Showing papers by "Eindhoven University of Technology published in 2004"
TL;DR: In this paper, the authors make four contributions to the approach by addressing some open issues in the sectoral systems of innovation (SOSI) approach, namely, explicitly incorporating the user side in the analysis, suggesting an analytical distinction between systems, actors involved in them, and the institutions which guide actor perceptions and activities.
3,221 citations
TL;DR: A new algorithm is presented to extract a process model from a so-called "workflow log" containing information about the workflow process as it is actually being executed and represent it in terms of a Petri net.
Abstract: Contemporary workflow management systems are driven by explicit process models, i.e., a completely specified workflow design is required in order to enact a given workflow process. Creating a workflow design is a complicated time-consuming process and, typically, there are discrepancies between the actual workflow processes and the processes as perceived by the management. Therefore, we have developed techniques for discovering workflow models. The starting point for such techniques is a so-called "workflow log" containing information about the workflow process as it is actually being executed. We present a new algorithm to extract a process model from such a log and represent it in terms of a Petri net. However, we also demonstrate that it is not possible to discover arbitrary workflow processes. We explore a class of workflow processes that can be discovered. We show that the /spl alpha/-algorithm can successfully mine any workflow represented by a so-called SWF-net.
1,953 citations
TL;DR: Inkjet printing is considered to be a key technology in the field of defined polymer deposition as mentioned in this paper, and a short overview of the available instrumentation is given, including manufacturing of multicolor polymer light-emitting diode displays, polymer electronics, three-dimensional printing, and oral dosage forms for controlled drug release.
Abstract: Inkjet printing is considered to be a key technology in the field of defined polymer deposition. This article provides an introduction to inkjet printing technology and a short overview of the available instrumentation. Examples of polymer inkjet printing are given, including the manufacturing of multicolor polymer light-emitting diode displays, polymer electronics, three-dimensional printing, and oral dosage forms for controlled drug release. Special emphasis is placed upon the utilized polymers and conditions, such as polymer structure, molar mass, solvents, and concentration. Studies on viscoelastic fluid jets and the formation of viscoelastic droplets under gravity indicate that strain hardening is the key parameter that determines the inkjet printability of polymer solutions.
1,808 citations
TL;DR: A laser accelerator that produces electron beams with an energy spread of a few per cent, low emittance and increased energy (more than 109 electrons above 80 MeV) and opens the way for compact and tunable high-brightness sources of electrons and radiation.
Abstract: Laser-driven accelerators, in which particles are accelerated by the electric field of a plasma wave (the wakefield) driven by an intense laser, have demonstrated accelerating electric fields of hundreds of GV m-1 (refs 1–3) These fields are thousands of times greater than those achievable in conventional radio-frequency accelerators, spurring interest in laser accelerators4,5 as compact next-generation sources of energetic electrons and radiation To date, however, acceleration distances have been severely limited by the lack of a controllable method for extending the propagation distance of the focused laser pulse The ensuing short acceleration distance results in low-energy beams with 100 per cent electron energy spread1,2,3, which limits potential applications Here we demonstrate a laser accelerator that produces electron beams with an energy spread of a few per cent, low emittance and increased energy (more than 109 electrons above 80 MeV) Our technique involves the use of a preformed plasma density channel to guide a relativistically intense laser, resulting in a longer propagation distance The results open the way for compact and tunable high-brightness sources of electrons and radiation
1,749 citations
TL;DR: In this article, the authors argue that management theory stands a better chance of being adopted for instrumental use if the theory is based on the paradigm of the "design sciences" like medicine or engineering, and they discuss the potential of solving its utility problem by combining both types of research.
Abstract: Academic management theory has a serious utilization problem. This article argues that it stands a better chance of being adopted for instrumental use if the theory is based on the paradigm of the “design sciences”, like medicine or engineering. Most academic management research is based on the paradigm of the “explanatory sciences”, like physics. The mission of these sciences is to describe, explain and predict, while the core mission of the design sciences is to develop “tested and grounded technological rules”. The paradigm of the design sciences is applied to management research and I discuss the potential of solving its utility problem by combining both types of research.
1,382 citations
TL;DR: A new algorithm for digital inpainting based on the fast marching method for level set applications is presented, very simple to implement, fast, and produces nearly identical results to more complex, and usually slower, known methods.
