Showing papers by "Johannes Kepler University of Linz published in 2005"
TL;DR: In this paper, the authors present estimates of the shadow economy for 110 countries, including developing, transition and developed OECD economies, and the average size of shadow economy as a proportion of official GDP in 1999-2000 in developing countries was 41%, in transition countries 38, and in OECD countries 17%.
951 citations
Book•
01 Jan 2005TL;DR: This book discusses spatial augmented reality approaches that exploit optical elements, video projectors, holograms, radio frequency tags, and tracking technology, as well as interactive rendering algorithms and calibration techniques in order to embed synthetic supplements into the real environment or into a live video of thereal environment.
Abstract: Like virtual reality, augmented reality is becoming an emerging platform in new application areas for museums, edutainment, home entertainment, research, industry, and the art communities using novel approaches which have taken augmented reality beyond traditional eye-worn or hand-held displays. In this book, the authors discuss spatial augmented reality approaches that exploit optical elements, video projectors, holograms, radio frequency tags, and tracking technology, as well as interactive rendering algorithms and calibration techniques in order to embed synthetic supplements into the real environment or into a live video of the real environment. Special Features: - Comprehensive overview - Detailed mathematical equations - Code fragments - Implementation instructions - Examples of Spatial AR displays The authors have put together a preliminary collection of Errata. Updates will be posted to this site as necessary.
717 citations
19 Jun 2005
TL;DR: This work combines variable elimination with subsumption and self-subsuming resolution, and shows that these techniques not only shrink the formula further than previous preprocessing efforts based on variable elimination, but also decrease runtime of SAT solvers substantially for typical industrial SAT problems.
Abstract: Preprocessing SAT instances can reduce their size considerably. We combine variable elimination with subsumption and self-subsuming resolution, and show that these techniques not only shrink the formula further than previous preprocessing efforts based on variable elimination, but also decrease runtime of SAT solvers substantially for typical industrial SAT problems. We discuss critical implementation details that make the reduction procedure fast enough to be practical.
650 citations
01 Oct 2005
TL;DR: Two novel encodings of Boolean cardinality constraints in conjunctive normal form are given, one which requires only 7n clauses and 2n auxiliary variables, and another one demanding O(n·k) clauses, but with the advantage that inconsistencies can be detected in linear time by unit propagation alone.
Abstract: We consider the problem of encoding Boolean cardinality constraints in conjunctive normal form (CNF). Boolean cardinality constraints are formulae expressing that at most (resp. at least) k out of n propositional variables are true. We give two novel encodings that improve upon existing results, one which requires only 7n clauses and 2n auxiliary variables, and another one demanding O(n·k) clauses, but with the advantage that inconsistencies can be detected in linear time by unit propagation alone. Moreover, we prove a linear lower bound on the number of required clauses for any such encoding.
483 citations
TL;DR: A nonlocal variant of the well-known bounded variation regularization, which does not suffer from the staircase effect is defined and existence of a minimizer of the corresponding regularization functional for the denoising and deblurring problem is shown.
Abstract: This paper investigates the use of regularization functionals with nonlocal correlation terms for the problem of image denoising and image deblurring. These functionals are expressed as integrals o...
397 citations
29 Mar 2005
TL;DR: In this paper, the authors present a review of the history of organic photovoltaic materials and devices, and discuss the current state of the art in the field of solar cells.
