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Showing papers by "Johannes Kepler University of Linz published in 2013"


Journal ArticleDOI
25 Jul 2013-Nature
TL;DR: In this paper, the authors present a platform that makes electronics both virtually unbreakable and imperceptible on polyimide polysilicon elastomers, which can be operated at high temperatures and in aqueous environments.
Abstract: Electronic devices have advanced from their heavy, bulky origins to become smart, mobile appliances. Nevertheless, they remain rigid, which precludes their intimate integration into everyday life. Flexible, textile and stretchable electronics are emerging research areas and may yield mainstream technologies. Rollable and unbreakable backplanes with amorphous silicon field-effect transistors on steel substrates only 3 μm thick have been demonstrated. On polymer substrates, bending radii of 0.1 mm have been achieved in flexible electronic devices. Concurrently, the need for compliant electronics that can not only be flexed but also conform to three-dimensional shapes has emerged. Approaches include the transfer of ultrathin polyimide layers encapsulating silicon CMOS circuits onto pre-stretched elastomers, the use of conductive elastomers integrated with organic field-effect transistors (OFETs) on polyimide islands, and fabrication of OFETs and gold interconnects on elastic substrates to realize pressure, temperature and optical sensors. Here we present a platform that makes electronics both virtually unbreakable and imperceptible. Fabricated directly on ultrathin (1 μm) polymer foils, our electronic circuits are light (3 g m(-2)) and ultraflexible and conform to their ambient, dynamic environment. Organic transistors with an ultra-dense oxide gate dielectric a few nanometres thick formed at room temperature enable sophisticated large-area electronic foils with unprecedented mechanical and environmental stability: they withstand repeated bending to radii of 5 μm and less, can be crumpled like paper, accommodate stretching up to 230% on prestrained elastomers, and can be operated at high temperatures and in aqueous environments. Because manufacturing costs of organic electronics are potentially low, imperceptible electronic foils may be as common in the future as plastic wrap is today. Applications include matrix-addressed tactile sensor foils for health care and monitoring, thin-film heaters, temperature and infrared sensors, displays, and organic solar cells.

2,062 citations


Journal ArticleDOI
TL;DR: The basic working principles and the state of the art device design of bulk heterojunction solar cells are reviewed and the importance of high power conversion efficiencies for the commercial exploitation is outlined and different efficiency models for bulk heterovoltaic cells are discussed.

923 citations


Journal ArticleDOI
TL;DR: In this article, an international review of numerous power-to-gas pilot plants that have either already been realized or are being planned is presented, which provides information about their installed components and capacities as well as operating experience that has been had with them.

916 citations


Journal ArticleDOI
TL;DR: In this paper, trathin sheets of polymer LEDs that emit light even when being crumpled or stretched have been realized, and they could prove useful for integration with textiles.
Abstract: Ultrathin sheets of polymer LEDs that emit light even when being crumpled or stretched have been realized The 2-μm-thick devices emit red or orange light with a sufficiently high brightness for indoor applications, and they could prove useful for integration with textiles

795 citations


Journal ArticleDOI
TL;DR: In this article, a CMOS-compatible photodetector based on graphene with multi-gigahertz operation ranging from the O-to U-band of telecommunication bands is demonstrated, highlighting the promise of graphene as a new material for integrated photonics.
Abstract: A CMOS-compatible photodetector based on graphene with multi-gigahertz operation ranging from the O- to U-band of telecommunication bands is demonstrated, highlighting the promise of graphene as a new material for integrated photonics.

675 citations


Journal ArticleDOI
TL;DR: In this paper, the authors conducted potentiodynamic measurements with iron electrodes colonized by sulfate-reducing bacteria (SRB) and found that the colonizing bacteria significantly reduced current stimulation, thus confirming biological catalysis rather than an abiotic cathodic effect of FeS.

