Showing papers by "Johannes Kepler University of Linz published in 2012"

Ultrathin and lightweight organic solar cells with high flexibility

Abstract: Organic solar cells are promising for technological applications, as they are lightweight and mechanically robust. This study presents flexible organic solar cells that are less than 2 μm thick, have very low specific weight and maintain their photovoltaic performance under repeated mechanical deformation.

Business Cases for Sustainability: The Role of Business Model Innovation for Corporate Sustainability

Abstract: A considerable body of literature deals with the creation of economic value while increasing corporate environmental and social performance. Some publications even focus on the business case for sustainability which aims at increasing corporate economic value through environmental or social measures. The existence of a business case for sustainability is, however, mostly seen as an ad hoc measure, a supplement to the core business, or simply a coincidence. As a contrast, this paper argues that business model innovations may be required to support a systematic, ongoing creation of business cases for sustainability. A framework for business model innovation is proposed as a means to strategically create business cases on a regular basis as an inherent, deeply integrated element of business activities.

The Dynamic Capability View in Strategic Management: A Bibliometric Review

Abstract: The dynamic capability view (DCV) is one of the most vibrant approaches to strategic management. In this study, the extant literature published between 1994 and 2011 is analysed, using bibliometric methods in order to explore the scope of this approach and detect current research priorities. For this purpose, the method of bibliographic coupling is introduced in management research, which shifts the focus of analysis from past traditions to current trends. Several clusters of thematically related research are extracted from bibliographic networks, which represent interconnected yet distinct subfields of inquiry within the DCV. The core cluster of the current DCV, which visualizes this research field's nascent but fragile identity, focuses on learning and change capabilities and relates them to firm performance, thus merging aspects of organization theory and strategic management. In addition, several peripheral clusters of research are identified, which reflect a parallel process of differentiation in the overall field. Both trends, i.e. of integration and differentiation, attest to the emancipation of the DCV as a distinct approach to strategic management. However, the DCV still lacks consensual concepts that allow comparisons of empirical studies and advance the theoretical understanding of dynamic capabilities. In the light of the above, some implications of this analysis for further research are discussed.

Materials for stretchable electronics

Abstract: Electronics can be made on elastically stretchable “skin.” Such skins conform to irregularly curved surfaces and carry arrays of thin-film devices and integrated circuits. Laypeople and scientists intuitively grasp the concept of electronic skins; material scientists then ask “what materials are used?” and “how does it work?” Stretchable circuits are made of diverse materials that span more than 12 orders of magnitude in elastic modulus. We begin with a brief overview of the materials and the architecture of stretchable electronics, then we discuss stretchable substrates, encapsulation, interconnects, and the fabrication of devices and circuits. These components and techniques provide the tools for creating new concepts in biocompatible circuits that conform to and stretch with living tissue. They enable wireless energy transfer via stretchable antennas, stretchable solar cells that convert sunlight to electricity, supercapacitors, and batteries that store energy in stretchable electronic devices. We conclude with a brief outlook on the technical challenges for this revolutionary technology on its road to functional stretchable electronic systems.

cn.MOPS: mixture of Poissons for discovering copy number variations in next-generation sequencing data with a low false discovery rate

Abstract: Quantitative analyses of next-generation sequencing (NGS) data, such as the detection of copy number variations (CNVs), remain challenging. Current methods detect CNVs as changes in the depth of coverage along chromosomes. Technological or genomic variations in the depth of coverage thus lead to a high false discovery rate (FDR), even upon correction for GC content. In the context of association studies between CNVs and disease, a high FDR means many false CNVs, thereby decreasing the discovery power of the study after correction for multiple testing. We propose ‘Copy Number estimation by a Mixture Of PoissonS’ (cn.MOPS), a data processing pipeline for CNV detection in NGS data. In contrast to previous approaches, cn.MOPS incorporates modeling of depths of coverage across samples at each genomic position. Therefore, cn.MOPS is not affected by read count variations along chromosomes. Using a Bayesian approach, cn.MOPS decomposes variations in the depth of coverage across samples into integer copy numbers and noise by means of its mixture components and Poisson distributions, respectively. The noise estimate allows for reducing the FDR by filtering out detections having high noise that are likely to be false detections. We compared cn.MOPS with the five most popular methods for CNV detection in NGS data using four benchmark datasets: (i) simulated data, (ii) NGS data from a male HapMap individual with implanted CNVs from the X chromosome, (iii) data from HapMap individuals with known CNVs, (iv) high coverage data from the 1000 Genomes Project. cn.MOPS outperformed its five competitors in terms of precision (1–FDR) and recall for both gains and losses in all benchmark data sets. The software cn.MOPS is publicly available as an R package at http://www.bioinf.jku.at/ software/cnmops/ and at Bioconductor.