Abstract: Foreword 1 Alan J. Heeger, Nobel Laureate, University of California at Santa Barbara Foreword 2 Aloysius F. Hepp and Sheila G. Bailey, Photovoltaic and Space Environments Branch, NASA Glenn Research Center Preface Acknowledgements Editors Contributors General Overviews The Story of Solar Cells J. Perlin Inorganic Photovoltaic Materials and Devices: Past, Present, and Future A.F. Hepp, S.G. Bailey, and R.P. Raffaelle Natural Organic Photosynthetic Solar Energy Transduction R.E. Blankenship Solid-State Organic Photovoltaics: A Review of Molecular and Polymeric Devices P.A. Lane and Z.H. Kafafi Mechanisms and Modeling Simulations of Optical Processes in Organic Photovoltaic Devices N-K. Persson and O. Inganas Coulomb Forces in Excitonic Solar Cells B.A. Gregg Electronic Structure of Organic Photovoltaic Materials: Modeling of Exciton-Dissociation and Charge-Recombination Processes J. Cornil, V. Lemaur, M.C. Steel, H. Dupin, A. Burquel, D. Beljonne, and J-L. Bredas Optimization of Organic Solar Cells in Both Space and Energy-Time Domains S-S. Sun and C.E. Bonner Materials and Devices Bulk Heterojunction Solar Cells H. Hoppe and N.S. Sariciftci Organic Solar Cells Incorporating a p-i-n Junction and a p-n Homojunction M. Hiramoto Liquid-Crystal Approaches to Organic Photovoltaics B. Kippelen, S. Yoo, J.A. Haddock, B. Domercq, S. Barlow, B. Minch, W. Xia, S.R. Marder, and N.R. Armstrong Photovoltaic Cells Based on Nanoporous Titania Films Filled with Conjugated Polymers K.M. Coakley and M.D. McGehee Solar Cells Based on Cyanine and Polymethine Dyes H. Tian and F. Meng Semiconductor Quantum Dot Based Nanocomposite Solar Cells M.H. Wu, A. Ueda, and R. Mu Solar Cells Based on Composites of Donor Conjugated Polymers and Carbon Nanotubes E. Kymakis and G.A.J. Amaratunga Photovoltaic Devices Based on Polythiophene/C60 L.S. Roman Alternating Fluorene Copolymer-Fullerene Blend Solar Cells O. Inganas, F. Zhang, X. Wang, A. Gadisa, N-K. Persson, M. Svensson, E. Perzon, W. Mammo, and M.R. Andersson Solar Cells Based on Diblock Copolymers: A PPV Donor Block and a Fullerene Derivatized Acceptor Block R.A. Segalman, C. Brochon, and G. Hadziioannou Interface Electronic Structure and Organic Photovoltaic Devices Y. Gao The Influence of the Electrode Choice on the Performance of Organic Solar Cells A.B. Djurisic' and C.Y. Kwong Conducting and Transparent Polymer Electrodes F. Zhang and O. Inganas Progress in Optically Transparent Conducting Polymers V. Seshadri and G.A. Sotzing Optoelectronic Properties of Conjugated Polymer/Fullerene Binary Pairs with Variety of LUMO Level Differences S. Sensfuss and M. Al-Ibrahim Polymer-Fullerene Concentration Gradient Photovoltaic Devices by Thermally Controlled Interdiffusion M. Drees, R.M. Davis, and R. Heflin Vertically Aligned Carbon Nanotubes for Organic Photovoltaic Devices M.H-C. Jin and L. Dai Index
324 citations
TL;DR: The temperature range of InAs nanowire growth is limited by the melting of the Au-In alloy, and the growth is instead assisted by a solid particle and does not occur at all when the particle is a liquid.
Abstract: We report the temperature dependence of the Au-assisted growth of InAs nanowires in MOVPE. Extensive studies of the growth of such nanowires have attributed growth to the so-called vapor-liquid-solid (VLS) mechanism, with a liquid Au-In alloy particle. We assert here that growth is instead assisted by a solid particle and does not occur at all when the particle is a liquid. Thus the temperature range of InAs nanowire growth is limited by the melting of the Au-In alloy. Comparison with growth of InAs nanowires in the same system assisted by a layer of SiO(x) is used to support this conclusion.
311 citations
TL;DR: It is found that bimolecular recombination in these efficient photovoltaic materials is orders of magnitude slower as compared to Langevin recombination expected for low-mobility materials.