375 citations


Journal ArticleDOI
TL;DR: This short review article focuses primarily on organic and bio-organic electronic and optoelectronic systems derived from or inspired by nature, and outlines the complex charge transport and photo-physics which control their behaviour.
Abstract: Inorganic semiconductors permeate virtually every sphere of modern human existence. Micro-fabricated memory elements, processors, sensors, circuit elements, lasers, displays, detectors, etc are ubiquitous. However, the dawn of the 21st century has brought with it immense new challenges, and indeed opportunities—some of which require a paradigm shift in the way we think about resource use and disposal, which in turn directly impacts our ongoing relationship with inorganic semiconductors such as silicon and gallium arsenide. Furthermore, advances in fields such as nano-medicine and bioelectronics, and the impending revolution of the ‘ubiquitous sensor network’, all require new functional materials which are bio-compatible, cheap, have minimal embedded manufacturing energy plus extremely low power consumption, and are mechanically robust and flexible for integration with tissues, building structures, fabrics and all manner of hosts. In this short review article we summarize current progress in creating materials with such properties. We focus primarily on organic and bio-organic electronic and optoelectronic systems derived from or inspired by nature, and outline the complex charge transport and photo-physics which control their behaviour. We also introduce the concept of electrical devices based upon ion or proton flow (‘ionics and protonics’) and focus particularly on their role as a signal interface with biological systems. Finally, we highlight recent advances in creating working devices, some of which have bio-inspired architectures, and summarize the current issues, challenges and potential solutions. This is a rich new playground for the modern materials physicist.

330 citations


Journal ArticleDOI
TL;DR: In this article, the authors place a dielectric elastomer near the verge of snap-through instability, trigger the instability with voltage, and bend the snapthrough path to avert electric breakdown.
Abstract: Dielectric elastomers are capable of large voltage-induced deformation, but achieving such large deformation in practice has been a major challenge due to electromechanical instability and electric breakdown. The complex nonlinear behavior suggests an important opportunity: electromechanical instability can be harnessed to achieve giant voltage-induced deformation. We introduce the following principle of operation: place a dielectric elastomer near the verge of snap-through instability, trigger the instability with voltage, and bend the snap-through path to avert electric breakdown. We demonstrate this principle of operation with a commonly used experimental setup—a dielectric membrane mounted on a chamber of air. The behavior of the membrane can be changed dramatically by varying parameters such as the initial pressure in the chamber, the volume of the chamber, and the prestretch of the membrane. We use a computational model to analyze inhomogeneous deformation and map out bifurcation diagrams to guide the experiment. With suitable values of the parameters, we obtain giant voltage-induced expansion of area by 1692%, far beyond the largest value reported in the literature.

302 citations


Journal ArticleDOI
TL;DR: A series of highly luminescent dinuclear copper(I) complexes has been synthesized in good yields using a modular ligand system of easily accessible diphenylphosphinopyridine-type P^N ligands, revealing a dinuclear complex structure with a butterfly-shaped metal-halide core.
Abstract: A series of highly luminescent dinuclear copper(I) complexes has been synthesized in good yields using a modular ligand system of easily accessible diphenylphosphinopyridine-type P^N ligands. Characterization of these complexes via X-ray crystallographic studies and elemental analysis revealed a dinuclear complex structure with a butterfly-shaped metal-halide core. The complexes feature emission covering the visible spectrum from blue to red together with high quantum yields up to 96%. Density functional theory calculations show that the HOMO consists mainly of orbitals of both the metal core and the bridging halides, while the LUMO resides dominantly on the heterocyclic part of the P^N ligands. Therefore, modification of the heterocyclic moiety of the bridging ligand allows for systematic tuning of the luminescence wavelength. By increasing the aromatic system of the N-heterocycle or through functionalization of the pyridyl moiety, complexes with emission maxima from 481 to 713 nm are obtained. For a rep...