Abstract: Digital inpainting provides a means for reconstruction of small damaged portions of an image. Although the inpainting basics are straightforward, most inpainting techniques published in the literature are complex to understand and implement. We present here a new algorithm for digital inpainting based on the fast marching method for level set applications. Our algorithm is very simple to implement, fast, and produces nearly identical results to more complex, and usually slower, known methods. Source code is available online.
1,109 citations
TL;DR: In this article, an eddy-viscosity model is proposed and applied in large-eddy simulation of turbulent shear flows with quite satisfactory results, which is essentially not more complicated than the Smagorinsky model, but is constructed in such a way that its dissipation is relatively small in transitional and near-wall regions.
Abstract: An eddy-viscosity model is proposed and applied in large-eddy simulation of turbulent shear flows with quite satisfactory results. The model is essentially not more complicated than the Smagorinsky model, but is constructed in such a way that its dissipation is relatively small in transitional and near-wall regions. The model is expressed in first-order derivatives, does not involve explicit filtering, averaging, or clipping procedures, and is rotationally invariant for isotropic filter widths. Because of these highly desirable properties the model seems to be well suited for engineering applications. In order to provide a foundation of the model, an algebraic framework for general three-dimensional flows is introduced. Within this framework several types of flows are proven to have zero energy transfer to subgrid scales. The eddy viscosity is zero in the same cases; the theoretical subgrid dissipation and the eddy viscosity have the same algebraic structure. In addition, the model is based on a fundament...
1,003 citations
TL;DR: In this article, an efficient bulk-heterojunction solar cells can be made using ZnO nanoparticles and a conjugated polymer, and the incident photon to current conversion efficiency (IPCE) closely resembles the absorption spectrum of the MDMO-PPV layer on glass, and reaches a value of 40 % at the absorption max.
Abstract: The authors show that efficient bulk-heterojunction solar cells can be made using ZnO nanoparticles and a conjugated polymer. These cells can be processed from soln. and exhibit an incident photon to current conversion efficiency up to 40 %. Nanocryst. ZnO (nc-ZnO) of approx. 5 nm diam. was synthesized and used. As the n-type semiconductor. Complexes with MDMO-PPV were used, with Aluminum and a PEDOT-PSS/ITO-coated glass hole-conducting electrode. The incident photon to current conversion efficiency (IPCE)closely resembles the absorption spectrum of the MDMO-PPV:nc-ZnO layer on glass, and reaches a value of 40 % at the absorption max. MDMO-PPV. Integration of this spectral response with the solar spectrum (AM1.5G, normalized 100 mW cm-2) affords an est. of the short-circuit c.d. of Jsc = 3.3 mA/cm2 under AM1.5 (1 sun) conditions. C.d.-voltage (J-V) measurements, carried out in the dark reveal excellent diode behavior, with electron current dominating the c.d. in forward bias. TEM micrographs showed intimate mixing of the ZnO and the MDMO-PPV, with the majority of the polymer domains smaller than a few tens of nanometers, which has been shown to be the exciton diffusion length in a similar PPV polymer.
920 citations
TL;DR: In this paper, the authors explore heterogeneities in the determinants of innovating firms' decisions to engage in R&D cooperation, differentiating between four types of cooperation partners: competitors, suppliers, customers, and universities and research institutes.
710 citations
TL;DR: This critical review describes recent developments in the field of supramolecular chemistry of terpyridine-metal complexes and places a special emphasis upon the properties of functional systems.
Abstract: This critical review describes recent developments in the field of supramolecular chemistry of terpyridine–metal complexes. The synthesis and characteristics of single as well as multiple homo- and heterometallic complexes is discussed. Furthermore, complexes containing fullerenes, biological building blocks, extended aggregates of different architectures as well as rings are presented. A special emphasis is placed upon the properties (e.g. redox properties, luminescence etc.) of functional systems. Potential applications in optical nano-devices, molecular storage units, molecular switches and solar cells are discussed.
681 citations
TL;DR: In this article, a combination of techniques was used to resolve the morphology of spin cast films of poly(p-phenylene vinylene)/methanofullerene blends in three dimensions on a nanometer scale and relate the results to the performance of the corresponding solar cells.