Indigo - a natural pigment for high performance ambipolar organic field effect transistors and circuits

Abstract: strong intermolecular interactions and with reversible reduction and oxidation reactions characterized by means of optical, electrical, and morphological investigations on thin indigo fi lms. The OFETs and complementary-like inverters are among the best reported organic devices to date, in terms of mobility, voltage gain, symmetry, p- and n-type channel balance, low operating voltage window and high ON/OFF ratio. Moreover, these devices show that high performance electronics can be fabricated entirely from non-toxic, biodegradable, and extremely cheap materials.

Harnessing snap-through instability in soft dielectrics to achieve giant voltage-triggered deformation

Abstract: A soft dielectric membrane is prone to snap-through instability. We present theory and experiment to show that the instability can be harnessed to achieve giant voltage-triggered deformation. We mount a membrane on a chamber of a suitable volume, pressurize the membrane into a state near the verge of the instability, and apply a voltage to trigger the snap without causing electrical breakdown. For an acrylic membrane we demonstrate voltage-triggered expansion of area by 1692%, far beyond the largest value reported in the literature. The large expansion can even be retained after the voltage is switched off.

Design of computer experiments: space filling and beyond

Abstract: When setting up a computer experiment, it has become a standard practice to select the inputs spread out uniformly across the available space. These so-called space-filling designs are now ubiquitous in corresponding publications and conferences. The statistical folklore is that such designs have superior properties when it comes to prediction and estimation of emulator functions. In this paper we want to review the circumstances under which this superiority holds, provide some new arguments and clarify the motives to go beyond space-filling. An overview over the state of the art of space-filling is introducing and complementing these results.

Shadow economies around the world: novel insights, accepted knowledge, and new estimates

Abstract: This paper is a first attempt to study the impact of enforcement on the shadow economy. Using a MIMIC model, we find that a higher share of sub-national government employment and the aspiration of public employees to follow rules significantly deter shadow economic activities. Our results also confirm previous findings: Increased burdens of taxation and regulation as well as the state of the “official” economy are important determinants of the shadow economy. The estimated weighted average informality in 162 countries around the world, including developing, Eastern European, Central Asian, and high-income OECD countries, is 17.1% of “official” GDP.

Cool features and tough decisions: a comparison of variability modeling approaches

Abstract: Variability modeling is essential for defining and managing the commonalities and variabilities in software product lines. Numerous variability modeling approaches exist today to support domain and application engineering activities. Most are based on feature modeling (FM) or decision modeling (DM), but so far no systematic comparison exists between these two classes of approaches. Over the last two decades many new features have been added to both FM and DM and it is tough to decide which approach to use for what purpose. This paper clarifies the relation between FM and DM. We aim to systematize the research field of variability modeling and to explore potential synergies. We compare multiple aspects of FM and DM ranging from historical origins and rationale, through syntactic and semantic richness, to tool support, identifying commonalities and differences. We hope that this effort will improve the understanding of the range of approaches to variability modeling by discussing the possible variations. This will provide insights to users considering adopting variability modeling in practice and to designers of new languages, such as the new OMG Common Variability Language.