Abstract: Bimolecular charge carrier recombination has been clarified in bulk-heterojunction solar cells based on a blend of regioregular poly(3-hexylthiophene) and 1-(3-methoxycarbonyl)propyl-1-phenyl-[6,6]-methanofullerene using the time-of-flight method. We show how bimolecular recombination influences the charge carrier transport, how it limits the efficiency of low-mobility solar cells, and how to estimate the bimolecular recombination coefficient. We found that bimolecular recombination in these efficient photovoltaic materials is orders of magnitude slower as compared to Langevin recombination expected for low-mobility materials. This effect is inherent to the nanomorphology of the bicontinuous interpenetrating network creating separate pathways for electrons and holes, and paves the way for the fabrication of bulk-heterojunction solar cells where bimolecular recombination is not the limiting factor.
308 citations
TL;DR: A survey of the latest developments in SAT-based formal verification, including incomplete methods such as bounded model checking and complete methods for model checking, focuses on how the surveyed techniques formulate the verification problem as a SAT problem and how they exploit crucial aspects of a SAT solver.
Abstract: Dramatic improvements in SAT solver technology over the last decade and the growing need for more efficient and scalable verification solutions have fueled research in verification methods based on SAT solvers. This paper presents a survey of the latest developments in SAT-based formal verification, including incomplete methods such as bounded model checking and complete methods for model checking. We focus on how the surveyed techniques formulate the verification problem as a SAT problem and how they exploit crucial aspects of a SAT solver, such as application-specific heuristics and conflict-driven learning. Finally, we summarize the noteworthy achievements in this area so far and note the major challenges in making this technology more pervasive in industrial design verification flows.
294 citations
TL;DR: This paper provides a survey on the recent development in level set methods in inverse problems and optimal design, and provides a review on numerical methods important in this context, and gives an overview of applications treated withlevel set methods.
Abstract: The aim of this paper is to provide a survey on the recent development in level set methods in inverse problems and optimal design. We give introductions on the general features of such problems involving geometries and on the general framework of the level set method. In subsequent parts we discuss shape sensitivity analysis and its relation to level set methods, various approaches on constructing optimization algorithms based on the level set approach, and special tools needed for the application of level set based optimization methods to ill-posed problems. Furthermore, we provide a review on numerical methods important in this context, and give an overview of applications treated with level set methods. Finally, we provide a discussion of the most challenging and interesting open problems in this field, that might be of interest for scientists who plan to start future research in this field.
291 citations
TL;DR: The results suggest that surfaces of toluene cast films exhibit a morphologically controlled hindrance for electron propagation toward the cathode, which is usually evaporated on top of the films in the solar cell device configuration.
Abstract: We conducted a comprehensive Kelvin probe force microscopy (KPFM) study on a classical organic solar cell system consisting of MDMO-PPV/PCBM blends. The KPFM method yields the information of topography and local work function at the nanometer scale. Experiments were performed either in the dark or under cw laser illumination at 442 nm. We identified distinct differences in the energetics on the surface of chlorobenzene and toluene cast blend films. Together with high-resolution scanning electron microscopy (SEM) experiments we were able to interpret the KPFM results and to draw some conclusions for the electron transport toward the cathode in the solar cell configuration. The results suggest that surfaces of toluene cast films exhibit a morphologically controlled hindrance for electron propagation toward the cathode, which is usually evaporated on top of the films in the solar cell device configuration.
TL;DR: In this article, the authors investigated the temperature and electric-field dependence of charge carrier mobility using a conventional time-of-flight technique in chemically purified, low-dark conductivity samples of regioregular poly(3-hexylthiophene) and showed that the mobility of doping-induced charge carriers correspond well to each other at temperatures above $130.