300 citations


Journal ArticleDOI
TL;DR: This paper proposes LineUp - a novel and scalable visualization technique that uses bar charts that enables users to interactively combine attributes and flexibly refine parameters to explore the effect of changes in the attribute combination.
Abstract: Rankings are a popular and universal approach to structuring otherwise unorganized collections of items by computing a rank for each item based on the value of one or more of its attributes. This allows us, for example, to prioritize tasks or to evaluate the performance of products relative to each other. While the visualization of a ranking itself is straightforward, its interpretation is not, because the rank of an item represents only a summary of a potentially complicated relationship between its attributes and those of the other items. It is also common that alternative rankings exist which need to be compared and analyzed to gain insight into how multiple heterogeneous attributes affect the rankings. Advanced visual exploration tools are needed to make this process efficient. In this paper we present a comprehensive analysis of requirements for the visualization of multi-attribute rankings. Based on these considerations, we propose LineUp - a novel and scalable visualization technique that uses bar charts. This interactive technique supports the ranking of items based on multiple heterogeneous attributes with different scales and semantics. It enables users to interactively combine attributes and flexibly refine parameters to explore the effect of changes in the attribute combination. This process can be employed to derive actionable insights as to which attributes of an item need to be modified in order for its rank to change. Additionally, through integration of slope graphs, LineUp can also be used to compare multiple alternative rankings on the same set of items, for example, over time or across different attribute combinations. We evaluate the effectiveness of the proposed multi-attribute visualization technique in a qualitative study. The study shows that users are able to successfully solve complex ranking tasks in a short period of time.

296 citations


Journal ArticleDOI
TL;DR: By incorporation of aluminum or arsenic in the GaP nanowires, the emitted wavelength is tuned across an important range of the visible light spectrum (555–690 nm), which enables new pathways to tailor materials properties enhancing the functionality.
Abstract: The main challenge for light-emitting diodes is to increase the efficiency in the green part of the spectrum. Gallium phosphide (GaP) with the normal cubic crystal structure has an indirect band gap, which severely limits the green emission efficiency. Band structure calculations have predicted a direct band gap for wurtzite GaP. Here, we report the fabrication of GaP nanowires with pure hexagonal crystal structure and demonstrate the direct nature of the band gap. We observe strong photoluminescence at a wavelength of 594 nm with short lifetime, typical for a direct band gap. Furthermore, by incorporation of aluminum or arsenic in the GaP nanowires, the emitted wavelength is tuned across an important range of the visible light spectrum (555–690 nm). This approach of crystal structure engineering enables new pathways to tailor materials properties enhancing the functionality.

Proceedings ArticleDOI
29 Oct 2013
TL;DR: This work describes a new approach to virtual machine (VM) construction that amortizes much of the effort in initial construction by allowing new languages to be implemented with modest additional effort, and suggests that high performance is attainable while preserving a modular and layered architecture.
Abstract: Building high-performance virtual machines is a complex and expensive undertaking; many popular languages still have low-performance implementations. We describe a new approach to virtual machine (VM) construction that amortizes much of the effort in initial construction by allowing new languages to be implemented with modest additional effort. The approach relies on abstract syntax tree (AST) interpretation where a node can rewrite itself to a more specialized or more general node, together with an optimizing compiler that exploits the structure of the interpreter. The compiler uses speculative assumptions and deoptimization in order to produce efficient machine code. Our initial experience suggests that high performance is attainable while preserving a modular and layered architecture, and that new high-performance language implementations can be obtained by writing little more than a stylized interpreter.

Journal ArticleDOI
TL;DR: This article aims to highlight recent work on application of nature-inspired H-bonded organic molecules in organic electronic devices and exploitation of H- bonding for supramolecular assembly of organic conductors.
Abstract: Hydrogen-bonding (H-bonding) is a relatively strong, highly directional, and specific noncovalent interaction present in many organic molecules, and notably is responsible for supramolecular ordering in biological systems. The H-bonding interactions play a role in many organic electrically conducting materials – in particular in those related to biology, e.g. melanin and indigo. This article aims to highlight recent work on application of nature-inspired H-bonded organic molecules in organic electronic devices. Three topics are covered in this brief review: (1) electrical and ionic conduction in natural H-bonded systems, (2) semiconducting properties of H-bonded organic pigments, and (3) exploitation of H-bonding for supramolecular assembly of organic conductors. H-bonding interactions are ubiquitous in biology, thus making the study of H-bonded organic semiconductors highly pertinent where interfacing of electronics with biological systems is desired.