Marine sulfate-reducing bacteria cause serious corrosion of iron under electroconductive biogenic mineral crust

Abstract: Iron (Fe0) corrosion in anoxic environments (e.g. inside pipelines), a process entailing considerable economic costs, is largely influenced by microorganisms, in particular sulfate-reducing bacteria (SRB). The process is characterized by formation of black crusts and metal pitting. The mechanism is usually explained by the corrosiveness of formed H2S, and scavenge of ‘cathodic’ H2 from chemical reaction of Fe0 with H2O. Here we studied peculiar marine SRB that grew lithotrophically with metallic iron as the only electron donor. They degraded up to 72% of iron coupons (10 mm × 10 mm × 1 mm) within five months, which is a technologically highly relevant corrosion rate (0.7 mm Fe0 year−1), while conventional H2-scavenging control strains were not corrosive. The black, hard mineral crust (FeS, FeCO3, Mg/CaCO3) deposited on the corroding metal exhibited electrical conductivity (50 S m−1). This was sufficient to explain the corrosion rate by electron flow from the metal (4Fe0 → 4Fe2+ + 8e−) through semiconductive sulfides to the crust-colonizing cells reducing sulfate (8e− + SO42− + 9H+ → HS− + 4H2O). Hence, anaerobic microbial iron corrosion obviously bypasses H2 rather than depends on it. SRB with such corrosive potential were revealed at naturally high numbers at a coastal marine sediment site. Iron coupons buried there were corroded and covered by the characteristic mineral crust. It is speculated that anaerobic biocorrosion is due to the promiscuous use of an ecophysiologically relevant catabolic trait for uptake of external electrons from abiotic or biotic sources in sediments.

Imaging of plant cell walls by confocal Raman microscopy

Abstract: Raman imaging of plant cell walls represents a nondestructive technique that can provide insights into chemical composition in context with structure at the micrometer level (<0.5 μm). The major steps of the experimental procedure are described: sample preparation (embedding and microcutting), setting the mapping parameters, and finally the calculation of chemical images on the basis of the acquired Raman spectra. Every Raman image is based on thousands of spectra, each being a spatially resolved molecular 'fingerprint' of the cell wall. Multiple components are analyzed within the native cell walls, and insights into polymer composition as well as the orientation of the cellulose microfibrils can be gained. The most labor-intensive step of this process is often the sample preparation, as the imaging approach requires a flat surface of the plant tissue with intact cell walls. After finishing the map (acquisition time is ∼10 min to 10 h, depending on the size of the region of interest and scanning parameters), many possibilities exist for the analysis of spectral data and image generation.

Sensing the "Health State" of a Community

Abstract: Mobile phones are a pervasive platform for opportunistic sensing of behaviors and opinions. Three studies use location and communication sensors to model individual behaviors and symptoms, long-term health outcomes, and the diffusion of opinions in a community. These three analyses illustrate how mobile phones can unobtrusively monitor rich social interactions, because the underlying sensing technologies are now commonplace and readily available.

Subject-Oriented Business Process Management

Abstract: Activities performed in organizations are coordinated via communication between the people involved The sentences used to communicate are naturally structured by subject, verb, and object The subject describes the actor, the verb the action and the object what is affected by the action Subject-oriented Business Process Management (S-BPM) as presented in this book is based on this simple structure which enables process-oriented thinking and process modeling S-BPM puts the subject of a process at the center of attention and thus deals with business processes and their organizational environment from a new perspective, meeting organizational requirements in a much better way than traditional approaches Subjects represent agents of an action in a process, which can be either technical or human (eg a thread in an IT system or a clerk) A process structures the actions of each subject and coordinates the required communication among the subjects S-BPM provides a coherent procedural framework to model and analyze business processes: its focus is the cooperation of all stakeholders involved in the strategic, tactical, and operational issues, sharing their knowledge in a networked structure The authors illustrate how each modeling activity through the whole development lifecycle can be supported through the use of appropriate software tools The presentation style focuses on professionals in industry, and on students specializing in process management or organizational modeling Each chapter begins with a summary of key findings and is full of examples, hints, and possible pitfalls An interpreter model, a toolbox, and a glossary summarizing the main terms complete the book The web site wwwi2pmnet provides additional software tools and further material

Intermolecular hybridization governs molecular electrical doping.

