch seamlessly between different visual representations to adapt a region of a base visualization to the specifics of the data within it or to the current analysis focus. This paper presents and discusses the in situ visualization strategy and its implications for dynamic graph visualization. Furthermore, it illustrates its usefulness by employing it for the visual exploration of dynamic networks from two different fields: model versioning and wireless mesh networks. © 2011 IEEE.


Medwed M.,Graz University of Technology | Standaert F.-X.,Catholic University of Louvain | Grossschadl J.,University of Luxembourg | Regazzoni F.,Catholic University of Louvain
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2010

The market for RFID technology has grown rapidly over the past few years. Going along with the proliferation of RFID technology is an increasing demand for secure and privacy-preserving applications. In this context, RFID tags need to be protected against physical attacks such as Differential Power Analysis (DPA) and fault attacks. The main obstacles towards secure RFID are the extreme constraints of passive tags in terms of power consumption and silicon area, which makes the integration of countermeasures against physical attacks even more difficult than for other types of embedded systems. In this paper we propose a fresh re-keying scheme that is especially suited for challenge-response protocols such as used to authenticate tags. We evaluate the resistance of our scheme against fault and side-channel analysis, and introduce a simple architecture for VLSI implementation. In addition, we estimate the cost of our scheme in terms of area and execution time for various security/performance trade-offs. Our experimental results show that the proposed re-keying scheme provides better security (and does so at less cost) than state-of-the-art countermeasures. © 2010 Springer-Verlag.


Teufl P.,Graz University of Technology | Payer U.,University of Graz | Lackner G.,Studio78
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2010

Natural Language Processing (NLP) in combination with Machine Learning techniques plays an important role in the field of automatic text analysis. Motivated by the successful use of NLP in solving text classification problems in the area of e-Participation and inspired by our prior work in the field of polymorphic shellcode detection we gave classical NLP-processes a trial in the special case of malicious code analysis. Any malicious program is based on some kind of machine language, ranging from manually crafted assembler code that exploits a buffer overflow to high level languages such as Javascript used in web-based attacks. We argue that well known NLP analysis processes can be modified and applied to the malware analysis domain. Similar to the NLP process we call this process Machine Language Processing (MLP). In this paper, we use our e-Participation analysis architecture, extract the various NLP techniques and adopt them for the malware analysis process. As proof-of-concept we apply the adopted framework to malicious code examples from Metasploit. © Springer-Verlag 2010.


Krenn J.R.,University of Graz | Galler N.,University of Graz | Ditlbacher H.,University of Graz | Hohenau A.,University of Graz | And 4 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2011

Optoelectronical components and devices based on organic materials offer a wealth of possibilities in terms of integration, miniaturization and potentially low-cost fabrication for relevant applications, notwithstanding a performance that may fall short of conventional state-of-the-art systems. In this context we report on progress towards the combination of surface plasmon resonance (SPR) sensing with a monolithically integrated optical sensor platform based on organic materials, including an organic light emitting diode, an optical polymer waveguide and an organic photo diode. Several according components have been developed and demonstrated recently and were exemplarily applied to fluorescence lifetime detection. Aiming at multianalyte performance we add SPR to this platform, which enables the sensitive, real-time and label-free detection of a wide range of analytes. The SPR detection scheme is based on a gold surface sustaining a surface plasmon mode which reacts sensitively to analyte-induced refractive index changes. Here, we report on the investigation of the sensor response of a 50 nm thick gold film on an 11 μm thick multimode polymer waveguide. The feasibility of this sensor concept is shown and its sensitivity is estimated from measuring the intensity transmitted trough the waveguide at a single wavelength. In addition, some further steps towards full integration are discussed. © 2011 SPIE.


Cela E.,Graz University of Technology | Deineko V.G.,University of Warwick | Woeginger G.J.,TU Eindhoven
Journal of Combinatorial Optimization | Year: 2014

We consider special cases of the quadratic assignment problem (QAP) that are linearizable in the sense of Bookhold. We provide combinatorial characterizations of the linearizable instances of the weighted feedback arc set QAP, and of the linearizable instances of the traveling salesman QAP. As a by-product, this yields a new well-solvable special case of the weighted feedback arc set problem. © 2014 Springer Science+Business Media New York


Spreitzer R.,Graz University of Technology
Proceedings of the ACM Conference on Computer and Communications Security | Year: 2014

The pervasive usage of mobile devices, i.e., smartphones and tablet computers, and their vast amount of sensors represent a plethora of side channels posing a serious threat to the user's privacy and security. In this paper, we propose a new type of side channel which is based on the ambient-light sensor employed in today's mobile devices. While recent advances in this area of research focused on the employed motion sensors and the camera as well as the sound, we investi- gate a less obvious source of information leakage, namely the ambient light. We successfully demonstrate that minor tilts and turns of mobile devices cause variations of the ambient- light sensor information. Furthermore, we show that these variations leak enough information to infer a user's personal identification number (PIN) input based on a set of known PINs. Our results clearly show that we are able to determine the correct PIN|out of a set of 50 random PINs|within the first ten guesses about 80% of the time. In contrast, the chance of finding the right PIN by randomly guessing ten PINs would be 20%. Since the data required to perform such an attack can be gathered without any specific permissions or privileges, the presented attack seriously jeopardizes the security and privacy of mobile-device owners. Copyright © 2014 by the Association for Computing Machinery, Inc. (ACM).


Henzinger M.R.,Graz University of Technology | Galler R.,University of Leoben
Rock Engineering and Rock Mechanics: Structures in and on Rock Masses - Proceedings of EUROCK 2014, ISRM European Regional Symposium | Year: 2014

As only a small part of the tunnel face of a TBM-driven tunnel can be inspected visually, a photographic documentation was tested, in order to get a more holistic picture. For this purpose a standard photographic camerawas installed in one of the manholes of the cutterhead. During one rotation of the cutterhead the camera takes a video of the tunnel face. For post-processing of the acquired data, a script was developed, that compares the individual frames of the video and aligns them in order to generate an overall picture. The distance between the individual frames of the video was determined by comparing two adjacent phase-correlated images. This method uses the fourier transformation for the calculation of the distances between the images. The quality of the created images is independent from the distance between the camera and the tunnel face as well as the rotation direction of the cutter head. © 2014 Taylor & Francis Group, London.


Potsch M.,3GSM GmbH | Schubert W.,Graz University of Technology
Rock Engineering and Rock Mechanics: Structures in and on Rock Masses - Proceedings of EUROCK 2014, ISRM European Regional Symposium | Year: 2014

The kinematic analysis of rock blocks is a part of a block stability assessment. It provides information about a block's movability, i.e. if a block can detach from the adjacent rock mass and move towards the free space. This paper introduces a new analytical method for the analysis of pure rotations of arbitrary finite polyhedral blocks. It enables the engineer to judge a block's rotatability about a corner or an edge. The application of the method is illustrated with an example. © 2014 Taylor & Francis Group, London.


Bucher E.,University of Leoben | Gspan C.,Graz University of Technology | Sitte W.,University of Leoben
Solid State Ionics | Year: 2015

The impact of long-term exposure of La0.6Sr0.4CoO3 - δ to SO2-containing atmospheres was investigated. In-situ dc-conductivity relaxation measurements showed a decrease in the chemical surface exchange coefficient of oxygen (kchem) during the course of 1000 h in an atmosphere with either a few ppb or 2 ppm SO2 at 700 C. Post-test analyses by scanning electron microscopy with energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and analytical transmission electron microscopy indicated that SrSO4 crystals with diameters of 100 nm-1 μm are formed during the degradation, in addition to a nanocrystalline 100-300 nm thick multi-phase layer and LaCoO3 - δ at grain boundaries. In order to regenerate the degraded sample, a thermal treatment was applied. It could be shown that a partial re-activation of the degraded specimen takes place at 750-850 C even in an atmosphere with 2 ppm SO2. This regeneration is ascribed to the in-situ formation of catalytically active LaCoO3 - δ nanoparticles at the surface. However, a subsequent degradation follows independently of the SO2 content of the atmosphere when the sample is kept for 1000 h at 850-900 C. Post-test analyses indicate that this effect is due to a strong grain growth of the LaCoO3 - δ nanocrystals which leads to a loss in the catalytic activity. © 2015 Elsevier B.V. All rights reserved.


Gaich A.,3GSM GmbH | Potsch M.,3GSM GmbH | Schubert W.,Graz University of Technology
Rock Engineering and Rock Mechanics: Structures in and on Rock Masses - Proceedings of EUROCK 2014, ISRM European Regional Symposium | Year: 2014

This contribution describes the application of 3D images for rock mass characterisation and focusses on the determination of joint spacing as well as several volumetric measurements. © 2014 Taylor & Francis Group, London.


Schubert W.,Graz University of Technology
Rock Engineering and Rock Mechanics: Structures in and on Rock Masses - Proceedings of EUROCK 2014, ISRM European Regional Symposium | Year: 2014

Uncertainties in the geological and ground models prior to construction lead to a residual risk during construction. As well the ground properties, as the exact location of the single units are not known precisely during the design. In addition, factors influencing the ground and system behavior, like ground stresses and ground water conditions can be estimated only in this stage. The consequence is a residual risk during construction.To minimize the risk, an observational approach is required. This involves sound preparation during design, and special procedures to be followed during construction. Part of these procedures is the geotechnical safety management, which will be presented in this paper. © 2014 Taylor & Francis Group, London.


Kober S.E.,University of Graz | Neuper C.,University of Graz | Neuper C.,Graz University of Technology
International Journal of Human Computer Studies | Year: 2012

The feeling of presence in a virtual reality (VR) is a concept without a standardized objective measurement. In the present study, we used event-related brain potentials (ERP) of the electroencephalogram (EEG) elicited by tones, which are not related to VR, as an objective indicator for the presence experience within a virtual environment. Forty participants navigated through a virtual city and rated their sensation of being in the VR (experience of presence), while hearing frequent standard tones and infrequent deviant tones, which were irrelevant for the VR task. Different ERP components elicited by the tones were compared between participants experiencing a high level of presence and participants with a low feeling of presence in the virtual city. Early ERP components, which are more linked to automatic stimulus processing, showed no correlation with presence experience. In contrast, an increased presence experience was associated with decreased late negative slow wave amplitudes, which are associated with central stimulus processing and allocation of attentional resources. This result supports the assumption that increased presence is associated with a strong allocation of attentional resources to the VR, which leads to a decrease of attentional resources available for processing VR-irrelevant stimuli. Hence, ERP components elicited by the tones are reduced. Particularly, frontal negative slow waves turned out to be accurate predictors for presence experience. Summarizing, late ERPs elicited by VR-irrelevant tones differ as a function of presence experience in VR and provide a valuable method for measuring presence in VR. © 2012 Elsevier Ltd.