Journal ArticleDOI
TL;DR: Two inkjet pigments, epindolidione and quinacridone, that break this design rule are explored and afford intermolecular π-stacking reinforced by hydrogen-bonding bridges, and air-stable organic field effect transistors are reported.
Abstract: Extensive intramolecular π-conjugation is considered to be requisite in the design of organic semiconductors. Here, two inkjet pigments, epindolidione and quinacridone, that break this design rule are explored. These molecules afford intermolecular π-stacking reinforced by hydrogen-bonding bridges. Air-stable organic field effect transistors are reported that support mobilities up to 1.5 cm(2)/Vs with T80 lifetimes comparable with the most stable reported organic semiconducting materials.

Journal ArticleDOI
TL;DR: Two demonstrations of electronic skins, which combine temperature and pressure sensing with integrated thermal actuators and organic displays, unveil the potential of these devices for robotics and clinical applications.
Abstract: Advances in materials science and layout design have enabled the realization of flexible and multifunctional electronic devices. Two demonstrations of electronic skins, which combine temperature and pressure sensing with integrated thermal actuators and organic displays, unveil the potential of these devices for robotics and clinical applications.

Journal ArticleDOI
TL;DR: This progress report aims to logically bridge together the hereto independent research directions on indigo, isoindigo, and other materials inspired by historical dye chemistry: a field which was the root of the development of modern chemistry in the first place.
Abstract: Indigo and its derivatives are dyes and pigments with a long and distinguished history in organic chemistry. Recently, applications of this 'old' structure as a functional organic building block for organic electronics applications have renewed interest in these molecules and their remarkable chemical and physical properties. Natural-origin indigos have been processed in fully bio-compatible field effect transistors, operating with ambipolar mobilities up to 0.5 cm(2) /Vs and air-stability. The synthetic derivative isoindigo has emerged as one of the most successful building-blocks for semiconducting polymers for plastic solar cells with efficiencies > 5%. Another isomer of indigo, epindolidione, has also been shown to be one of the best reported organic transistor materials in terms of mobility (∼2 cm(2) /Vs) and stability. This progress report aims to review very recent applications of indigoids in organic electronics, but especially to logically bridge together the hereto independent research directions on indigo, isoindigo, and other materials inspired by historical dye chemistry: a field which was the root of the development of modern chemistry in the first place.

Journal ArticleDOI
TL;DR: It is concluded that SOCE is activated through dynamic interplay between STIM1 and Orai1 helices, and a trypsin-resistant CC1–CC2 fragment in the apo and ORAi1-bound states is presented.
Abstract: Orai1 calcium channels in the plasma membrane are activated by stromal interaction molecule-1 (STIM1), an endoplasmic reticulum calcium sensor, to mediate store-operated calcium entry (SOCE). The cytosolic region of STIM1 contains a long putative coiled-coil (CC)1 segment and shorter CC2 and CC3 domains. Here we present solution nuclear magnetic resonance structures of a trypsin-resistant CC1-CC2 fragment in the apo and Orai1-bound states. Each CC1-CC2 subunit forms a U-shaped structure that homodimerizes through antiparallel interactions between equivalent α-helices. The CC2:CC2' helix pair clamps two identical acidic Orai1 C-terminal helices at opposite ends of a hydrophobic/basic STIM-Orai association pocket. STIM1 mutants disrupting CC1:CC1' interactions attenuate, while variants promoting CC1 stability spontaneously activate Orai1 currents. CC2 mutations cause remarkable variability in Orai1 activation because of a dual function in binding Orai1 and autoinhibiting STIM1 oligomerization via interactions with CC3. We conclude that SOCE is activated through dynamic interplay between STIM1 and Orai1 helices.