Abstract: Current models for molecular electrical doping of organic semiconductors are found to be at odds with other well-established concepts in that field, like polaron formation. Addressing these inconsistencies for prototypical systems, we present experimental and theoretical evidence for intermolecular hybridization of organic semiconductor and dopant frontier molecular orbitals. Common doping-related observations are attributed to this phenomenon, and controlling the degree of hybridization emerges as a strategy for overcoming the present limitations in the yield of doping-induced charge carriers.

Datacenter at the Airport: Reasoning about Time-Dependent Parking Lot Occupancy

Abstract: Recently, Olariu et al. [3], [7], [18], [19], [20] proposed to refer to a dynamic group of vehicles whose excess computing, sensing, communication, and storage resources can be coordinated and dynamically allocated to authorized users, as a vehicular cloud. One of the characteristics that distinguishes vehicular clouds from conventional clouds is the dynamically changing amount of available resources that, in some cases, may fluctuate rather abruptly. In this work, we envision a vehicular cloud involving cars in the long-term parking lot of a typical international airport. The patrons of such a parking lot are typically on travel for several days, providing a pool of cars that can serve as the basis for a datacenter at the airport. We anticipate a park and plug scenario where the cars that participate in the vehicular cloud are plugged into a standard power outlet and are provided Ethernet connection to a central server at the airport. In order to be able to schedule resources and to assign computational tasks to the various cars in the vehicular cloud, a fundamental prerequisite is to have an accurate picture of the number of vehicles that are expected to be present in the parking lot as a function of time. What makes the problem difficult is the time-varying nature of the arrival and departure rates. In this work, we concern ourselves with predicting the parking occupancy given time-varying arrival and departure rates. Our main contribution is to provide closed forms for the probability distribution of the parking lot occupancy as a function of time, for the expected number of cars in the parking lot and its variance, and for the limiting behavior of these parameters as time increases. In addition to analytical results, we have obtained a series of empirical results that confirm the accuracy of our analytical predictions.

Universal recovery of the energy-level degeneracy of bright excitons in InGaAs quantum dots without a structure symmetry.

Abstract: The lack of structural symmetry which usually characterizes semiconductor quantum dots lifts the energetic degeneracy of the bright excitonic states and hampers severely their use as high-fidelity sources of entangled photons. We demonstrate experimentally and theoretically that it is always possible to restore the excitonic degeneracy by the simultaneous application of large strain and electric fields. This is achieved by using one external perturbation to align the polarization of the exciton emission along the axis of the second perturbation, which then erases completely the energy splitting of the states. This result, which holds for any quantum dot structure, highlights the potential of combining complementary external fields to create artificial atoms meeting the stringent requirements posed by scalable semiconductor-based quantum technology.

Adaptive large neighborhood search for service technician routing and scheduling problems

Abstract: Motivated by the problem situation faced by infrastructure service and maintenance providers, we define the service technician routing and scheduling problem with and without team building: a given number of technicians have to complete a given number of service tasks. Each technician disposes of a number of skills at different levels and each task demands technicians that provide the appropriate skills of at least the demanded levels. Time windows at the different service sites have to be respected. In the case where a given task cannot be serviced by any of the technicians, outsourcing costs occur. In addition, in some companies technicians have to be grouped into teams at the beginning of the day since most of the tasks cannot be completed by a single technician. The objective is to minimize the sum of the total routing and outsourcing costs. We solve both problem versions by means of an adaptive large neighborhood search algorithm. It is tested on both artificial and real-world instances; high quality solutions are obtained within short computation times.

Inprocessing rules

Abstract: Decision procedures for Boolean satisfiability (SAT), especially modern conflict-driven clause learning (CDCL) solvers, act routinely as core solving engines in various real-world applications. Preprocessing, i.e., applying formula rewriting/simplification rules to the input formula before the actual search for satisfiability, has become an essential part of the SAT solving tool chain. Further, some of the strongest SAT solvers today add more reasoning to search by interleaving formula simplification and CDCL search. Such inprocessing SAT solvers witness the fact that implementing additional deduction rules in CDCL solvers leverages the efficiency of state-of-the-art SAT solving further. In this paper we establish formal underpinnings of inprocessing SAT solving via an abstract inprocessing framework that covers a wide range of modern SAT solving techniques.