Zellnitz S.,Research Center Pharmaceutical Engineering GmbH | Schroettner H.,Graz University of Technology | Urbanetz N.A.,Research Center Pharmaceutical Engineering GmbH
Drug Development and Industrial Pharmacy | Year: 2015

The aim of this work is to investigate the effect of surface characteristics (surface roughness and specific surface area) of surface-modified glass beads as model carriers in dry powder inhalers (DPIs) on the aerosolization, and thus, the in vitro respirable fraction often referred to as fine particle fraction (FPF). By processing glass beads in a ball mill with different grinding materials (quartz and tungsten carbide) and varying grinding time (4 h and 8 h), and by plasma etching for 1 min, glass beads with different shades of surface roughness and increased surface area were prepared. Compared with untreated glass beads, the surface-modified rough glass beads show increased FPFs. The drug detachment from the modified glass beads is also more reproducible than from untreated glass beads indicated by lower standard deviations for the FPFs of the modified glass beads. Moreover, the FPF of the modified glass beads correlates with their surface characteristics. The higher the surface roughness and the higher the specific surface area of the glass beads the higher is the FPF. Thus, surface-modified glass beads make an ideal carrier for tailoring the performance of DPIs in the therapy of asthma and chronically obstructive pulmonary diseases. © 2015 Informa Healthcare USA, Inc.


Mowlaee P.,Graz University of Technology | Saeidi R.,Aalto University | Stylianou Y.,University of Crete
Speech Communication | Year: 2016

During the past three decades, the issue of processing spectral phase has been largely neglected in speech applications. There is no doubt that the interest of speech processing community towards the use of phase information in a big spectrum of speech technologies, from automatic speech and speaker recognition to speech synthesis, from speech enhancement and source separation to speech coding, is constantly increasing. In this paper, we elaborate on why phase was believed to be unimportant in each application. We provide an overview of advancements in phase-aware signal processing with applications to speech, showing that considering phase-aware speech processing can be beneficial in many cases, while it can complement the possible solutions that magnitude-only methods suggest. Our goal is to show that phase-aware signal processing is an important emerging field with high potential in the current speech communication applications. The paper provides an extended and up-to-date bibliography on the topic of phase aware speech processing aiming at providing the necessary background to the interested readers for following the recent advancements in the area. Our review expands the step initiated by our organized special session and exemplifies the usefulness of spectral phase information in a wide range of speech processing applications. Finally, the overview will provide some future work directions. © 2016 Elsevier B.V.


By implementation of the Eurocodes the part EN 1993-4-3 "Pipelines "has also been published. Its real status within the wide field of existing pipeline-standards for various applications needs closer explanation. In the ÖNORM B 1993-4, i.e. the Austrian National Annex of the above Eurocode, such a commentary is given as well as additional rules for pressure piping of hydro-power plants which so far were not covered by specific standardization. Although, presently restricted in application to power plants of limited magnitudes of internal pressure and pipe diameter the general concept and the background may be taken from this paper. © Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.


Wittig M.,MEW Aerospace | Koudelka O.,Graz University of Technology | Frischauf N.,SpaceTech Partners
Proceedings of the International Astronautical Congress, IAC | Year: 2013

Satellite based AIS missions for vessel detection and identification are a reality and satellite based ADS-B missions for aircraft detection and tracking are at the verge to be a reality soon. A novel concept to avoid the signal collisions was presented by a previous paper at IAC 2012 [I]. The objective of this paper is to present the details of the novel antenna concept based on phased array technology and on-ground beam forming flying on nano/micro satellites. A detailed analysis of the interference scenarios for the AIS case was presented already at the previous paper. Missinn is a similar analvsis for the ADS-B case - required to derive the Phased Array Antenna size. Due to the use of different flight levels in commercial air transport a criteria similar to the AIS case was not found. Instead a generic interference analysis is performed based on the assumption that the number of aircrafts in highly dense controlled air-traffic space is proportional to the geographic area. The results of such an interference analysis are used to find an optimized size of the phased array antenna, taking as a major constraint into account the required downlink bandwidth. The implementation of the required boom on a nano/micro-satellite is a challenge but essential for mission success. Finally options for the implementation of such booms will be discussed as well. ©2013 by the International Astronautical Federation. All rights reserved.


Hofferek G.,Graz University of Technology | Gupta A.,IST
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2014

Boolean controllers for systems with complex datapaths are often very difficult to implement correctly, in particular when concurrency is involved. Yet, in many instances it is easy to formally specify correctness. For example, the specification for the controller of a pipelined processor only has to state that the pipelined processor gives the same results as a non-pipelined reference design. This makes such controllers a good target for automated synthesis. However, an efficient abstraction for the complex datapath elements is needed, as a bit-precise description is often infeasible. We present Suraq, the first controller synthesis tool which uses uninterpreted functions for the abstraction. Quantified firstorder formulas (with specific quantifier structure) serve as the specification language from which Suraq synthesizes Boolean controllers. Suraq transforms the specification into an unsatisfiable SMT formula, and uses Craig interpolation to compute its results. Using Suraq, we were able to synthesize a controller (consisting of two Boolean signals) for a five-stage pipelined DLX processor in roughly one hour and 15 minutes. © Springer International Publishing Switzerland 2014.


Walk S.,Graz University of Technology | Singer P.,GESIS Leibniz Institute for the Social science | Strohmaier M.,GESIS Leibniz Institute for the Social science | Strohmaier M.,University of Koblenz-Landau | And 3 more authors.
Journal of Biomedical Informatics | Year: 2014

Biomedical taxonomies, thesauri and ontologies in the form of the International Classification of Diseases as a taxonomy or the National Cancer Institute Thesaurus as an OWL-based ontology, play a critical role in acquiring, representing and processing information about human health. With increasing adoption and relevance, biomedical ontologies have also significantly increased in size. For example, the 11th revision of the International Classification of Diseases, which is currently under active development by the World Health Organization contains nearly 50, 000 classes representing a vast variety of different diseases and causes of death. This evolution in terms of size was accompanied by an evolution in the way ontologies are engineered. Because no single individual has the expertise to develop such large-scale ontologies, ontology-engineering projects have evolved from small-scale efforts involving just a few domain experts to large-scale projects that require effective collaboration between dozens or even hundreds of experts, practitioners and other stakeholders. Understanding the way these different stakeholders collaborate will enable us to improve editing environments that support such collaborations. In this paper, we uncover how large ontology-engineering projects, such as the International Classification of Diseases in its 11th revision, unfold by analyzing usage logs of five different biomedical ontology-engineering projects of varying sizes and scopes using Markov chains. We discover intriguing interaction patterns (e.g., which properties users frequently change after specific given ones) that suggest that large collaborative ontology-engineering projects are governed by a few general principles that determine and drive development. From our analysis, we identify commonalities and differences between different projects that have implications for project managers, ontology editors, developers and contributors working on collaborative ontology-engineering projects and tools in the biomedical domain. © 2014 Elsevier Inc.


Preschern C.,Graz University of Technology
ACM International Conference Proceeding Series | Year: 2014

Peer reviews and feedback from colleagues give an author other opinions and suggestions to improve a scientific paper. To provide guidance for giving such feedback, this paper presents patterns on how to find, structure, and give feedback on scientific papers. Additionally this paper gives an overview of literature on reviewing scientific papers.


Kerschbaumer A.,Research Center | Hirschberg W.,Graz University of Technology | Prezel D.,AVL List GmbH
The Dynamics of Vehicles on Roads and Tracks - Proceedings of the 24th Symposium of the International Association for Vehicle System Dynamics, IAVSD 2015 | Year: 2016

Nowadays, the tyre parameters are determined by measurements on the tyre test rig and manually adapted to real road conditions before they are used for a credible vehicle dynamic simulation. This requires relevant expertise of the user or it must be accepted that results of the simulation can differ significantly from the behaviour of the tyre on the track. At this point the question arises how it is possible to make the actual procedure of tyre model parameterisation more efficient and safer. This paper illustrates a new procedure to adapt MF-Tyre model parameters to real road conditions. It replaces the necessity of the elaborate manual modification of the MF-Tyre model parameters. Beyond this, basic tyre properties can be identified without the need of tests at the test rig. Studies have shown that the adaptation of the basis MF-Tyre parameter set already leads to a significant improvement of the simulation quality. © 2016 Taylor & Francis Group, London.


Baldermann A.,University of Greifswald | Baldermann A.,Graz University of Technology | Grathoff G.H.,University of Greifswald | Nickel C.,University of Greifswald
Clay Minerals | Year: 2012

Although numerous models for the formation of glauconite have been presented, the precise process and micro-environment of glauconitization are still poorly constrained. We characterize the special micromilieu of glauconitization developed during early diagenesis and present a model for glauconite formation in fecal pellets. Glauconitization at Oker (Central Germany) occurred predominantly in fecal pellets deposited in a shallow marine-lagoonal environment during the Kimmeridgian. Within the fecal pellets, rapid oxidation of organic matter provides the post-depositional, physicochemical conditions favourable for glauconitization. Replacements of matrix calcite, dissolution of detrital quartz, K-feldspar, and clay minerals, and Fe redox reactions were observed within the early micro-environment, followed by the precipitation of euhedral pyrite, matrix-replacive dolomite, and megaquartz accompanied by IS formation as thin section analyses and SEM observations show. Carbonate geochemical compositions based on ICP-OES and stable oxygen and carbon isotope signatures demonstrate that glauconite formation started in a suboxic environment at a pH of 7-8 and a temperature of 22±3°C to 37±2°C at maximum. TEM-EDX-SAED and XRD analyses on separated glauconite fecal pellets and on the <2 μm clay mineral fraction reveal the predominance of authigenic 1Md-glauconite, 1Md-glauconite-smectite, and 1Md cis-vacant I-S, besides accessory detrital 2M1-illite and montmorillonite. Kinetic modelling of the glauconite (93-94% Fe-illite layers and 6-7% Fe-smectite layers, R3) and of I-S (66-68% Al-illite layers and 32-34% Al-smectite layers, R1) leads us to conclude that the I-S formed solely by slow burial diagenesis, whereas the glauconite formed close to the seafloor, suggesting significantly faster kinetics of the glauconitization reaction compared with smectite-illitization related to burial diagenesis. Thermodynamically, the substitution of octahedral Al3+ for Fe3+ and Mg2+ during the Fe-Mg-smectite to glauconite reaction via the formation of glauconite-smectite mixed-layered clay minerals may have resulted in a higher reaction rate for this low-temperature glauconitization process. © 2012 The Mineralogical Society.


Fessl A.,Know Center | Feyertag S.,Know Center | Pammer V.,Graz University of Technology
ACM International Conference Proceeding Series | Year: 2015

This paper presents a case study on co-designing digital technologies for knowledge management and data-driven business for an SME. The goal of the case study was to analyse the status quo of technology usage and to develop design suggestions in form of mock-ups tailored to the company's needs. We used both requirements engineering and interactive system design methods such as interviews, workshops, and mock-ups for work analysis and system design. The case study illustrates step-by-step the processes of knowledge extraction and combination (analysis) and innovation creation (design). These processes resulted in non-functional mockups, which are planned to be implemented within the SME. © 2015 ACM.