Journal ArticleDOI
TL;DR: Using visible light for two-photon DLW and STED, lateral structure sizes are obtained of 55 nm, a Sparrow limit of around 100 nm and two clearly separated lines spaced only 120 nm apart are presented.
Abstract: Two–photon direct laser writing (DLW) lithography is limited in the achievable structure size as well as in structure resolution. Adding stimulated emission depletion (STED) to DLW allowed overcoming both restrictions. We now push both to new limits. Using visible light for two-photon DLW (780 nm) and STED (532 nm), we obtain lateral structure sizes of 55 nm, a Sparrow limit of around 100 nm and we present two clearly separated lines spaced only 120 nm apart. The photo-resist used in these experiments is a mixture of tri- and tetra-acrylates and 7-Diethylamino-3-thenoylcoumarin as a photo-starter which can be readily quenched via STED.

Journal ArticleDOI
TL;DR: In this article, the authors used interviews with inspection officials and a document analysis to reconstruct the "program theories" (i.e., the assumptions on causal mechanisms, linking school inspections to their intended outcomes of improved teaching and learning) of Inspectorates of Education in six European countries.
Abstract: School inspection is used by most European education systems as a major instrument for controlling and promoting the quality of schools. Surprisingly, there is little research knowledge about how school inspections drive the improvement of schools and which types of approaches are most effective and cause the least unintended consequences. The study presented in this paper uses interviews with inspection officials and a document analysis to reconstruct the “program theories” (i.e. the assumptions on causal mechanisms, linking school inspections to their intended outcomes of improved teaching and learning) of Inspectorates of Education in six European countries. The results section of the paper starts with a summary of the commonalities and differences of these six national inspection models with respect to standards and thresholds used, to types of feedback and reporting, and to the sanctions, rewards and interventions applied to motivate schools to improve. Next, the intermediate processes through which these inspection models are expected to promote good education (e.g. through actions of stakeholders) are explained. In the concluding section, these assumptions are critically discussed in the light of research knowledge.

Journal ArticleDOI
TL;DR: A bottom up approach for modeling photosynthetic light-harvesting and the Hamiltonian of pigment-protein complexes is discussed, using quantum mechanics perturbation theory to provide a microscopic foundation for the standard PPC Hamiltonian.
Abstract: We discuss a bottom up approach for modeling photosynthetic light-harvesting Methods are reviewed for a full structure-based parameterization of the Hamiltonian of pigment–protein complexes (PPCs) These parameters comprise (i) the local transition energies of the pigments in their binding sites in the protein, the site energies; (ii) the couplings between optical transitions of the pigments, the excitonic couplings; and (iii) the spectral density characterizing the dynamic modulation of pigment transition energies and excitonic couplings by protein vibrations Starting with quantum mechanics perturbation theory, we provide a microscopic foundation for the standard PPC Hamiltonian and relate the expressions obtained for its matrix elements to quantities that can be calculated with classical molecular mechanics/electrostatics approaches including the whole PPC in atomic detail and using charge and transition densities obtained with quantum chemical calculations on the isolated building blocks of the PPC In the second part of this perspective, the Hamiltonian is utilized to describe the quantum dynamics of excitons Situations are discussed that differ in the relative strength of excitonic and exciton-vibrational coupling The predictive power of the approaches is demonstrated in application to different PPCs, and challenges for future work are outlined

Journal ArticleDOI
TL;DR: An overview of methods for music similarity estimation and music recommendation based on music context data is given and the characteristics of the presented context-based measures are elaborates and discusses their strengths as well as their weaknesses.
Abstract: In this survey article, we give an overview of methods for music similarity estimation and music recommendation based on music context data. Unlike approaches that rely on music content and have been researched for almost two decades, music-context-based (or contextual) approaches to music retrieval are a quite recent field of research within music information retrieval (MIR). Contextual data refers to all music-relevant information that is not included in the audio signal itself. In this article, we focus on contextual aspects of music primarily accessible through web technology. We discuss different sources of context-based data for individual music pieces and for music artists. We summarize various approaches for constructing similarity measures based on the collaborative or cultural knowledge incorporated into these data sources. In particular, we identify and review three main types of context-based similarity approaches: text-retrieval-based approaches (relying on web-texts, tags, or lyrics), co-occurrence-based approaches (relying on playlists, page counts, microblogs, or peer-to-peer-networks), and approaches based on user ratings or listening habits. This article elaborates the characteristics of the presented context-based measures and discusses their strengths as well as their weaknesses.