The shadow economy and work in the shadow: What do we (not) know?

Abstract: In this paper the main focus lies on the shadow economy and on work in the shadow in OECD, developing and transition countries. Besides informal employment in the rural and non-rural sector also other measures of informal employment like the share of employees not covered by social security, own account workers or unpaid family workers are shown. The most influential factors on the shadow economy and/or shadow labor force are tax policies and state regulation, which, if they rise, increase both. Furthermore the discussion of the recent micro studies underline that economic opportunities, the overall burden of the state (taxes and regulations), the general situation on the labor market, and unemployment are crucial for an understanding of the dynamics of the shadow economy and especially the shadow labor force.

Analyzing Internet Forums

Abstract: Within Internet forums, members of certain (online) communities discuss matters of concern to the respective groups, with comparatively few social restraints. For radical, extremist, and other ideologically “sensitive” groups and organizations in particular, Internet forums are a very efficient and widely used tool to connect members, inform others about the group’s agenda, and attract new members. Whereas members of such groups may be reluctant to express their opinions in interviews or surveys, we argue that Internet forums can yield an abundance of useful “natural” discursive data for social scientific research. Based on two exemplary studies, we present a practical guide for the analysis of such data, including data-sampling strategies, the refinement of the data for computer-assisted qualitative and quantitative analysis, and strategies for in-depth analysis. The first study is an in-depth analysis of discourses within a German neo-Nazi discussion board. In the second, nine online forums for young Ge...

Polyphonic piano note transcription with recurrent neural networks

Abstract: In this paper a new approach for polyphonic piano note onset transcription is presented. It is based on a recurrent neural network to simultaneously detect the onsets and the pitches of the notes from spectral features. Long Short-Term Memory units are used in a bidirectional neural network to model the context of the notes. The use of a single regression output layer instead of the often used one-versus-all classification approach enables the system to significantly lower the number of erroneous note detections. Evaluation is based on common test sets and shows exceptional temporal precision combined with a significant boost in note transcription performance compared to current state-of-the-art approaches. The system is trained jointly with various synthesized piano instruments and real piano recordings and thus generalizes much better than existing systems.

Self-optimizing AST interpreters

Abstract: An abstract syntax tree (AST) interpreter is a simple and natural way to implement a programming language. However, it is also considered the slowest approach because of the high overhead of virtual method dispatch. Language implementers therefore define bytecodes to speed up interpretation, at the cost of introducing inflexible and hard to maintain bytecode formats. We present a novel approach to implementing AST interpreters in which the AST is modified during interpretation to incorporate type feedback. This tree rewriting is a general and powerful mechanism to optimize many constructs common in dynamic programming languages. Our system is implemented in Java and uses the static typing and primitive data types of Java elegantly to avoid the cost of boxed representations of primitive values in dynamic programming languages.

Indigo and Tyrian Purple – From Ancient Natural Dyes to Modern Organic Semiconductors

Abstract: We describe the history of indigo dye and its deriv- ative Tyrian purple, from their roles in the ancient world to recent research showing the semiconducting properties of indigoids. Indigoids are natural dyes that have been pro- duced for centuries, and indigo is currently the most pro- duced dye worldwide. Herein we review the history of these materials, their chemistry and physical properties, and their semiconducting characteristics in the solid state. Due to hy- drogen bonding and p-stacking, indigo and Tyrian purple form highly-ordered crystalline thin films. Such films have been used to fabricate high-performance organic field-effect transistors with ambipolar charge transport, as well as com- plementary-like circuits. Mobility values were found to be in the range of 10 � 2 -0.4 cm 2 /Vs. With performance on par with the best available organic semiconductors, indigoids dem- onstrate the potential of sustainable electronics based on biodegradable and biocompatible materials.