Abstract: The performance of bulk-heterojunction solar cells based on a phase-separated mixture of donor and acceptor materials is known to be critically dependent on the morphology of the active layer. Here we use a combination of techniques to resolve the morphology of spin cast films of poly(p-phenylene vinylene)/methanofullerene blends in three dimensions on a nanometer scale and relate the results to the performance of the corresponding solar cells. Atomic force microscopy (AFM), transmission electron microscopy (TEM), and depth profiling using dynamic time-of-flight secondary ion mass spectrometry (TOF-SIMS) clearly show that for the two materials used in this study, 1-(3-methoxycarbonyl)propyl-1-phenyl-[6,6]-methanofullerene (PCBM) and poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylene vinylene] (MDMO-PPV), phase separation is not observed up to 50 wt.-% PCBM. Nanoscale phase separation throughout the film sets in for concentrations of more than 67 wt.-% PCBM, to give domains of rather pure PCBM in a homogenous matrix of 50:50 wt.-% MDMO-PPV/PCBM. Electrical characterization, under illumination and in the dark, of the corresponding photovoltaic devices revealed a strong increase of power conversion efficiency when the phase-separated network develops, with a sharp increase of the photocurrent and fill factor between 50 and 67 wt.-% PCBM. As the phase separation sets in, enhanced electron transport and a reduction of bimolecular charge recombination provide the conditions for improved performance. The results are interpreted in terms of a model that proposes a hierarchical build up of two cooperative interpenetrating networks at different length scales.
TL;DR: The topic of process mining is put into context, the main issues around process mining are discussed, and the papers in this special issue are introduced.
TL;DR: Albatross as mentioned in this paper is a learning-based transportation-oriented simulation system that predicts which activities are conducted when, where, for how long, with whom, and the transport mode involved.
Abstract: This paper describes the conceptual development, operatonalization and empirical testing of Albatross: A Learning-based Transportation Oriented Simulation System. This activity-based model of activity-travel behavior is derived from theories of choice heuristics that consumers apply when making decisions in complex environments. The model, one of the most comprehensive of its kind, predicts which activities are conducted when, where, for how long, with whom, and the transport mode involved. In addition, various situational, temporal, spatial, spatial-temporal and institutional constraints are incorporated in the model. The decision tree is proposed as a formalism to represent an exhaustive set of mutually exclusive rules for each decision step in the model. A CHAID decision tree induction method is used to derive decision trees from activity diary data. The case study conducted to develop and test the model indicates that performance of the model is very satisfactory. We conclude therefore that the methodology proposed in this article is useful to develop computational process models of activity-travel choice behavior.
TL;DR: Simulations show that the ring lasers with extremely small size and low operating power presented here have the potential for much smaller dimensions and switching times, and large numbers of such memory elements can be densely integrated and interconnected on a photonic integrated circuit.
Abstract: The increasing speed of fibre-optic-based telecommunications has focused attention on high-speed optical processing of digital information1. Complex optical processing requires a high-density, high-speed, low-power optical memory that can be integrated with planar semiconductor technology for buffering of decisions and telecommunication data2. Recently, ring lasers with extremely small size and low operating power have been made3,4,5,6,7, and we demonstrate here a memory element constructed by interconnecting these microscopic lasers. Our device occupies an area of 18 × 40 µm2 on an InP/InGaAsP photonic integrated circuit, and switches within 20 ps with 5.5 fJ optical switching energy. Simulations show that the element has the potential for much smaller dimensions and switching times. Large numbers of such memory elements can be densely integrated and interconnected on a photonic integrated circuit: fast digital optical information processing systems employing large-scale integration should now be viable.
TL;DR: In this paper, a questionnaire consisting of three environmental knowledge scales and a conservation behavior measure was sent to 5000 randomly selected Swiss adults. A completed questionnaire was returned by 55% of them (N=2736).
TL;DR: In this paper, a second-order computational homogenization approach is applied for the multi-scale analysis of simple shear of a constrained heterogeneous strip, where a pronounced boundary size effect appears.
TL;DR: In this paper, the authors investigated the structural relationship among market orientation, new product advantage, the proficiency in new product launch activities, and organizational performance and found that market orientation is related positively to product advantage and to the proficiency of market testing, launch budgeting, launch strategy, and launch tactics.
TL;DR: The findings suggest that developing PMSs should to a large extent be understood as a co-ordination effort rather than a design effort and the lessons learned cannot have universal validity, but may be helpful in similar kinds of initiatives.
TL;DR: The formation of ring stains are eliminated by printing nonvolatile acetophenone-based inks on a perfluorinated substrate using different polymers, andrays of closely spaced dots have also been printed.