Abstract: The temperature and electric-field dependence of charge carrier mobility has been studied by a conventional time-of-flight technique in chemically purified, low dark conductivity samples of regioregular poly(3-hexylthiophene) Subsequently, the mobility of doping-induced charge carriers has been determined using the technique of charge carrier extraction by linearly increasing voltage in the same samples exposed to air The charge carrier mobility determined by both experimental techniques correspond well to each other at temperatures above $130\phantom{\rule{03em}{0ex}}\mathrm{K}$, indicating that these experimental techniques are mutually consistent The study clearly shows that the typical $\mathrm{log}\phantom{\rule{02em}{0ex}}\ensuremath{\mu}\ensuremath{\propto}\ensuremath{\beta}{E}^{1∕2}$, $\ensuremath{\beta}g0$ Poole--Frenkel-like electric-field dependence of the charge carrier mobility diminishes at temperatures around $250--270\phantom{\rule{03em}{0ex}}\mathrm{K}$, and $\ensuremath{\beta}$ becomes negative at higher temperatures Such negative electric-field dependence of mobility observed by both experimental techniques is attributed to positional disorder in a random-organic dielectric and analyzed in the framework of the disorder formalism Finally, the overall agreement indicates that the mode of charge generation has negligible effect on the temperature- and electric-field dependence of mobility except at the lowest temperatures $(l110\phantom{\rule{03em}{0ex}}\mathrm{K})$, where transit time dispersion of the photogenerated charge carriers probed by the ToF technique is more pronounced
TL;DR: In this paper, the morphology of polymer-fullerene blend films was investigated using poly(3-hexylthiophene)====== (P3HT) as the polymer and C61-butyric acid methyl ester (PCBM) or the newly synthesized polymerizable fullerene derivative, C61butyrous acid glycidol ester, PCBG, as the acceptor molecule, respectively.
Abstract: The morphological stabilization of donor–acceptor blends for bulk heterojunction solar cells can be achieved by cross-linking of the small molecular phase in the polymer matrix using a polymerizable fullerene derivative. In a comparative study the morphology of polymer–fullerene blend films was investigated using poly(3-hexylthiophene)
(P3HT) as the polymer and C61-butyric acid methyl ester (PCBM) or the newly synthesized polymerizable fullerene derivative, C61-butyric acid glycidol ester, PCBG, as the acceptor molecule, respectively. Changes in the nanomorphology due to heat treatment of the films were studied by means of atomic force microscopy (AFM), transmission electron microscopy (TEM) and photoluminescence (PL) studies. The polymerization process was monitored with infrared absorption studies. As demonstrated by these comparative studies this newly synthesized fullerene gives considerable stabilization of the solid state morphology in these blends. Such prevention of the long term, high temperature instability of bulk heterojunction morphology displays an important route to increase the operational stability of plastic solar cells in future applications.
TL;DR: In this paper, a model based on a dispersive bimolecular recombination is formulated, which properly describes the concentration decay of the extracted charge carriers at all measured temperatures and concentrations.
Abstract: Time-dependent mobility and recombination in the blend of poly[2-methoxy-5-(3,7-dimethyloctyloxy)-phenylene vinylene] (MDMO-PPV) and 1-(3-methoxycarbonyl)propyl-1-phenyl-(6,6)-${\mathrm{C}}_{61}$(PCBM) is studied simultaneously using the photoinduced charge carrier extraction by linearly increasing voltage technique. The charge carriers are photogenerated by a strongly absorbed, 3 ns laser flash, and extracted by the application of a reverse bias voltage pulse after an adjustable delay time $({t}_{\mathrm{del}})$. It is found that the mobility of the extracted charge carriers decreases with increasing delay time, especially shortly after photoexcitation. The time-dependent mobility $\ensuremath{\mu}(t)$ is attributed to the energy relaxation of the charge carriers towards the tail states of the density of states distribution. A model based on a dispersive bimolecular recombination is formulated, which properly describes the concentration decay of the extracted charge carriers at all measured temperatures and concentrations. The calculated bimolecular recombination coefficient $\ensuremath{\beta}(t)$ is also found to be time-dependent exhibiting a power law dependence as $\ensuremath{\beta}(t)={\ensuremath{\beta}}_{0}{t}^{\ensuremath{-}(1\ensuremath{-}\ensuremath{\gamma})}$ with increasing slope $(1\ensuremath{-}\ensuremath{\gamma})$ with decreasing temperatures. The temperature dependence study reveals that both the mobility and recombination of the photogenerated charge carriers are thermally activated processes with activation energy in the range of 0.1 eV. Finally, the direct comparison of $\ensuremath{\mu}(t)$ and $\ensuremath{\beta}(t)$ shows that the recombination of the long-lived charge carriers is controlled by diffusion.