Holzinger A.,Medical University of Graz | Holzinger A.,Graz University of Technology
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2014

Humans are very good at pattern recognition in dimensions of ≤ 3. However, most of data, e.g. in the biomedical domain, is in dimensions much higher than 3, which makes manual analyses awkward, sometimes practically impossible. Actually, mapping higher dimensional data into lower dimensions is a major task in Human-Computer Interaction and Interactive Data Visualization, and a concerted effort including recent advances in computational topology may contribute to make sense of such data. Topology has its roots in the works of Euler and Gauss, however, for a long time was part of theoretical mathematics. Within the last ten years computational topology rapidly gains much interest amongst computer scientists. Topology is basically the study of abstract shapes and spaces and mappings between them. It originated from the study of geometry and set theory. Topological methods can be applied to data represented by point clouds, that is, finite subsets of the ndimensional Euclidean space. We can think of the input as a sample of some unknown space which one wishes to reconstruct and understand, and we must distinguish between the ambient (embedding) dimension n, and the intrinsic dimension of the data. Whilst n is usually high, the intrinsic dimension, being of primary interest, is typically small. Therefore, knowing the intrinsic dimensionality of data can be seen as one first step towards understanding its structure. Consequently, applying topological techniques to data mining and knowledge discovery is a hot and promising future research area. © Springer-Verlag Berlin Heidelberg 2014.


Aichholzer O.,Graz University of Technology
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2014

In a good drawing of a complete graph the vertices are drawn as distinct points in the plane, edges are drawn as non-self-intersecting continuous arcs connecting its two end points, but not passing through any other point representing a vertex. Moreover, any pair of edges intersects at most once, either in their interior or at a common endpoint, no tangencies are allowed and no three edges pass through a single crossing. These drawings are also called simple topological graphs.A rotation system (of a good drawing of a complete graph) gives, for each vertex v of the graph, the circular ordering around v of all edges incident to v. In combinatorial mathematics, rotation systems were first used by Hefner in 1891 to encode embeddings of graphs onto orientable surfaces, determining its genus. In the plane (or equivalently on the sphere) the rotation system of a good drawing does not fully determine the drawing, but contains combinatorial information like all pairs of edges which intersect.We present basic properties of these two concepts, as well as recent progress. This includes results on the number of realizable rotation systems, the crossing number of complete graphs (including the recent concept of shellability of a good drawing), relations to other systems like the order type of a point set, etc. © Springer-Verlag Berlin Heidelberg 2014.


Deng X.,Ecole Polytechnique - Palaiseau | Deng X.,Japan Science and Technology Agency | Ferrero M.,Ecole Polytechnique - Palaiseau | Mravlje J.,Ecole Polytechnique - Palaiseau | And 6 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

Recent angular-resolved photoemission experiments on LaNiO 3 reported a renormalization of the Fermi velocity of e g quasiparticles, a kink in their dispersion at -0.2 eV and a large broadening and weakened dispersion of the occupied t 2g states. We show here that all these features result from electronic correlations and are quantitatively reproduced by calculations combining density-functional theory and dynamical mean-field theory. The importance and general relevance of correlation effects in filled bands coupled by interorbital interactions to a partially filled band are pointed out. © 2012 American Physical Society.


Parada I.,Graz University of Technology | Sacristan V.,Polytechnic University of Catalonia | Silveira R.I.,Polytechnic University of Catalonia
Proceedings - IEEE International Conference on Robotics and Automation | Year: 2016

We present a robust and compact meta-module for edge-hinged modular robot units such as M-TRAN, SuperBot, SMORES, UBot, PolyBot and CKBot, as well as for central-point-hinged ones such as Molecubes and Roombots. Thanks to the rotational degrees of freedom of these units, the novel meta-module is able to expand and contract, as to double/halve its length in each dimension. Moreover, for a large class of edge-hinged robots the proposed meta-module also performs the scrunch/relax and transfer operations required by any tunneling-based reconfiguration strategy, such as those designed for Crystalline and Telecube robots. These results make it possible to apply efficient geometric reconfiguration algorithms to this type of robots. We prove the size of this new meta-module to be optimal. Its robustness and performance substantially improve over previous results. © 2016 IEEE.


Plated girders with longitudinally stiffened webs, used for example as main girders for steel and composite bridges, are now designed based on the Eurocode EN 1993-1-5. Applying the traditional used reduced stress method, for practical examples often conservative results - compared to the old national codes (ÖNORM, DIN) - are found. Based on this fact, nonlinear calculations were done to compare the ultimate plate buckling load with the design in the Eurocode. The results of the study are presented in this paper as well as an improved rule to get better results with the Eurocode. At the beginning the design rules of the Eurocode are briefly summarised and the differences compared to the existing national codes are presented. After that the studied stiffened web panels and their plate buckling capacity-based on the nonlinear calculations as well as on the rules of the Eurocode - are summed up. Finally the improved rules are presented and some recommendations for practical design are given. © Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.


Bagavathiannan M.V.,University of Manitoba | Spok A.,Graz University of Technology | van Acker R.C.,University of Guelph
Journal of Agricultural and Environmental Ethics | Year: 2011

Overall, the deregulation of genetically engineered (GE) crops for commercial cultivation in North America has been a success story. In several cases, however, GE crops have sparked concerns and disagreements among the stakeholders and there are incidences of court lawsuits, including a recent one on glyphosate resistant (GR) alfalfa (Medicago sativa, L.). While GE crops can provide operational benefits to farmers, challenges are looming from commercialization of perennial GE crops. The unique ecology and biology of these crops and GE alfalfa in particular can facilitate adventitious presence (AP) of GE traits and it makes more visible that economic risks for conventional growers and food/feed producers have not been adequately addressed by the GE regulatory system in the United States (US). Asynchronous market approvals and the existence of a number of GE sensitive export markets create uncertainties among the exporters. Policy development in these fields may be helpful for ensuring a broader acceptance and market success of GE agriculture in general. The analysis is focusing on the US, although many diagnosed problems are also relevant to other jurisdictions-in particular if no co-existence policy is in place. © 2010 Springer Science+Business Media B.V.


Faist J.,University of Graz | Seebacher W.,University of Graz | Kaiser M.,Swiss Tropical Institute | Brun R.,Swiss Tropical Institute | And 2 more authors.
European Journal of Medicinal Chemistry | Year: 2010

N-Alkyl and N-(2-dialkylaminoethyl) derivatives of 5-amino-2-azabicyclo-nonanes were prepared and tested in vitro for their activities against the multidrug-resistant K1 strain of Plasmodium falciparum and Trypanosoma brucei rhodesiense (STIB 900). Most of the new compounds showed lower antitrypanosomal activity than their parent compounds. With respect to their activity against P. falciparum the N-alkyl derivatives exhibited worse selectivity due to decreased antiplasmodial activity or higher cytotoxicity. In comparison all of the new N-(2-dialkylaminoethyl) analogues possessed a much better selectivity and a single of these compounds showed even better antiplasmodial activity and selectivity than chloroquine. © 2009 Elsevier Masson SAS. All rights reserved.


Cheung W.,University of Washington | Sarma D.,University of Washington | Scherer R.,Graz University of Technology | Rao R.P.N.,University of Washington
Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS | Year: 2012

Brain-computer interfaces (BCIs) have traditionally been developed for paralyzed and locked-in individuals with no motor control. However, there is a much larger population of patients with some residual motor function as well as the general population of able-bodied individuals, both of whom could benefit significantly from BCIs. An important question that has yet to be systematically studied is: can subjects use BCIs simultaneously with overt motor activity? We present results from a preliminary study aimed at exploring this question. Three subjects used hand motor imagery in an electroencephalographic (EEG) BCI while simultaneously using a joystick to control a cursor. Particular attention was paid to preventing potential muscle artifacts from influencing imagery-based control. All three subjects were able to use the hybrid imagery+joystick mode of control over two days, demonstrating the ability to learn and significantly improve performance. These results suggest that subjects can potentially augment their normal human sensorimotor capability by exercising direct brain control over devices concurrently with overt motor control. © 2012 IEEE.


Kern R.,Know Center | Juffinger A.,Know Center | Granitzer M.,Know Center | Granitzer M.,Graz University of Technology
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2010

Integrating word sense disambiguation into an information retrieval system could potentially improve its performance. This is the major motivation for the Robust WSD tasks of the Ad-Hoc Track of the CLEF 2009 campaign. For these tasks we have build a customizable and flexible retrieval system. The best performing configuration of this system is based on research in the area of axiomatic approaches to information retrieval. Further, our experiments show that configurations that incorporate word sense disambiguation (WSD) information into the retrieval process did outperform those without. For the monolingual task the performance difference is more pronounced than for the bilingual task. Finally, we are able to show that our query translation approach does work effectively, even if applied in the monolingual task. © 2010 Springer-Verlag Berlin Heidelberg.


Kern R.,Know Center | Granitzer M.,Know Center | Granitzer M.,Graz University of Technology
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2010

Collaboratively created online encyclopedias have become increasingly popular. Especially in terms of completeness they have begun to surpass their printed counterparts. Two German publishers of traditional encyclopedias have reacted to this challenge and decided to merge their corpora to create a single more complete encyclopedia. The crucial step in this merge process is the alignment of articles. We have developed a system to identify corresponding entries from different encyclopedic corpora. The base of our system is the alignment algorithm which incorporates various techniques developed in the field of information retrieval. We have evaluated the system on four real-world encyclopedias with a ground truth provided by domain experts. A combination of weighting and ranking techniques has been found to deliver a satisfying performance. © 2010 Springer-Verlag Berlin Heidelberg.


Tomantschger K.W.,Graz University of Technology | Petrovic D.V.,University of Belgrade | Golubovic Z.D.,University of Belgrade | Mileusnic Z.I.,University of Belgrade
African Journal of Agricultural Research | Year: 2011

A novel mathematical model for the tractor engine durability, based on the appropriate differential equation and conditions, is formulated and presented in this paper. Its practical applicability is experimentally verified for the tractor type Massey-Ferguson 8160. The probability density function of the engine's lifespan, as long as the overhaul is needed, is established and approximated by normal Gaussian function. Fitting coefficients are evaluated through the non-linear fitting of empirical data by Levenberg-Marquardt numerical algorithm. © 2011 Academic Journals.


Kerschbaum F.,SAP | Aigner M.,Graz University of Technology
Cryptology and Information Security Series | Year: 2010

Modern RFID-supported supply chains envision a seamless sharing of item-level data across multiple supply chain participants in the "Internet of Things". However, many companies are reluctant to propagate large amounts of their track and trace information to others, as they fear the uncontrolled disclosure of vital business intelligence. Without built-in safeguards, such systems thus run the risk of hindering the adoption of efficient supply chain management infrastructures. In this paper we will define the cornerstones of a cryptographically sound security architecture for RFID-supported supply chains that will enable efficient logistical management with minimal data disclosure. We propose to replace the common centralized track and trace approach with an architecture that makes use of strong cryptographic primitives and secure storage on the tag and builds on top of those enhanced authentication and key-agreement protocols. The architecture will thus span the entire technology range from the RFID tag and its network infrastructure to the back-end system that is storing the supply chain information. © 2010 The authors and IOS Press. All rights reserved.