Abstract: Inkjet printing represents a highly promising polymer deposition method, which is used for, for example, the fabrication of multicolor polyLED displays and polymer-based electronics parts. The challenge is to print well-defined polymer structures from dilute solution. We have eliminated the formation of ring stains by printing nonvolatile acetophenone-based inks on a perfluorinated substrate using different polymers. (De)pinning of the contact line of the printed droplet, as related to the choice of solvent, is identified as the key factor that determines the shape of the deposit, whereas the choice of polymer is of minor importance. Adding 10 wt % or more of acetophenone to a volatile solvent (ethyl acetate)-based polymer solution changes the shape of the deposit from ring-like to dot-like, which may be due to the establishment of a solvent composition gradient. Arrays of closely spaced dots have also been printed. The size of the dots is considerably smaller than the nozzle diameter. This may prove a potential strategy for the inkjet printing of submicrometer structures.
TL;DR: The complete MIMO OFDM processing is implemented in a system with three transmit and three receive antennas, and its performance is evaluated with both simulations and experimental test results.
Abstract: The combination of multiple-input multiple-output (MIMO) signal processing with orthogonal frequency division multiplexing (OFDM) is regarded as a promising solution for enhancing the data rates of next-generation wireless communication systems operating in frequency-selective fading environments. To realize this extension of OFDM with MIMO, a number of changes are required in the baseband signal processing. An overview is given of the necessary changes, including time and frequency synchronization, channel estimation, synchronization tracking, and MIMO detection. As a test case, the OFDM-based wireless local area network (WLAN) standard IEEE 802.11a is considered, but the results are applicable more generally. The complete MIMO OFDM processing is implemented in a system with three transmit and three receive antennas, and its performance is evaluated with both simulations and experimental test results. Results from measurements with this MIMO OFDM system in a typical office environment show, on average, a doubling of the system throughput, compared with a single antenna OFDM system. An average expected tripling of the throughput was most likely not achieved due to coupling between the transmitter and receiver branches.
TL;DR: In this article, a review of microwave systems and their applications in polymer syntheses is presented, covering step-growth and ring-opening, as well as radical polymerization processes, in order to summarize the hitherto realized polymerizations.
Abstract: Monomodal microwaves have overcome the safety uncertainties associated with the precedent domestic microwave ovens. After fast acceptance in inorganic and organic syntheses, polymer chemists have also recently discovered this new kind of microwave reactor. An almost exponential increase of the number of publications in this field reflects the steadily growing interest in the use of microwave irradiation for polymerizations. This review introduces the microwave systems and their applications in polymer syntheses, covering step-growth and ring-opening, as well as radical polymerization processes, in order to summarize the hitherto realized polymerizations. Special attention is paid to the differences between microwave-assisted and conventional heating as well as the microwave effects.
01 Jan 2004
TL;DR: The effectiveness of the MPE method is demonstrated by applying it to a nonlinear computational fluid dynamic model of an industrial glass furnace and the Galerkin projection can be computed using only 25% of the spatial grid points without compromising the accuracy of the reduced model.
Abstract: This paper presents a new method of missing point estimation (MPE) to derive efficient reduced-order models for large-scale parameter-varying systems. Such systems often result from the discretization of nonlinear partial differential equations. A projection-based model reduction framework is used where projection spaces are inferred from proper orthogonal decompositions of data-dependent correlation operators. The key contribution of the MPE method is to perform online computations efficiently by computing Galerkin projections over a restricted subset of the spatial domain. Quantitative criteria for optimally selecting such a spatial subset are proposed and the resulting optimization problem is solved using an efficient heuristic method. The effectiveness of the MPE method is demonstrated by applying it to a nonlinear computational fluid dynamic model of an industrial glass furnace. For this example, the Galerkin projection can be computed using only 25% of the spatial grid points without compromising the accuracy of the reduced model.
TL;DR: In this article, the heat flux method for stabilizing flat adiabatic flames and measuring adibatic burning velocities is reviewed and the latest improvements of the burner construction and analysis of the measurements are presented.
TL;DR: The well-defined co-aggregated dyes presented here exhibit photoinduced electron transfer on subpicosecond time scale, and thus, these supramolecular entities might serve as valuable nanoscopic functional units.