TL;DR: In this paper, the authors investigated the stability and convergence of local volatility surfaces σ(S, t) in the Black-Scholes/Dupire equation from market prices of European Vanilla options.
Abstract: This paper investigates the stable identification of local volatility surfaces σ(S, t) in the Black–Scholes/Dupire equation from market prices of European Vanilla options. Based on the properties of the parameter-to-solution mapping, which assigns option prices to given volatilities, we show stability and convergence of approximations gained by Tikhonov regularization. In the case of a known term-structure of the volatility surface, in particular, if the volatility is assumed to be constant in time, we prove convergence rates under simple smoothness and decay conditions on the true volatility. The convergence rate analysis sheds light onto the importance of an appropriate a priori guess for the unknown volatility and the nature of the ill-posedness of the inverse problem, caused by smoothing properties and the nonlinearity of the direct problem. Finally, the theoretical results are illustrated by numerical experiments.
TL;DR: An overview is provided on the preparation of cellular polymers by physical foaming, on their charging by "microstorms", on their piezo- and pyroelectricity, and on analogies to ferroelectrics.
Abstract: Cellular polymers can be internally charged by "microstorms" (silent or partial discharges) within the voids of the polymer foam. The resulting material, which carries positive and negative charges on the internal void surfaces, is called a ferroelectret. Ferroelectrets behave like typical ferroelectrics, hence they provide a novel class of ferroic materials. The soft foams are strongly piezoelectric and can be used, in a wide range of applications, as transducers for interconverting mechanical and electrical signals. Herein, an overview is provided on the preparation of cellular polymers by physical foaming (extrusion, biaxial stretching, and controlled inflation by pressure treatments), on their charging by "microstorms", on their piezo- and pyroelectricity, and on analogies to ferroelectrics. Finally, a survey of selected applications is presented.
18 Jul 2005
TL;DR: Based on the semiconducting properties of organic conjugated macromolecules, these devices possess the potential to be processed by common printing techniques and open the route of roll-to-roll production of low cost renewable energy sources.
Abstract: Triggered by the outstanding worldwide growth of the photovoltaic market as well as by the need of alternative energy sources in future, organic solar cells are the object of vivid interest from both industrial and academic sides. Based on the semiconducting properties of organic conjugated macromolecules, these devices possess the potential to be processed by common printing techniques. Besides being easily upscalable on rigid as well as on flexible substrates, they open the route of roll-to-roll production of low cost renewable energy sources. Today, up to 5% power conversion efficiencies are reported in this kind of plastic solar cells.
01 Jun 2005-Compel-the International Journal for Computation and Mathematics in Electrical and Electronic Engineering
TL;DR: In this article, a hierarchical H(curl)conforming finite elements for triangular and tetrahedral element geometries is presented. But the shape functions are classified as lowest order Nedelec, higher order edge-based, face-based and element-based.