Journal ArticleDOI
TL;DR: In this article, a large-scale experimental study showed that a forced-choice full binary format (where respondents have to tick “yes” and “no” for each destination-attribute combination) performs better than both current preferred formats in academic and applied studies.
Abstract: Destination image is among the most frequently measured constructs in empirical survey research. Academic tourism researchers tend to use multi-category scales, often referring to them as “Likert scales,” while industry typically uses “pick-any” measures. But which leads to results that are more valid? Findings from a large-scale experimental study show that a “forced-choice full binary” format (where respondents have to tick “yes” and “no” for each destination-attribute combination) performs better than both current preferred formats in academic and applied studies.

Book ChapterDOI
TL;DR: This survey article presents difference field algorithms for symbolic summation that can be solved completely automatically for large scale summation problems for the evaluation of Feynman diagrams in QCD (Quantum ChromoDynamics).
Abstract: In this survey article we present difference field algorithms for symbolic summation. Special emphasize is put on new aspects in how the summation problems are rephrased in terms of difference fields, how the problems are solved there, and how the derived results in the given difference field can be reinterpreted as solutions of the input problem. The algorithms are illustrated with the Mathematica package Sigma by discovering and proving new harmonic number identities extending those from Paule and Schneider, 2003. In addition, the newly developed package EvaluateMultiSums is introduced that combines the presented tools. In this way, large scale summation problems for the evaluation of Feynman diagrams in QCD (Quantum ChromoDynamics) can be solved completely automatically.

Proceedings ArticleDOI
22 Apr 2013
TL;DR: This chapter considers security terminology, security bugs, security flaws, and mitigation issues in the context of software security.
Abstract: The importance of IT security is out of doubt. Data, computer and network security are essential for any business or organization. Software security often remains out of focus, from an organization's, a developer's and from an end-user's point of view. We will consider security terminology, security bugs, security flaws, and mitigation issues.

Proceedings ArticleDOI
17 Jun 2013
TL;DR: A Linear Model Predictive Control approach to Cooperative Adaptive Cruise Control is presented, directly minimizing the fuel consumption rather than the acceleration of the vehicle, using the nonlinear static fuel consumption map of the internal combustion engine.
Abstract: Reduction of fuel consumption is one of the primary goals of modern automotive engineering. While in the past the focus was on more efficient engine design and control there is an upcoming interest on economic context aware control of the complete vehicle. Technical progress will enable future vehicles to interact with other traffic participants and the surrounding infrastructure, collecting information which allow for reduction of fuel consumption by predictive vehicle control strategies. The principle of Model Predictive Control allows a straightforward integration of e.g. navigation systems, on-board radar sensors, V2V- and V2I-communication whilst regarding constraints and dynamic of the system. This paper presents a Linear Model Predictive Control approach to Cooperative Adaptive Cruise Control, directly minimizing the fuel consumption rather than the acceleration of the vehicle. To this end the nonlinear static fuel consumption map of the internal combustion engine is included into the control design by a piecewise quadratic approximation. Inclusion of a linear spacing policy prevents rear end collisions. Simulation results demonstrate the fuel and road capacity benefits, for a single vehicle and for a string of vehicles, equipped with the proposed control, in comparison to vehicles operated by a non-cooperative adaptive cruise control. Full information on the speed prediction of the predecessor is assumed, hence the purpose of this paper is twofold. On the one hand, best achievable benefits, of the proposed control, due to perfect prediction are demonstrated. On the other hand, the paper studies the behavior of the considered control and the influence of the prediction horizon.