Abstract: Comparative studies on hydrogen-bonded versus covalently linked donor-acceptor-donor dye arrays obtained from oligo(p-phenylene vinylene)s (OPVs) as donor and bay-substituted perylene bisimides (PERYs) as acceptor dyes are presented. Both systems form well-ordered J-type aggregates in methylcyclohexane, but only hydrogen-bonded arrays afford hierarchically assembled chiral OPV-PERY dye superstructures consisting of left-handed helical pi-pi co-aggregates (CD spectroscopy) of the two dyes that further assemble into right-handed nanometer-scale supercoils in the solid state (AFM study). In the case of hydrogen-bonded arrays, the stability of the aggregates in solution increases with increasing conjugation length of the OPV unit. The well-defined co-aggregated dyes presented here exhibit photoinduced electron transfer on subpicosecond time scale, and thus, these supramolecular entities might serve as valuable nanoscopic functional units.
20 Sep 2004
TL;DR: A definition of social robots is proposed and a framework that classifies properties of social Robots is described, which consist of form, modality, social norms, autonomy, and interactivity.
Abstract: Robots currently integrate into our everyday lives, but little is known about how they can act socially. In this paper, we propose a definition of social robots and describe a framework that classifies properties of social robots. The properties consist of form, modality, social norms, autonomy, and interactivity. Finally, we provide broad guidelines for the design of social robots.
01 Jan 2004
TL;DR: The history of process algebra as an area of research in concurrency theory, the theory of parallel and distributed systems in computer science is discussed in this article, where the author gives his personal views on these matters.
Abstract: . This note addresses the history of process algebra as an area of research in concurrency theory, the theory of parallel and distributed systems in computer science. Origins are traced back to the early seventies of the twentieth century, and developments since that time are sketched. The author gives his personal views on these matters. He also considers the present situation, and states some challenges for the future.
TL;DR: In this article, the authors evaluated the propagation rate coefficients for free-radical polymerization of butyl acrylate (BA) using pulsed-laser polymerization and subsequent polymer analysis by size exclusion (SEC) chromatography.
Abstract: Summary: Propagation rate coefficients, kp, for free-radical polymerization of butyl acrylate (BA) previously reported by several groups are critically evaluated. All data were determined by the combination of pulsed-laser polymerization (PLP) and subsequent polymer analysis by size exclusion (SEC) chromatography. The PLP-SEC technique has been recommended as the method of choice for the determination of kp by the IUPAC Working Party on Modeling of Polymerization Kinetics and Processes. Application of the technique to acrylates has proven to be very difficult and, along with other experimental evidence, has led to the conclusion that acrylate chain-growth kinetics are complicated by intramolecular transfer (backbiting) events to form a mid-chain radical structure of lower reactivity. These mechanisms have a significant effect on acrylate polymerization rate even at low temperatures, and have limited the PLP-SEC determination of kp of chain-end radicals to low temperatures (<20 °C) using high pulse repetition rates. Nonetheless, the values for BA from six different laboratories, determined at ambient pressure in the temperature range of −65 to 20 °C mostly for bulk monomer with few data in solution, fulfill consistency criteria and show excellent agreement, and are therefore combined together into a benchmark data set. The data are fitted well by an Arrhenius relation resulting in a pre-exponential factor of 2.21 × 107 L · mol−1 · s−1 and an activation energy of 17.9 kJ · mol−1. It must be emphasized that these PLP-determined kp values are for monomer addition to a chain-end radical and that, even at low temperatures, it is necessary to consider the presence of two radical structures that have very different reactivity. Studies for other alkyl acrylates do not provide sufficient results to construct benchmark data sets, but indicate that the family behavior previously documented for alkyl methacrylates also holds true within the alkyl acrylate family of monomers.
Arrhenius plot of propagation rate coefficients, kp, for BA as measured by PLP-SEC.
TL;DR: In this article, composites consisting of individual, or bundles of single-walled, exfoliated nanotubes in a highly viscous polymer matrix (see Figure) are described.
Abstract: Composites consisting of individual, or bundles of single-walled, exfoliated nanotubes in a highly viscous polymer matrix (see Figure) are described. The nanotubes and polymer are made compatible using surfactant molecules, hence avoiding the need for direct attraction between the nanotubes and the matrix. The resulting nanotube-polymer composites have a conductivity percolation threshold of 0.28 wt.-% nanotubes.
TL;DR: In this article, the authors provided a framework that essentially requires measuring behavior more generally, based on a theory of goal-directed performance, and tested a set of 50 behaviors by simultaneously applying a one and a six-dimensional Rasch-type model.
TL;DR: In this paper, the authors compared the performance of Partial Least Squares (PLS) and Support Vector Machines (SVM) for two spectral regression applications and found that SVM outperformed PLS.