Lackner H.K.,Institute of Adaptive and Spaceflight Physiology | Lackner H.K.,Medical University of Graz | Goswami N.,Medical University of Graz | Hinghofer-Szalkay H.,Institute of Adaptive and Spaceflight Physiology | And 5 more authors.
Journal of Psychophysiology | Year: 2010

Studies examining the direct effects of stimuli needed to perform mental stress tasks such as instructor commands at regular intervals during the mental task are limited to date. Because of the comprehensive effects of different stimuli, we studied the effect of short instructor commands occurring at regular intervals on the behavior of the cardiovascular system during two different types of tasks. Continuous beat-to-beat heart rate and blood pressure, respiration, thoracic impedance, skin conductance, and peripheral temperature were measured in 20 healthy females during a cancellation test of attention (stimuli interval of 20 s) and during mental arithmetic tasks (stimuli interval of 120 s). The transient effects of the stimuli on measures in the time domain as well as the effects of stimulus intervals on measures in the frequency domain (using spectral analysis) were examined. Instructor commands caused increases in several cardio-vascular variables and in skin conductance. SBP (systolic blood pressure) and DBP (diastolic blood pressure) showed a significant stimulus response only during the mental arithmetic tasks. An effect of instructor commands at regular intervals was seen in the spectral analysis at 0.05 Hz (cancellation test of attention) and 1/120 Hz (mental arithmetic), according to the stimulus intervals of 20 s and 120 s used in these tasks. The findings suggest that even simple instructor commands given during high mental task load had a strong impact and can considerably influence measures of cardiovascular reactivity. The effects of paced stimuli should be considered when interpreting cardiovascular responses to task conditions with constant stimulus intervals. © 2010 Federation of European Psychophysiology Societies.


Griesmayer A.,UNU IIST | Staber S.,OneSpin Solutions | Bloem R.,Graz University of Technology
Software Testing Verification and Reliability | Year: 2010

If a program does not fulfill its specification, a model checker can deliver a counterexample. However, although such a counterexample shows how the specification can be violated, it typically comprises large parts of the program and gives little information about which of the visited statements is responsible for the error. In this article, we show that model checkers can also be used to perform model-based diagnosis and thus fault localization. The approach leads to significantly more precise diagnoses than the state-of-the-art and typically rules out 90-99% of the code as possible fault locations. The approach is general and can be applied to any system that is amenable to model checking (with respect to language and complexity). To demonstrate the applicability and high precision of our approach, we present implementations for C programs using two different model checking tools and show experimental results from the TCAS case study and an integration with the DDVerify framework to debug Linux device drivers. Copyright © 2009 John Wiley & Sons, Ltd.


Maydl P.,Graz University of Technology
Global Thinking in Structural Engineering: Recent Achievements | Year: 2012

As opposed to the financial sector structural engineers are used to avoid reaching ultimate state limits of a structure since centuries. From the old Romans till this day requirements on buildings and construction works have been increased tremendously. Life cycle design and sustainable construction require not only functionality, comfort and structural safety for the entire lifetime of a building, but amongst others also resource efficiency, recyclability and durability for the reference service life. These new challenges cause an advanced responsibility of architects and particularly of structural engineers for society and future generations. As civil engineers move more and more to civilization engineers they should ask themselves if they bequeath their children a better world than they were born into.


Schuss C.,University of Oulu | Eichberger B.,Graz University of Technology | Rahkonen T.,University of Oulu
2014 IEEE 11th International Multi-Conference on Systems, Signals and Devices, SSD 2014 | Year: 2014

This paper discusses design requirements to efficiently gather solar energy for mobile phones. It examines current system structures such as conventional solar chargers with an aim to highlight evident weaknesses in existing system structures. Based on the analysis, the paper presents measurement results that indicate that prevailing strategies are not sophisticated enough to meet smartphone users expectations. It is important to note that the recharging time and the quantity of energy required for operational smartphones are critical. We propose design specifications that make solar changers competitive in terms of expenses when compared with universal serial bus (USB) chargers. © 2014 IEEE.


Yogendra S.,TU Dresden | Chitnis S.S.,University of Victoria | Hennersdorf F.,TU Dresden | Bodensteiner M.,University of Regensburg | And 3 more authors.
Inorganic Chemistry | Year: 2016

A high-yielding and facile synthesis for diphosphane monochalcogenides (1Ch (R)) and their constitutional isomers, diphosphanylchalcoganes (2Ch (R)), was developed, featuring a condensation reaction between chlorophosphanes (R2PCl) and sodium chalcogenides (Na2Ch, Ch = S, Se, (Te)). The optimized protocol selectively yields either 1Ch (R) (R2(Ch)PPR2) or 2Ch (R) (Ch(PR2)2) depending upon the steric demand of the substituents R. Reaction pathways consistent with the distinct reaction outcomes are proposed. The application of 1Ch (R) and 2Ch (R) as an interesting class of ligands is exemplarily demonstrated by the preparation of selected transition metal complexes. © 2016 American Chemical Society.


Beham G.,Know Center GmbH | Kump B.,Know Center GmbH | Ley T.,Know Center GmbH | Ley T.,University of Graz | And 2 more authors.
Procedia Computer Science | Year: 2010

According to studies into learning at work, interpersonal help seeking is the most important strategy of how people acquire knowledge at their workplaces. Finding knowledgeable persons, however, can often be difficult for several reasons. Expert finding systems can support the process of identifying knowledgeable colleagues thus facilitating communication and collaboration within an organization. In order to provide the expert finding functionality, an underlying user model is needed that represents the characteristics of each individual user. In our article we discuss requirements for user models for the workintegrated learning (WIL) situation. Then, we present the APOSDLE People Recommender Service which is based on an underlying domain model, and on the APOSDLE User Model. We describe the APOSDLE People Recommender Service on the basis of the Intuitive Domain Model of expert finding systems, and explain how this service can support interpersonal help seeking at workplaces.


Seidl-Seiboth V.,Vienna University of Technology | Zach S.,Vienna University of Technology | Frischmann A.,Vienna University of Technology | Spadiut O.,Vienna University of Technology | And 8 more authors.
FEBS Journal | Year: 2013

LysM motifs are carbohydrate-binding modules found in prokaryotes and eukaryotes. They have general N-acetylglucosamine binding properties and therefore bind to chitin and related carbohydrates. In plants, plasma-membrane-bound proteins containing LysM motifs are involved in plant defence responses, but also in symbiotic interactions between plants and microorganisms. Filamentous fungi secrete LysM proteins that contain several LysM motifs but no enzymatic modules. In plant pathogenic fungi, for LysM proteins roles in dampening of plant defence responses and protection from plant chitinases were shown. In this study, the carbohydrate-binding specificities and biological function of the LysM protein TAL6 from the plant-beneficial fungus Trichoderma atroviride were investigated. TAL6 contains seven LysM motifs and the sequences of its LysM motifs are very different from other fungal LysM proteins investigated so far. The results showed that TAL6 bound to some forms of polymeric chitin, but not to chito-oligosaccharides. Further, no binding to fungal cell wall preparations was detected. Despite these rather weak carbohydrate-binding properties, a strong inhibitory effect of TAL6 on spore germination was found. TAL6 was shown to specifically inhibit germination of Trichoderma spp., but interestingly not of other fungi. Thus, this protein is involved in self-signalling processes during fungal growth rather than fungal-plant interactions. These data expand the functional repertoire of fungal LysM proteins beyond effectors in plant defence responses and show that fungal LysM proteins are also involved in the self-regulation of fungal growth and development. LysM motifs have general chitin-binding properties and fungal LysM proteins are involved in fungal-plant interactions. We investigated the LysM protein TAL6 from Trichoderma atroviride. The results showed that TAL6 inhibits spore germination of Trichoderma species, but interestingly not of other fungi. This expands the functions of fungal LysM proteins to roles in the self-regulation of fungal growth and development © 2013 FEBS.


Rode M.,University of Graz | Kellerer-Pirklbauer A.,University of Graz | Kellerer-Pirklbauer A.,Graz University of Technology
Holocene | Year: 2012

Schmidt-hammer rebound values (R-values) enable relative-age dating of landforms, with R-values relating to degree of weathering and therefore length of exposure. This method - recently termed as Schmidt-hammer exposure-age dating (SHD) - was applied to date five rock glaciers (size range, 0.01-0.12 km2) and one recent rockfall deposit at the study area Schöderkogel-Eisenhut, in the Schladminger Tauern Range (14°03′E, 47°15′N), Austria. The rock glaciers consist of gneiss or high metamorphic series of mica-schist that are comparable in their R-values. Four of them are relict (permafrost absent) and one is intact (containing patches of permafrost). On each of the five rock glaciers, SHD was carried out at 4-6 sites (50 measurements per site) along a longitudinal transect from the frontal ridge to the root zone. Results at all five rock glaciers are generally consistent with each other sharing statistically significant R-values along transects. The range between the highest and the lowest mean R-value at each of the five rock glaciers is 9.9-5.2. Using rock glacier length and surface velocity data from nearby sites, the rock glacier development must have lasted for several thousand years. Furthermore, by using SHD results from rock glaciers of known age from other sites in the region with comparable geology, approximate surface ages of 6.7-11.4 ka were estimated. This indicates long formation periods for all five rock glaciers. Our results suggest that many of the 1300 relict rock glaciers in central and eastern Austria were formed over a long period during the Lateglacial and Holocene period. © The Author(s) 2011.


Zach C.,ETH Zurich | Klopschitz M.,Graz University of Technology | Pollefeys M.,ETH Zurich
Proceedings of the IEEE Computer Society Conference on Computer Vision and Pattern Recognition | Year: 2010

Repetitive and ambiguous visual structures in general pose a severe problem in many computer vision applications. Identification of incorrect geometric relations between images solely based on low level features is not always possible, and a more global reasoning approach about the consistency of the estimated relations is required. We propose to utilize the typically observed redundancy in the hypothesized relations for such reasoning, and focus on the graph structure induced by those relations. Chaining the (reversible) transformations over cycles in this graph allows to build suitable statistics for identifying inconsistent loops in the graph. This data provides indirect evidence for conflicting visual relations. Inferring the set of likely false positive geometric relations from these non-local observations is formulated in a Bayesian framework. We demonstrate the utility of the proposed method in several applications, most prominently the computation of structure and motion from images. ©2010 IEEE.