Journal ArticleDOI
TL;DR: In this article, a review of the current state of the art of compatibilization methods for natural fiber composites and wood polymer composites is presented, and a ranking of the methods based on their effects on material properties such as tensile/flexural strength and modulus, impact strength and water absorption is presented.
Abstract: Numerous strategies to improve the fiber–matrix interaction in natural fiber composites (NFCs) and wood polymer composites (WPCs) have been proposed and investigated. We have reviewed literature on polyolefin-based NFCs and WPCs to get an overview of the current state of the art of compatibilization methods. Those are classified in two categories here, namely fiber-based strategies and matrix-based strategies. Although this issue has been covered by several reviews before, as yet no work exists that is focused on polyolefin-based NFCs and WPCs. Furthermore, a ranking of the compatibilization methods based on their effects on material properties such as tensile/flexural strength and modulus, impact strength and water absorption, allows for an assessment of the efficiency of the various methods. As to the fiber-based strategies, silanes, maleated polyolefins (MA-POs), mercerization and acetylation are most thoroughly investigated. Silanes are most effective judged by achievable material property improvements, allowing for increases in tensile and flexural strength of more than 100%. Among the matrix-based strategies, MA-POs and isocyanates are most prominent in the literature. The first class enables the more significant material improvements, with reported increases of tensile and flexural strength of 132% and 85%, respectively. While strengths can be enhanced by many compatibilization methods, moduli, and impact strength (notched in particular) are in most cases improved to a lesser degree or even reduced. Especially, the last point calls for further attention, because impact strength is still a weak point of NFCs and WPCs. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2013

Journal ArticleDOI
TL;DR: In this paper, the electrical breakdown field strength of a dielectric elastomer has been investigated for the measurement of the stretch dependence of electrical breakdown strength of the elastomers.
Abstract: Dielectric elastomers are used for electromechanical energy conversion in actuators and in harvesting mechanical energy from renewable sources. The electrical breakdown strength determines the limit of a dielectric elastomer for its use in actuators and energy harvesters. We report two experimental configurations for the measurement of the stretch dependence of the electrical breakdown strength of dielectric elastomers, and compare the electrical breakdown fields for compliant and rigid electrodes on the elastomer. We show that the electrode configuration strongly influences the electrical breakdown field strength. Further, we compare the stretch dependent dielectric function and breakdown of the acrylic elastomer VHB 4910 TM from 3M TM , and of the natural rubber ZruElast TM A1040 TM from Zrunek rubber technology. While the dielectric permittivity of VHB decreases with increasing stretch ratio, the dielectric constant of rubber is insensitive to stretch. Our results suggest natural rubber as a versatile material for dielectric elastomer energy harvesting. (Some figures may appear in colour only in the online journal)

Journal ArticleDOI
TL;DR: This paper examines the state-of-the-art and provides further investigations and concepts regarding the following interpretability aspects: distinguishability, simplicity, consistency, coverage and completeness, feature importance levels, rule importance levels and interpretation of consequents.

Journal ArticleDOI
TL;DR: In this paper, a model for assessing economic losses caused by electricity cuts as well as willingness-to-pay to avoid these power outages as an approximation to the value of supply security is presented.

Journal ArticleDOI
01 Dec 2013
TL;DR: This article investigates and discusses literature on the topic of user-centric music retrieval and reflects on why the breakthrough in this field has not been achieved yet, and presents ideas on aspects crucial to consider when elaborating user-aware music retrieval systems.
Abstract: Personalization and context-awareness are highly important topics in research on Intelligent Information Systems. In the fields of Music Information Retrieval (MIR) and Music Recommendation in particular, user-centric algorithms should ideally provide music that perfectly fits each individual listener in each imaginable situation and for each of her information or entertainment needs. Even though preliminary steps towards such systems have recently been presented at the "International Society for Music Information Retrieval Conference" (ISMIR) and at similar venues, this vision is still far away from becoming a reality. In this article, we investigate and discuss literature on the topic of user-centric music retrieval and reflect on why the breakthrough in this field has not been achieved yet. Given the different expertises of the authors, we shed light on why this topic is a particularly challenging one, taking computer science and psychology points of view. Whereas the computer science aspect centers on the problems of user modeling, machine learning, and evaluation, the psychological discussion is mainly concerned with proper experimental design and interpretation of the results of an experiment. We further present our ideas on aspects crucial to consider when elaborating user-aware music retrieval systems.