Abstract: Purpose – The goal of the presented work is the efficient computation of Maxwell boundary and eigenvalue problems using high order H(curl) finite elements.Design/methodology/approach – Discusses a systematic strategy for the realization of arbitrary order hierarchic H(curl)‐conforming finite elements for triangular and tetrahedral element geometries. The shape functions are classified as lowest order Nedelec, higher‐order edge‐based, face‐based (only in 3D) and element‐based ones.Findings – Our new shape functions provide not only the global complete sequence property but also local complete sequence properties for each edge‐, face‐, and element‐block. This local property allows an arbitrary variable choice of the polynomial degree for each edge, face, and element. A second advantage of this construction is that simple block‐diagonal preconditioning gets efficient. Our high order shape functions contain gradient shape functions explicitly. In the case of a magnetostatic boundary value problem, the gradien...
TL;DR: It can be concluded that awareness addresses different constellations of group settings, different types of individual behavior, and different contexts of use, which should help to achieve a shift from technology-driven development toward human-centered design of collaborative communities.
Abstract: An increasing number of computer-supported cooperative work (CSCW) software systems try to provide users with awareness information-information about the presence, activities, and availability of members of a community. However, most of these software systems are designed from a feature-oriented, rather than a human-oriented, point of view. In this article, a structured embedding of findings in social sciences is proposed. It reveals the variety of approaches in technology-driven CSCW developments featuring awareness, as well as the variety of empirical evidence in small-group research with respect to awareness. The authors have been looking at different aspects of awareness: the terminology used in both disciplines, the concepts that have been developed, and the different constructs that have evolved from empirical research. Finally, operational instances of awareness have been revisited. From these findings it can be concluded that awareness addresses different constellations of group settings, differen...
TL;DR: In this paper, a shelf lifetime study performed by encapsulating the cells in a flexible and transparent gas barrier material was performed, and a new approach was proposed to pattern organic solar cells and design large-scale modules.
Abstract: Organic solar cells based on conjugated polymer:fullerene blends show nowadays efficiencies above 4%. After briefly presenting the science of bulk-heterojunction solar cells, we report herein a shelf lifetime study performed by encapsulating the cells in a flexible and transparent gas barrier material. This method allows lifetimes as reported for glass encapsulation. Moreover, we propose a new approach to pattern organic solar cells and design large-scale modules. This technique, based on selective Nd:yttrium aluminum garnet (YAG) laser etching, potentially enables low-cost, high-speed roll-to-roll operation.
Proceedings Article•
01 Jan 2005TL;DR: MATCH, a toolkit for aligning audio recordings of different renditions of the same piece of music, based on an efficient implementation of a dynamic time warping algorithm, which can be used in real time for tracking live performances.
Abstract: We present MATCH, a toolkit for aligning audio recordings of different renditions of the same piece of music, based on an efficient implementation of a dynamic time warping algorithm. A forward path estimation algorithm constrains the alignment path so that dynamic time warping can be performed with time and space costs that are linear in the size of the audio files. Frames of audio are represented by a positive spectral difference vector, which emphasises note onsets in the alignment process. In tests with Classical and Romantic piano music, the average alignment error was 41ms (median 20ms), with only 2 out of 683 test cases failing to align. The software is useful for content-based indexing of audio files and for the study of performance interpretation; it can also be used in real-time for tracking live performances. The toolkit also provides functions for displaying the cost matrix, the forward and backward paths, and any metadata associated with the recordings, which can be shown in real time as the alignment is computed.
TL;DR: In this article, the authors identify several areas in which the existence of the hard-to-tax may have significant economic effects, and provide various informed, if only suggestive, estimates of the size of these impacts; that is, they focus on "sizing" the problem of the HTT.