Hajnal I.,Austrian Center of Industrial Biotechnology | Hajnal I.,Technical University of Delft | Lyskowski A.,Austrian Center of Industrial Biotechnology | Hanefeld U.,Technical University of Delft | And 5 more authors.
FEBS Journal | Year: 2013

Hydroxynitrile lyases (HNLs), which catalyse the decomposition of cyanohydrins, are found mainly in plants. In vitro, they are able to catalyse the synthesis of enantiopure cyanohydrins, which are versatile building blocks in the chemical industry. Recently, HNLs have also been discovered in bacteria. Here, we report on the detailed biochemical and structural characterization of a hydroxynitrile lyase from Granulicella tundricola (GtHNL), which was successfully heterologously expressed in Escherichia coli. The crystal structure was solved at a crystallographic resolution of 2.5 Å and exhibits a cupin fold. As GtHNL does not show any sequence or structural similarity to any other HNL and does not contain conserved motifs typical of HNLs, cupins represent a new class of HNLs. GtHNL is metal-dependent, as confirmed by inductively coupled plasma/optical emission spectroscopy, and in the crystal structure, manganese is bound to three histidine and one glutamine residue. GtHNL displayed a specific activity of 1.74 U·mg-1 at pH 6 with (R)-mandelonitrile, and synthesized (R)-mandelonitrile with 90% enantiomeric excess at 80% conversion using 0.5 m benzaldehyde in a biphasic reaction system with methyl tertiary butyl ether. Hydroxynitrile lyases are used in biocatalysis to catalyse the synthesis of enantiopure cyanohydrins, which are versatile building blocks in chemical industry. We report on the detailed biochemical and structural characterisation of a metal-dependent HNL from Granulicella tundricola, which was successfully heterologously expressed in E. coli. The crystal structure was solved at a crystallographic resolution of 2.5 Å and exhibits a cupin fold. © 2013 FEBS.


Falkner A.,Graz University of Technology | Felfernig A.,Siemens AG | Haag A.,SAP
AI Magazine | Year: 2011

State-of-the-art recommender systems support users in the selection of items from a predefined assortment (for example, movies, books, and songs). In contrast to an explicit definition of each individual item, configurable products such as computers, financial service portfolios, and cars are repre sented in the form of a configuration knowledge base that de - scribes the properties of allowed instances. Although the knowledge representation used is different compared to nonconfi gurable products, the decision support requirements remain the same: users have to be supported in finding a solution that fits their wishes and needs. In this article we show how recommendation technologies can be applied for supporting the configuration of products. In addition to existing approaches we discuss relevant issues for future research. Copyright © 2011, Association for the Advancement of Artificial Intelligence. All rights reserved.


Shit S.,Jadavpur University | Shit S.,Jalpaiguri Government Engineering College | Marschner C.,Graz University of Technology | Mitra S.,Jadavpur University
Acta Chimica Slovenica | Year: 2016

A new mixed ligand copper(II) complex, [Cu(2,4-pydc)(pic)(H2O)] · H2O (1) (where 2,4-pydc = pyridine-2,4-dicarboxylate, pic = 2-picolylamine) has been synthesized and characterized by elemental analysis, FT-IR and UV-Vis spectroscopic and thermogravimetric methods. Single crystal X-ray diffraction analysis reveals that copper(II) atom in the title complex adopts distorted square-pyramidal geometry. Structural characterization also reveals that interplay of O-H·O, N-H···O, C-H···O, and C-H··· π interactions between lattice and coordinated water and ligands significantly contribute to the crystal packing leading to the formation and strengthening of three dimensional supramolecular assembly. Hirshfeld surface analysis employing 3D molecular surface contours and 2D fingerprint plots have been used to analyze intermolecular interactions present in the solid state of the crystal.


Mowlaee P.,Graz University of Technology | Saeidi R.,University of Eastern Finland
2014 14th International Workshop on Acoustic Signal Enhancement, IWAENC 2014 | Year: 2014

Previous single-channel speech enhancement algorithms often employ noisy phase while reconstructing the enhanced signal. In this paper, we propose novel phase estimation methods by employing several temporal and spectral constraints imposed on the phase spectrum of speech signal. We pose the phase estimation problem as estimating the unknown clean speech phase at sinusoids observed in additive noise. To resolve the ambiguity in phase estimation problem, we introduce individual time-frequency constraints: group delay deviation, instantaneous frequency deviation, and relative phase shift. Through extensive simulations, the effectiveness of the proposed phase estimation methods in single-channel speech enhancement is demonstrated. Employing the estimated phase for signal reconstruction in medium-to-high SNRs leads to consistent improvement in perceived quality compared to when noisy phase is used. © 2014 IEEE.


Persson B.N.J.,Julich Research Center | Ganser C.,University of Leoben | Schmied F.,University of Leoben | Teichert C.,University of Leoben | And 3 more authors.
Journal of Physics Condensed Matter | Year: 2013

The surface topography of paper fibers is studied using atomic force microscopy (AFM), and thus the surface roughness power spectrum is obtained. Using AFM we have performed indentation experiments and measured the effective elastic modulus and the penetration hardness as a function of humidity. The influence of water capillary adhesion on the fiber-fiber binding strength is studied. Cellulose fibers can absorb a significant amount of water, resulting in swelling and a strong reduction in the elastic modulus and the penetration hardness. This will lead to closer contact between the fibers during the drying process (the capillary bridges pull the fibers into closer contact without storing up a lot of elastic energy at the contacting interface). In order for the contact to remain good in the dry state, plastic flow must occur (in the wet state) so that the dry surface profiles conform to each other (forming a key-and-lock type of contact). © 2013 IOP Publishing Ltd.


Narodoslawsky M.,Graz University of Technology
Computer Aided Chemical Engineering | Year: 2014

The European Federation of Chemical Engineering (EFCE) is taking up the challenge of sustainable development by installing a special Sustainability Section to discuss the wide ranging implications of this development concept. Sustainable development will require a thorough re-structuring of chemical industry within the next decades and a fundamental re-orientation of the way chemical engineers pursue their research, technological development and design work as well. This poses new and formidable challenges to the European CAPE community. Three challenges require new CAPE solutions in particular. •The integration of life cycle assessment into chemical engineering design;•A change towards renewable resources for energy provision and raw materials for industrial processes;•A systemic approach to integrating chemical industry sustainably into supply chains while providing energy services to society at the same time. The re-orientation of chemical engineering research and design is already visible in the efforts of young chemical engineering researchers. Interdisciplinary research as well as tackling the tasks linked to the new role of chemical engineering within sustainable development is more and more defining the work of young chemical engineers. This has been particularly visible in the CAPE Forum 2013, that brought together an interdisciplinary group of researchers from 13 European countries to discuss these challenges of sustainable development and that fostered the discourse between young researchers and experienced scientists and practitioners. The paper will link the results of the 32 contributions to the CAPE Forum 2013 and the on-going initiatives in the Sustainability Section of the EFCE to generate a picture of the future role of the CAPE community with regard to sustainable development. © 2014 Elsevier B.V.


Bo P.,University of Hong Kong | Bo P.,Vienna University of Technology | Pottmann H.,Vienna University of Technology | Kilian M.,Vienna University of Technology | And 2 more authors.
ACM Transactions on Graphics | Year: 2011

The most important guiding principle in computational methods for freeform architecture is the balance between cost efficiency on the one hand, and adherence to the design intent on the other. Key issues are the simplicity of supporting and connecting elements as well as repetition of costly parts. This paper proposes so-called circular arc structures as a means to faithfully realize freeform designs without giving up smooth appearance. In contrast to non-smooth meshes with straight edges where geometric complexity is concentrated in the nodes, we stay with smooth surfaces and rather distribute complexity in a uniform way by allowing edges in the shape of circular arcs. We are able to achieve the simplest possible shape of nodes without interfering with known panel optimization algorithms. We study remarkable special cases of circular arc structures which possess simple supporting elements or repetitive edges, we present the first global approximation method for principal patches, and we show an extension to volumetric structures for truly threedimensional designs. © 2011 ACM.


Trattner C.,Graz University of Technology
Journal of Computing and Information Technology | Year: 2011

Recent research has shown that the navigability of tagging systems leaves much to be desired. In general, it was observed that tagging systems are not navigable if the resource lists of the tagging system are limited to a certain factor k. Hence, in this paper a novel resource list generation approach is introduced that addresses this issue. The proposed approach is based on a hierarchical network model. The paper shows through a number of experiments based on a tagging dataset from a large online encyclopedia system called Austria-Forum, that the new algorithm is able to create tag network structures that are navigable in an efficient manner. Contrary to previous work, the method featured in this paper is completely generic, i.e. the introduced resource list generation approach could be used to improve the navigability of any tagging system. This work is relevant for researchers interested in navigability of emergent hypertext structures and for engineers seeking to improve the navigability of tagging systems.


Schnizer P.,Helmholtz Center for Heavy Ion Research | Fischer E.,Helmholtz Center for Heavy Ion Research | Schnizer B.,Graz University of Technology
IPAC 2012 - International Particle Accelerator Conference 2012 | Year: 2012

Machines with high currents and small apertures, as used for SIS100 of the FAIR project, require a sincere understanding of the resonances excited by the magnetic field distortions; typically performed by tracking codes. These codes model the field errors using a Taylor Series approximation of the field quality at the track of the ideal particle. The path of the particle within the elliptic aperture of the dipole is curved; thus the standard approach of using plane circular multipoles fails to model the real symmetry of the magnetic field, an important feature of effective field description for beam loss calculations. Therefore toroidal elliptic multipoles were developed which allow describing the magnetic field concisely in an elliptic vacuum chamber in curved dipoles and quadrupoles. Copyright © 2012 by IEEE.


Aichhorn M.,Graz University of Technology | Aichhorn M.,Ecole Polytechnique - Palaiseau | Pourovskii L.,Ecole Polytechnique - Palaiseau | Pourovskii L.,Linkoping University | And 3 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

We present calculations of structural and magnetic properties of the iron-pnictide superconductor LaFeAsO including electron-electron correlations. For this purpose we apply a fully charge self-consistent combination of density-functional theory with the dynamical mean-field theory, allowing for the calculation of total energies. We find that the inclusion of correlation effects gives a good agreement of the arsenic z position with experimental data even in the paramagnetic (high-temperature) phase. Going to low temperatures, we study the formation of the ordered moment in the striped spin-density-wave phase, yielding an ordered moment of about 0.60μB, again in good agreement with experiments. This shows that the inclusion of correlation effects improves both structural and magnetic properties of LaFeAsO at the same time. © 2011 American Physical Society.


Schubert W.,Graz University of Technology
Harmonising Rock Engineering and the Environment - Proceedings of the 12th ISRM International Congress on Rock Mechanics | Year: 2012

Accidents, cost- and time overruns at tunnel projects are still rather common. It appears that design and construction procedures still do not comply with the requirements of an up to date engineering approach. Too often dominant behaviors during the design process are ignored or the models simplified in a way that critical mechanisms cannot be detected. To improve the situation, design and construction processes need to be adopted, which focus on the inherent risks of tunneling. The paper presents such an approach, which has been used successfully over the last decade. © 2012 Taylor & Francis Group, London.


Korak T.,Graz University of Technology | Plos T.,NXP Semiconductors
Proceedings - 9th International Conference on Availability, Reliability and Security, ARES 2014 | Year: 2014

Security-relevant applications applying contactless communication technologies based on radio-frequency identification (RFID) need to be robust against side-channel analysis (SCA) attacks. This work compares two measurement approaches for evaluating the robustness of RFID devices against SCA attacks: Analogue demodulation and resolution optimization of the oscilloscope. Several distances for measuring the side-channel information have been evaluated showing that above a specific distance the resolution optimization outperforms the analogue pre-processing. By applying a pre-processing step, the results can further be improved. With an appropriate measurement setup the effort for a security evaluation can be decreased, further leading to faster time-to-market and reduced development costs. © 2014 IEEE.


Meng S.,Peking University | Arbab F.,CWI | Aichernig B.K.,Graz University of Technology | Atefnoaei L.,CWI | And 2 more authors.
Science of Computer Programming | Year: 2012

Over the past years, the need for high-confidence coordination mechanisms has intensified as new technologies have appeared for the development of service-oriented applications, making formalization of coordination mechanisms critical. Unifying Theories of Programming (UTP) provide a formal semantic foundation not only for programming languages but also for various expressive specification languages. A key concept in UTP is design: the familiar pre/post-condition pair that describes a contract. In this paper we use UTP to formalize Reo connectors, whereby connectors are interpreted as designs in UTP. This model can be used as a semantic foundation for proving properties of connectors, such as equivalence and refinement relations between connectors. Furthermore, it can be used as a reference document for developing tool support for Reo, such as test case generators. A fault-based method to generate test cases for component connectors from specifications is also provided in this paper. For connectors, faults are caused by possible errors during the development process, such as wrongly used channels, missing or redundant subcircuits, or circuits with wrongly constructed topology. We give test cases and connectors a unifying formal semantics by using the notion of design in UTP, and generate test cases by solving constraints obtained from a specification and a faulty implementation. A prototype serves to demonstrate the automatization of the approach. © 2010 Elsevier B.V. All rights reserved.


Schuss C.,University of Oulu | Gall H.,Ams Ag Inc. | Eberhart K.,Ams Ag Inc. | Illko H.,Ams Ag Inc. | Eichberger B.,Graz University of Technology
Conference Record - IEEE Instrumentation and Measurement Technology Conference | Year: 2014

In this paper we discuss the alignment and system structures of photovoltaics on the roof of electric vehicles (EVs) and hybrid electric vehicles (HEVs). We focus on the interconnection of PV cells. In general, the position of photovoltaics on the roof of automobiles is crucial and has a strong impact on the photovoltaic (PV) output behaviour, in particular their output power level. We present strategies which allow the adaption of system structures according to changes in environmental conditions. As a result, we increase output performance levels by changing the interconnection of photovoltaics dynamically. © 2014 IEEE.


Steinbach O.,Graz University of Technology
Computational Mechanics | Year: 2013

In this paper we discuss the use of single and double layer boundary integral equations for the numerical solution of linear elasticity problems with boundary conditions of mixed type, and the one-equation coupling of finite and boundary element methods to solve a free space transmission problem. In particular we present a sufficient and necessary condition which ensures stability of the coupled approach for any choice of finite and boundary elements. These results justify the coupling of collocation and Galerkin one-equation boundary element methods with finite elements as used in many engineering and industrial applications. Hence one may avoid the use of the symmetric formulation of boundary integral equations, which is, although well established from a mathematical point of view and also used in some engineering applications, not so much accepted in particular in industrial applications. © 2012 Springer-Verlag.


Haber T.,Ams Ag Inc. | Gspan C.,Graz University of Technology
Conference Proceedings from the International Symposium for Testing and Failure Analysis | Year: 2014

This study investigated the origin of detrimental high ohmic behavior of contacts by means of analytical electron microscopy. The root cause for the high resistivity could be identified as delamination of the contact bottom in the nanometer range. Based on the results, we were able to establish a method to identify thin oxide layers using analytical methods without being able to spatially resolve them in a combined focused ion beam instrument and scanning electron microscope. Copyright © 2014 ASM International® All rights reserved.


Schuss C.,University of Oulu | Eichberger B.,Graz University of Technology | Rahkonen T.,University of Oulu
Conference Record - IEEE Instrumentation and Measurement Technology Conference | Year: 2014

In this paper we present strategies that potentially improve the output performance of interconnections of low-cost, low-power photovoltaic (PV) modules. These types of photovoltaics are of interest in particular for consumer electronics. In general, output power levels of photovoltaics vary depending on tolerance limits of PV manufacturers. We concentrated on influences on the characteristic I-V (Current-Voltage) curve and used the fill factor (FF) to describe the slope of the I-V curve. We investigated influences on maximum power point tracking (MPPT) techniques. We improved output power levels by applying evolutionary algorithms and pairing PV modules systematically. © 2014 IEEE.


Krakhofer S.,City University of Hong Kong | Kaftan M.,Graz University of Technology
CAADRIA 2015 - 20th International Conference on Computer-Aided Architectural Design Research in Asia: Emerging Experiences in the Past, Present and Future of Digital Architecture | Year: 2015

Augmented reality has come a long way and experienced a paradigm shift in 1999 when the ARToolKit was released as open source. The nature of interaction between the physical world and the virtual-world has changed forever. Fortunately for the AECO industry, the transition from traditional Computer Aided Design to virtual building design phrased as Building Information Modeling has created a tremendous potential to adopt Augmented Reality. The presented research is situated in the early design stage of project inception and focuses on supporting informed collective decision-making, characterized by a dynamic back and forth analytical process generating large amounts of data. Facilitation aspects, such as data-collection, storage and access to enable comparability and evaluation are crucial for collective decision-making. The current research has addressed these aspects by means of data accessibility, visualization and presentation. At the core of the project is a custom developed Augmented Reality framework that enables data interaction within the design model. In order to serve as a collaborative decision support engine, the framework also allows multiple models and their datasets to be displayed and exercised simultaneously. The paper demonstrates in the case study the successful application of the AR tool during collaborative design decision meetings. © 2015 All rights reserved and published by The Association for Computer-Aided Architectural Design Research in Asia (CAADRIA), Hong Kong.


Gappmair W.,Graz University of Technology | Ginesi A.,European Space Agency
International Journal of Satellite Communications and Networking | Year: 2016

Data throughput and availability of multibeam satellite links are limited by interference problems, in particular when the design is determined by an aggressive reuse of frequency bands. Usually, this is mitigated by appropriately selected techniques like precoding or multi-user detection. Before such methods are applicable, however, the most important transmission parameters have to be recovered successfully even under very challenging conditions caused by (full) frequency reuse. The detailed analysis of the log-likelihood function characterizing the multibeam scenario shows that a beamwise decoupling of the estimation task is possible, if the following three conditions are met: (i) alignment of all frequency offsets; (ii) symbol synchronicity; (iii) orthogonal synchronization sequences. Based on these assumptions, it turns out that the modified Cramer-Rao lower bound (MCRLB) for carrier frequency and phase, symbol timing and signal amplitude is the same, no matter whether we are dealing with a single or a multiple beam situation. Furthermore, because a maximum likelihood framework for parameter estimation is not available in closed form, we introduce a sub-optimal concept of low-complex algorithms. Finally, it is verified by simulation results that the jitter variance of each recovery scheme is close to the related MCRLB, when the decoupling conditions are satisfied. © 2016 John Wiley & Sons, Ltd.


Adhikary J.,University of Calcutta | Chakraborty P.,University of Calcutta | Chattopadhyay T.,Panchakot Mahavidyalaya | Prasad R.,Banaras Hindu University | And 5 more authors.
Polyhedron | Year: 2015

Two new mononuclear Ni(II) complexes, namely [Ni(HL)(SCN)2(H2O)] (1) and [Ni(HL)(SCN)2(4,4′-bipy)] (2) [HL = 2-[(2-piperazin-1-yl-ethylimono)-methyl]phenol] have been synthesized and structurally characterized. The uncoordinated nitrogen atom of the piperazine moiety is protonated to provide electrical neutrality to the system. The configuration of the isothiocyanato ligands is different in the two complexes, cis located in 1 and trans in complex 2. The change of configuration of the isothiocyanato groups on addition of the neutral spacer 4,4-bipyridine to complex 1 has been monitored by conductometric and FTIR spectral studies and the most probable mechanistic pathway has been proposed. DFT calculations have been performed and the outcome corroborates well with the experimental facts. The anticancer activity of the two Ni(II) complexes has been evaluated in human cervical (HeLa) cancer and breast cancer (MCF-7) cell lines. The cytotoxic effects of these complexes were determined by an MTT assay. The fluorescent intensity obtained in HeLa cells reveals the generation of ROS by the complexes using DCFH-DA (2,7-dichlorofluorescein diacetate) dye. The apoptotic cell death was determined by fluorescent staining with acridine orange and ethidium bromide, which confirmed the presence of apoptotic cells. Further, flow cytometry analysis was done, suggesting an arrest of the cell cycle in the S phase of the HeLa cells. Although a detailed molecular mechanism for the anticancer activity of the two complexes was not ascertained, the experimental results suggest that both complexes are effective anticancer agents, with complex 2 seeming to be more promising. The result also indicates that the apoptotic cell death in the cancer cell might be triggered by the process of ROS generation with the complexes. Thermo gravimetric analysis of two complexes hints that NiO particles are the final product after decomposition of the complexes at 600 °C. © 2015 Elsevier Ltd. All rights reserved.


Unterwieser H.,Holz.bau Forschungs GmbH | Schickhofer G.,Graz University of Technology
European Journal of Wood and Wood Products | Year: 2011

This study comprises the analysis of the influence of the moisture content of wood on the dynamic properties-sound velocity and dynamic MOE (considering the density)-of green and dry sawn timber. The main objective was to find applicable functions or factors for the adjustment of the determined properties on the reference condition (moisture content u=12%) for the moisture content range below and above fiber saturation. Therefore, two dynamic measurement methods-measurement of the natural frequency and ultrasonic runtime-were considered. Possible differences in the results, pros and cons of both methods should be identified on the one hand. On the other hand, the applicability of already published moisture adjustments to the given data of both methods should be proved. © 2010 Springer-Verlag.


Grandi G.,University of Bologna | Loncarski J.,University of Bologna | Seebacher R.,Graz University of Technology
2012 IEEE International Energy Conference and Exhibition, ENERGYCON 2012 | Year: 2012

Inverter dead-time distortion in output voltages have been widely investigated in the past for three-phase PWM voltage source inverters. Also, there have been some studies about multi-phase inverters with reference to multi-phase drives. Usually, almost sinusoidal output currents are considered, with a single zero crossing for every half fundamental period. High output current ripple introduces multiple zero crossing, leading to modified output voltage distortions. In this paper the effect of the output current ripple has been taken into account, in the case of carrier-based PWM techniques when no any dead-time compensation technique is applied. In particular, the harmonic spectrum of the output voltage distortion has been evaluated on the basis of the multiple zero crossing time interval of output currents. In case of relevant current ripple it is verified a relevant deviation of output voltage harmonics in comparison to the case of almost sinusoidal currents. Theoretical analysis has shown that particular low-order harmonics are affected by the current ripple amplitude, and simulation results confirm the developed analytical approach. © 2012 IEEE.