Abstract: This paper analyzes the hard-to-tax, asking the basic question: Why should the HTT matter to policy makers? In particular, we identify several areas in which we believe that the existence of the HTT may have significant economic effects, and we attempt to provide various informed, if only suggestive, estimates of the size of these impacts; that is, we focus on ‘sizing’ the problem of the HTT. We find that the HTT can have a significant impact on tax revenues, especially for developing countries. We also find that a larger HTT sector leads to a greater reliance in tax structures on indirect taxation. The hard-to-tax seem to be associated with an array of welfare losses driven by the induced misallocation of resources, and these excess burdens can be quite large. The role of the HTT on long run economic development appears to be quite diverse; a larger size of the HTT tends to slow down economic growth in developing countries but it accelerates it in industrialized countries. Finally, we find that the impact of the hard-to-tax on equity is complicated by the final incidence of the forms of tax evasion represented by the hard-to-tax. Nevertheless, even though it may often be the case that HTT groups do not benefit directly from evasion because of the final incidence of this form of tax evasion, it seems uncontroversial that having the hard-to-tax pay their fair share of taxes will improve the overall equity of the tax system.
TL;DR: This paper showed that in a country (Austria) where consumers speak a different language with very different cultural heritage, the use of a foreign celebrity and an English brand name can be a liability.
Abstract: Whereas most recent country-of-origin (COO) research has focused on multi-cue designs to overcome weaknesses associated with single-cue models by incorporating both extrinsic and intrinsic cues other than the COO cue in evaluating consumer responses, few studies have been reported that address the issue of whether a foreign celebrity or a foreign brand name can enhance or diminish consumer attitude, product quality perception and purchase intention in another country. This study shows that in a country (Austria) where consumers speak a different language with very different cultural heritage, the use of a foreign (US) celebrity and an English brand name can be a liability. Consumer ethnocentrism is a plausible explanation for this observation.
TL;DR: In this article, C60-based n-channel organic field effect transistors with mobility in the range of 4-1-cm2-V−1-s−1 were presented.
TL;DR: In this paper, the authors compare the exciton dissociation and geminate charge recombination dynamics in blends of two conjugated polymers, MeLPPP and MDMO-PPV, with the electron accepting fullerene derivative PCBM.
Abstract: We investigate the nature of ultrafast exciton dissociation and carrier generation in acceptor-doped conjugated polymers. Using a combination of two-pulse femtosecond spectroscopy with photocurrent detection, we compare the exciton dissociation and geminate charge recombination dynamics in blends of two conjugated polymers, MeLPPP [methyl-substituted ladder-type poly($p$-phenylene)] and MDMO-PPV [poly(2-methoxy,5-(3,7-dimethyloctyloxy)-1,4-phenylenevinylene], with the electron accepting fullerene derivative PCBM [1-(3-methoxycarbonyl)-propyl-1-phenyl-$(6,6){\mathrm{C}}_{61}$]. This technique allows us to distinguish between free charge carriers and Coulombically bound polaron pairs. Our results highlight the importance of geminate pair recombination in photovoltaic devices, which limits the device performance. The comparison of different materials allows us to address the dependence of geminate recombination on the film morphology directly at the polymer:fullerene interface. We find that in the MeLPPP:PCBM blend exciton dissociation generates Coulombically bound geminate polaron pairs with a high probability for recombination, which explains the low photocurrent yield found in these samples. In contrast, in the highly efficient MDMO-PPV:PCBM blend the electron transfer leads to the formation of free carriers. The anisotropy dynamics of electronic transitions from neutral and charged states indicate that polarons in MDMO-PPV relax to delocalized states in ordered domains within $500\phantom{\rule{0.3em}{0ex}}\mathrm{fs}$. The results suggest that this relaxation enlarges the distance of carrier separation within the geminate pair, lowering its binding energy and favoring full dissociation. The difference in geminate pair recombination concurs with distinct dissociation dynamics. The electron transfer is preceded by exciton migration towards the PCBM sites. In MeLPPP:PCBM the exciton migration time decays smoothly with increasing PCBM concentration, indicating a trap-free exciton hopping. In MDMO-PPV:PCBM, however, the exciton migration time is found to show a threshold-like dependence on the PCBM concentration. This observation is explained by efficient interchain energy transfer in ordered MDMO-PPV domains in conjunction with exciton trapping.