Schickling T.,University of Marburg | Bunemann J.,University of Marburg | Gebhard F.,University of Marburg | Boeri L.,Graz University of Technology
Physical Review B - Condensed Matter and Materials Physics | Year: 2016

We use the Gutzwiller density-functional theory to calculate ground-state properties and band structures of iron in its body-centered-cubic (bcc) and hexagonal-close-packed (hcp) phases. For a Hubbard interaction U=9eV and Hund's-rule coupling J=0.54eV, we reproduce the lattice parameter, magnetic moment, and bulk modulus of bcc iron. For these parameters, bcc is the ground-state lattice structure at ambient pressure up to a pressure of pc=41GPa where a transition to the nonmagnetic hcp structure is predicted, in qualitative agreement with experiment (pcexp=10,...,15GPa). The calculated band structure for bcc iron is in good agreement with ARPES measurements. The agreement improves when we perturbatively include the spin-orbit coupling. © 2016 American Physical Society.


Samson A.C.,Stanford University | Lackner H.K.,Medical University of Graz | Lackner H.K.,Graz University of Technology | Weiss E.M.,University of Graz | Papousek I.,University of Graz
Journal of Behavior Therapy and Experimental Psychiatry | Year: 2012

Background and objectives: The present study examined the relationship between social anxiety and the appreciation of specific types of humor. It was expected that social anxiety would hinder the enjoyment of jokes particularly if the resolution of incongruity involves processing social cues and assessing the (false) mental states of others. Fifty-six participants rated three types of cartoons and a control condition for comprehensibility and funniness. Results: High degrees of social anxiety were associated with less enjoyment of cartoons that involved the interpretation of others' mental states (Theory of Mind), but not of semantic cartoons or visual puns. Furthermore, high social anxiety was related to longer response latencies of the funniness ratings, especially in the case of Theory of Mind cartoons. Limitations: A possible limitation is that the present study was conducted in individuals with social anxiety in the non-clinical range. Conclusions: The findings suggest that highly socially anxious people do not have a general humor processing deficit, but may feel threatened by tasks involving the mental states of others. The negative affect evoked by TOM humor may hinder the experience of funniness in highly socially anxious individuals, and it may also make it more difficult for them to rate their own amusement. © 2011 Elsevier Ltd. All rights reserved.


Huber A.,Graz University of Technology
Match | Year: 2011

Recently we introduced a nonlinear partial differential equation (nPDE) of the third order for the first time. This new model equation allows the extension of the Debye-HOckel Theory (DHT) in the sense of considering time dependence explicitly. This leads to a new formulation in the meaning of the known nonlinear Poisson-Boltzmann Equation (nPBE). The purpose of the present paper follows two intensions: Firstly we show how we can solve the new model equation by an alternative algebraic method without using any approximations and numerical methods. This covers the mathematical standpoint of view. Secondly we show how we can interpret classes of solutions in the sense of describing electrochemical situations. Here the functions of interest will be directly connected with the time-dependent potential. Using a special algebraic approach involving elliptic functions, classes of solutions result naturally especially those of periodic behaviour.


Lehner F.,Graz University of Technology
Journal of Combinatorial Theory. Series A | Year: 2011

Noncommutative invariant theory is a generalization of the classical invariant theory of the action of SL(2,C) on binary forms. The dimensions of the spaces of invariant noncommutative polynomials coincide with the numbers of certain noncrossing partitions. We give an elementary combinatorial explanation of this fact by constructing a noncrossing basis of the homogeneous components. Using the theory of free stochastic measures this provides a combinatorial proof of the Molien-Weyl formula in this setting. © 2010 Elsevier Inc.


Wriessnegger T.,Acib Austrian Center of Industrial Biotechnology | Pichler H.,Acib Austrian Center of Industrial Biotechnology | Pichler H.,Graz University of Technology
Progress in Lipid Research | Year: 2013

Terpenoids comprise various structures conferring versatile functions to eukaryotes, for example in the form of prenyl-anchors they attach proteins to membranes. The physiology of eukaryotic membranes is fine-tuned by another terpenoid class, namely sterols. Evidence is accumulating that numerous membrane proteins require specific sterol structural features for function. Moreover, sterols are intermediates in the synthesis of steroids serving as hormones in higher eukaryotes. Like steroids many compounds of the terpenoid family do not contribute to membrane architecture, but serve as signalling, protective or attractant/repellent molecules. Particularly plants have developed a plenitude of terpenoid biosynthetic routes branching off early in the sterol biosynthesis pathway and, thereby, forming one of the largest groups of naturally occurring organic compounds. Many of these aromatic and volatile molecules are interesting for industrial application ranging from foods to pharmaceuticals. Combining the fortunate situation that sterol biosynthesis is highly conserved in eukaryotes with the amenability of yeasts to genetic and metabolic engineering, basically all naturally occurring terpenoids might be produced involving yeasts. Such engineered yeasts are useful for the study of biological functions and molecular interactions of terpenoids as well as for the large-scale production of high-value compounds, which are unavailable in sufficient amounts from natural sources due to their low abundance. © 2013 Elsevier Ltd. All rights reserved.


Barton M.,King Abdullah University of Science and Technology | Shi L.,King Abdullah University of Science and Technology | Kilian M.,Evolute GmbH | Kilian M.,Vienna University of Technology | And 4 more authors.
Computer Graphics Forum | Year: 2013

We discuss the theory, discretization, and numerics of curves which are evolving such that part of their shape, or at least their curvature as a function of arc length, remains unchanged. The discretization of a curve as a smooth sequence of circular arcs is well suited for such purposes, and allows us to reduce evolution of curves to the evolution of a control point collection in a certain finite-dimensional shape space. We approach this evolution by a 2-step process: linearized evolution via optimized velocity fields, followed by optimization in order to exactly fulfill all geometric side conditions. We give applications to freeform architecture, including "rationalization" of a surface by congruent arcs, form finding and, most interestingly, non-static architecture. © 2013 The Author(s) Computer Graphics Forum © 2013 The Eurographics Association and Blackwell Publishing Ltd.


Klug L.,University of Graz | Tarazona P.,University of Gottingen | Gruber C.,Austrian Center of Industrial Biotechnology | Gruber C.,University of Natural Resources and Life Sciences, Vienna | And 12 more authors.
Biochimica et Biophysica Acta - Molecular and Cell Biology of Lipids | Year: 2014

The methylotrophic yeast Pichia pastoris is a popular yeast expression system for the production of heterologous proteins in biotechnology. Interestingly, cell organelles which play an important role in this process have so far been insufficiently investigated. For this reason, we started a systematic approach to isolate and characterize organelles from P. pastoris. In this study, we present a procedure to isolate microsomal membranes at high purity. These samples represent endoplasmic reticulum (ER) fractions which were subjected to molecular analysis of lipids and proteins. Organelle lipidomics included a detailed analysis of glycerophospholipids, fatty acids, sterols and sphingolipids. The microsomal proteome analyzed by mass spectrometry identified typical proteins of the ER known from other cell types, especially Saccharomyces cerevisiae, but also a number of unassigned gene products. The lipidome and proteome analysis of P. pastoris microsomes are prerequisite for a better understanding of functions of this organelle and for modifying this compartment for biotechnological applications. © 2013 Elsevier B.V.


Donoser M.,Graz University of Technology
BMVC 2013 - Electronic Proceedings of the British Machine Vision Conference 2013 | Year: 2013

In this paper we introduce an efficient, effective and scalable clustering method denoted as Replicator Graph Clustering. Our method takes measures of similarity between pairs of data points (i. e. an affinity matrix) as input and identifies a set of clusters and unique cluster assignments in a fully unsupervised manner, where the cluster granularity is adaptable by a single parameter. We provide clustering results in three subsequent steps: (a) diffusing affinities by finding personalized evolutionary stable strategies of non-cooperative games (b) building a mutual k-nearest neighbor graph representing the underlying manifold and (c) applying a graph based clustering strategy which identifies the final clusters. Individual steps have low computational complexity which leads to an efficient clustering method, scaling well with an increasing number of data points. Experimental evaluation demonstrates competitive performance to state-of-the-art in several application fields.


Ivanciu L.-N.,Technical University of Cluj Napoca | Soser P.,Graz University of Technology | Hintea S.,Technical University of Cluj Napoca
2013 21st Telecommunications Forum Telfor, TELFOR 2013 - Proceedings of Papers | Year: 2013

This paper presents the design and analysis of a sub-1 dB noise figure CMOS single-ended Low Noise Amplifier (LNA), in 0.35 μm technology. The LNA operates at 2.1 GHz, addressing the Wideband Code Division Multiple Access (WCDMA) standard. Simulations prove that the gain and input return loss satisfy the requirements of this standard, with a noise figure value way less than specified. Temperature, voltage supply and process variation sweeps prove the robustness of the design. © 2013 IEEE.


Jiang C.,KAUST | Wang J.,KAUST | Wallner J.,Graz University of Technology | Pottmann H.,KAUST | Pottmann H.,Vienna University of Technology
Computer Graphics Forum | Year: 2014

Motivated by requirements of freeform architecture, and inspired by the geometry of hexagonal combs in beehives, this paper addresses torsion-free structures aligned with hexagonal meshes. Since repetitive geometry is a very important contribution to the reduction of production costs, we study in detail "honeycomb structures", which are defined as torsion-free structures where the walls of cells meet at 120 degrees. Interestingly, the Gauss-Bonnet theorem is useful in deriving information on the global distribution of node axes in such honeycombs. This paper discusses the computation and modeling of honeycomb structures as well as applications, e.g. for shading systems, or for quad meshing. We consider this paper as a contribution to the wider topic of freeform patterns, polyhedral or otherwise. Such patterns require new approaches on the technical level, e.g. in the treatment of smoothness, but they also extend our view of what constitutes aesthetic freeform geometry. © 2014 The Eurographics Association and John Wiley & Sons Ltd.


Choi N.-S.,Ulsan National Institute of Science and Technology | Chen Z.,Argonne National Laboratory | Freunberger S.A.,University of St. Andrews | Freunberger S.A.,Graz University of Technology | And 7 more authors.
Angewandte Chemie - International Edition | Year: 2012

Energy-storage technologies, including electrical double-layer capacitors and rechargeable batteries, have attracted significant attention for applications in portable electronic devices, electric vehicles, bulk electricity storage at power stations, and "load leveling" of renewable sources, such as solar energy and wind power. Transforming lithium batteries and electric double-layer capacitors requires a step change in the science underpinning these devices, including the discovery of new materials, new electrochemistry, and an increased understanding of the processes on which the devices depend. The Review will consider some of the current scientific issues underpinning lithium batteries and electric double-layer capacitors. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Zamecnikova M.,Vienna University of Technology | Wieser A.,ETH Zurich | Woschitz H.,Graz University of Technology | Ressl C.,Vienna University of Technology
Journal of Applied Geodesy | Year: 2014

The uncertainty of electronic distance measurement to surfaces rather than to dedicated precisionre flectors (reflectorless EDM) is afected by the entire system comprising instrument, atmosphere and surface. The impact of the latter is significant for applications like geodetic monitoring, high-precision surface modelling or laser scanner self-calibration. Nevertheless, it has not yet received sufficient attention and is not well understood. We have carried out an experimental investigation of the impact of surface reflectivity on the distance measurements of a terrestrial laser scanner. The investigation helps to clarify (i)whether variations of reflectivity cause systematic deviations of reflectorless EDM, and (ii) if so, whether it is possible and worth modelling these deviations. The results show that differences in reflectivity may actually cause systematic deviations of a few mm with diffusely re- flecting surfaces and even more with directionally reflecting ones. Using abivariate quadratic polynomial we were able to approximate these deviations as a function of measured distance and measured signal strength alone. Using this approximation to predict corrections, the deviations of the measurements could be reduced by about 70% in our experiment.We conclude that there is a systematic effect of surface reflectivity (or equivalently received signal strength) on the distance measurement and that it is possible to model and predict this effect. Integration into laser scanner calibration models may be beneficial for high precision applications. The results may apply to a broad range of instruments, not only to the specific laser scanner used herein. © Walter de Gruyter Berlin/Boston 2014.


Hohenadler M.,University of Wurzburg | Aichhorn M.,Graz University of Technology | Schmidt S.,ETH Zurich | Pollet L.,ETH Zurich
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2011

An array of high-Q electromagnetic resonators coupled to qubits gives rise to the Jaynes-Cummings-Hubbard model describing a superfluid to Mott-insulator transition of lattice polaritons. From mean-field and strong-coupling expansions, the critical properties of the model are expected to be identical to the scalar Bose-Hubbard model. A recent Monte Carlo study of the superfluid density on the square lattice suggested that this does not hold for the fixed-density transition through the Mott lobe tip. Instead, mean-field behavior with a dynamical critical exponent z=2 was found. We perform large-scale quantum Monte Carlo simulations to investigate the critical behavior of the superfluid density and the compressibility. We find z=1 at the tip of the insulating lobe. Hence the transition falls in the three-dimensional XY universality class, analogous to the Bose-Hubbard model. © 2011 American Physical Society.


Kober S.E.,University of Graz | Wood G.,University of Graz | Kampl C.,University of Graz | Neuper C.,University of Graz | And 2 more authors.
Behavioural Brain Research | Year: 2014

The aim of the present study was to investigate functional reorganization of the occipital cortex for a mental navigation task in blind people. Eight completely blind adults and eight sighted matched controls performed a mental navigation task, in which they mentally imagined to walk along familiar routes of their hometown during a multi-channel EEG measurement. A motor imagery task was used as control condition. Furthermore, electrophysiological activation patterns during a resting measurement with open and closed eyes were compared between blind and sighted participants. During the resting measurement with open eyes, no differences in EEG power were observed between groups, whereas sighted participants showed higher alpha (8-12. Hz) activity at occipital sites compared to blind participants during an eyes-closed resting condition. During the mental navigation task, blind participants showed a stronger event-related desynchronization in the alpha band over the visual cortex compared to sighted controls indicating a stronger activation in this brain region in the blind. Furthermore, groups showed differences in functional brain connectivity between fronto-central and parietal-occipital brain networks during mental navigation indicating stronger visuo-spatial processing in sighted than in blind people during mental navigation. Differences in electrophysiological parameters between groups were specific for mental navigation since no group differences were observed during motor imagery. These results indicate that in the absence of vision the visual cortex takes over other functions such as spatial navigation. © 2014 Elsevier B.V.


Weber D.,TU Darmstadt | Mueller-Roemer J.,TU Darmstadt | Stork A.,TU Darmstadt | Fellner D.,TU Darmstadt | Fellner D.,Graz University of Technology
Computer Graphics Forum | Year: 2015

We present a novel multigrid scheme based on a cut-cell formulation on regular staggered grids which generates compatible systems of linear equations on all levels of the multigrid hierarchy. This geometrically motivated formulation is derived from a finite volume approach and exhibits an improved rate of convergence compared to previous methods. Existing fluid solvers with voxelized domains can directly benefit from this approach by only modifying the representation of the non-fluid domain. The necessary building blocks are fully parallelizable and can therefore benefit from multi-and many-core architectures. © 2015 The Author(s) Computer Graphics Forum © 2015 The Eurographics Association and John Wiley & Sons Ltd. Published by John Wiley & Sons Ltd.


Morandi O.,Graz University of Technology
Journal of Mathematical Physics | Year: 2012

A quantum corrected dynamical model for charged particles is derived. The corrections to the Newton motion are obtained within the Liouville formalism and are expressed by an effective nonlinear force. This effective force describes the non-local character of the quantum particles. The well posedness of the quantum-corrected problem is studied from the mathematical point of view. Existence and uniqueness of the solution are proved for a mollified version of the effective force. Numerical tests are performed and the range of validity of the model is investigated. © 2012 American Institute of Physics.


Kreiner C.,Graz University of Technology | Messnarz R.,ISCN LTD GesmbH | Riel A.,EMIRACLE Association | Ekert D.,ISCN LTD GesmbH | And 2 more authors.
Communications in Computer and Information Science | Year: 2013

This paper discusses (based on the EU project AQUA) how the core elements of three complementary approaches and standards can be integrated into one compact skill set with training and best practices to be applied. In this project experts from Automotive SPICE (ISO 15504), Functional Safety (ISO 26262) and Lean Six Sigma collaborate. In a first analysis the experts identified an architecture of core elements where all three approaches fit together and where a holistic view about improvement is needed. The Automotive Clusters from Austria and Slovenia are trial partners and will roll out this knowledge in pilot courses to the industry. Other Automotive Clusters showed interest and will join the trial phase. © Springer-Verlag Berlin Heidelberg 2013.


Reiweger I.,WSL Institute for Snow and Avalanche Research SLF | Mayer K.,WSL Institute for Snow and Avalanche Research SLF | Mayer K.,Graz University of Technology | Steiner K.,WSL Institute for Snow and Avalanche Research SLF | And 3 more authors.
Cold Regions Science and Technology | Year: 2015

Acoustic emissions (AE) are transient elastic waves produced by a sudden redistribution of stress in a material caused by changes in the internal structure. In other natural, heterogeneous materials monitoring AE has proven to be a valuable tool for stability estimation and failure prediction. After studying the characteristics of ultrasonic wave propagation in snow, we measured the acoustic emission signals during snow loading experiments in a cold laboratory. Using snow columns we found that most energy of an artificial acoustic signal was transmitted at 31. kHz. Best coupling to snow was achieved by attaching the AE sensors with silicone adhesive to thin aluminium plates which were then frozen to the snow. Localizing AE events during fracture of layered snow samples showed that the AE originated within the weakest layer, i.e. the relevant layer for snow failure. For finding an indication of imminent failure, we analysed the exponent β of the cumulative size-frequency distribution ('survival curve') of event energy. At the occurrence of instabilities, the β-curve deviated from steady behaviour and exhibited distinct 'drops', indicating that the power law behaviour of the distribution was not fulfilled anymore. Studying the temporal evolution of the exponent β might therefore provide useful information about snowpack stability also in the field-provided that the AE signals are not too strongly attenuated and can be detected in time before catastrophic failure occurs. © 2014 Elsevier B.V.


Glazyrin K.,University of Bayreuth | Glazyrin K.,Yale University | Pourovskii L.V.,Linkoping University | Pourovskii L.V.,Ecole Polytechnique - Palaiseau | And 18 more authors.
Physical Review Letters | Year: 2013

We discover that hcp phases of Fe and Fe0.9Ni0.1 undergo an electronic topological transition at pressures of about 40 GPa. This topological change of the Fermi surface manifests itself through anomalous behavior of the Debye sound velocity, c/a lattice parameter ratio, and Mössbauer center shift observed in our experiments. First-principles simulations within the dynamic mean field approach demonstrate that the transition is induced by many-electron effects. It is absent in one-electron calculations and represents a clear signature of correlation effects in hcp Fe. © 2013 American Physical Society.


Burke R.,DePaul University | Felfernig A.,Graz University of Technology | Goker M.H.,Salesforce
AI Magazine | Year: 2011

Recommender systems are tools for interacting with large and complex information spaces. They provide a personalized view of such spaces, prioritizing items likely to be of interest to the user. The field, christened in 1995, has grown enormously in the variety of problems addressed and techniques employed, as well as in its practical applications. Recommender systems research has incorporated a wide variety of artificial intelligence techniques including machine learning, data mining, user modeling, case-based reasoning, and constraint satisfaction, among others. Personalized recommendations are an important part of many online ecommerce applications such as Amazon.com, Netflix, and Pandora. This wealth of practical application experience has provided inspiration to researchers to extend the reach of recommender systems into new and challenging areas. The purpose of the articles in this special issue is to take stock of the current landscape of recommender systems research and identify directions the field is now taking. This article provides an overview of the current state of the field and introduces the various articles in the special issue. Copyright © 2011, Association for the Advancement of Artificial Intelligence. All rights reserved.


Amann F.,ETH Zurich | Button E.A.,ETH Zurich | Blumel M.,Graz University of Technology | Thony R.,ETH Zurich
Rock Mechanics in Civil and Environmental Engineering - Proceedings of the European Rock Mechanics Symposium, EUROCK 2010 | Year: 2010

Opalinus Clay is considered to be a potential rock mass for the disposal of high level nuclear waste in Switzerland. This relatively weak over-consolidated clay shale has several benefiting characteristics, like low permeability and the potential for self-sealing that make it a first priority candidate as a host formation in Switzerland. However, the low strength of the anisotropic rock and the associated ground behavior is apparent and meaningful for both, the constructability and the long term integrity of the disposal site. Observations made during a mine-by project in the Mont Terri Underground Rock Laboratory showed brittle rock mass behavior. In order to understand the observed failure mechanisms a detailed laboratory investigation has been initiated comprising servo-controlled direct shear and unconfined compressive strength tests. © 2010 Taylor & Francis Group.


Sironi A.,Ecole Polytechnique Federale de Lausanne | Lepetit V.,Ecole Polytechnique Federale de Lausanne | Lepetit V.,Graz University of Technology | Fua P.,Ecole Polytechnique Federale de Lausanne
Proceedings of the IEEE International Conference on Computer Vision | Year: 2016

Detection of elongated structures in 2D images and 3D image stacks is a critical prerequisite in many applications and Machine Learning-based approaches have recently been shown to deliver superior performance. However, these methods essentially classify individual locations and do not explicitly model the strong relationship that exists between neighboring ones. As a result, isolated erroneous responses, discontinuities, and topological errors are present in the resulting score maps. We solve this problem by projecting patches of the score map to their nearest neighbors in a set of ground truth training patches. Our algorithm induces global spatial consistency on the classifier score map and returns results that are provably geometrically consistent. We apply our algorithm to challenging datasets in four different domains and show that it compares favorably to state-of-the-art methods. © 2015 IEEE.