TL;DR: The authors examined citizens' attitudes toward paying taxes and found that a lower perceived compliance leads to a decrease of tax morale, which indicates that social comparisons are relevant and showed that tax morale may be a key determinant to explain why people are honest.
Abstract: People mostly pay their taxes although there is a low probability of getting caught and being penalized. Thus, new attempts in the tax compliance literature try to go beyond standard economic theory. This paper examines citizens’ attitudes toward paying taxes – what is sometimes termed their “tax morale”, or the intrinsic motivation to pay taxes. Tax morale may be a key determinant to explain why people are honest. However, there are very few papers that explore the concept of tax morale theoretically and empirically. This study, based on the World Values Survey and the European Values Survey, therefore attempts to fill this gap in the literature, focusing on tax morale in Austria. Societal variables such as trust or pride have been identified as key determinants that shape tax morale in Austria. Furthermore, a lower perceived compliance leads to a decrease of tax morale, which indicates that social comparisons are relevant. The results also show a decrease of tax morale between 1990 and 1999, although Austria’s taxpayers still have a very high tax morale compared to other European countries.
TL;DR: A method for the determination of the major components of (methoxymethyl)melamine resins, with quantitative analysis of unreacted melamine by capillary zone electrophoresis (CZE) using electrospray ionization‐mass spectrometry (ESI‐MS).
Abstract: A method for the determination of the major components of (methoxymethyl)melamine resins, with quantitative analysis of unreacted melamine by capillary zone electrophoresis (CZE) using electrospray ionization-mass spectrometry (ESI-MS) is presented. Using a low background electrolyte (BGE) pH, components are separated according to their charge/ionic radius ratio with a distinctly different separation selectivity compared to the HPLC methods commonly employed in melamine-resin analysis. The use of a time-of-flight mass spectrometer (TOF-MS) was concluded to be necessary, as the complex samples studied required maximum sensitivity and resolution, which is clearly superior for TOF-MS detectors over their quadrupole counterparts. A standard curve of free melamine was determined with an R(2) = 0.999 over a concentration range of an order of magnitude. This method offers the unique separation selectivity of CZE as well as a quicker analysis time, especially for dimers compared to the HPLC methods used to date.
TL;DR: In this paper, the authors provide the first known estimates of the shadow economy for 17 Asia-Pacific countries and show that not only have these activities grown over the last ten years, but countries with relatively thin taxpayer compliance initiatives experience the greatest shadow economy activity.
Abstract: . Despite continuous government attempts to increase taxpayer compliance, the shadow economy continues to offer a way for taxpayers to evade their taxpaying obligations. The consequences are clear: policy-makers have increasingly imperfect knowledge about the state of economic affairs as shadow economy activity expands. We provide the first known estimates of the shadow economy for 17 Asia-Pacific countries. We show that, not only have these activities grown over the last ten years, but countries with relatively thin taxpayer compliance initiatives experience the greatest shadow economy activity.
TL;DR: In this article, the authors investigated the correlation chain from the polymer structure to the final application properties of propylene-ethylene random copolymers, four commercial grades with different ethylene content (0, 8 mol %) but identical molecular weight distributions were investigated.
Abstract: For understanding the correlation chain from the polymer structure to the final application properties of propylene–ethylene random copolymers, four commercial grades with different ethylene content (0–8 mol %) but identical molecular weight distributions were investigated. Structural investigations concerning the comonomer distribution, using two different techniques (temperature rising elution fractionation and stepwise isothermal segregation), showed an increase of inhomogeneity with the total comonomer content, which was reflected for temperature rising elution fractionation in a widening of the elution temperature range. Crystallinity and crystallization speed studies confirmed the reduced overall crystallinity and increase of γ-modification content as reported previously, but they also showed the reason for these effects in the distinctive decrease of the spherulitic growth speed. Good correlations of all these parameters to the mechanical performance of the four materials were obtained. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1073–1081, 2005