Showing papers by "Eindhoven University of Technology published in 2001"
TL;DR: From the protocol data, aspects of creativity in design related to the formulation of the design problem and to the concept of originality are identified and a model of creative design as the co-evolution of problem/solution spaces is applied, confirming the general validity of the model.
1,956 citations
TL;DR: A micro-macro strategy suitable for modeling the mechanical response of heterogeneous materials at large deformations and non-linear history dependent material behaviour is presented and its performance is illustrated by the simulation of pure bending of porous aluminum.
Abstract: A micro-macro strategy suitable for modeling the mechanical response of heterogeneous materials at large deformations and non-linear history dependent material behaviour is presented. When using this micro-macro approach within the context of finite element implementation there is no need to specify the homogenized constitutive behaviour at the macroscopic integration points. Instead, this behaviour is determined through the detailed modeling of the microstructure. The performance of the method is illustrated by the simulation of pure bending of porous aluminum. The influence of the spatial distribution of heterogeneities on the overall macroscopic behaviour is discussed by comparing the results of micro-macro modeling for regular and random structures.
848 citations
TL;DR: Equivalences among five classes of hybrid systems are established, of paramount importance for transferring theoretical properties and tools from one class to another, with the consequence that for the study of a particular hybrid system that belongs to any of these classes, one can choose the most convenient hybrid modeling framework.
780 citations
TL;DR: In this paper, the key size for symmetric cryptosystems, RSA, and discrete logarithm-based crypto-systems over finite fields and groups of elliptic curves over prime fields is discussed.
Abstract: In this article we offer guidelines for the determination of key sizes for symmetric cryptosystems, RSA, and discrete logarithm-based cryptosystems both over finite fields and over groups of elliptic curves over prime fields. Our recommendations are based on a set of explicitly formulated parameter settings, combined with existing data points about the cryptosystems.
769 citations
TL;DR: The chiral architectures from macromolecular building blocks were discussed and the conformational dynamics of the helicity and their effect on the physical properties of the polymers and the induction of helicity in the polymer chain were elaborated.
Abstract: The chiral architectures from macromolecular building blocks were discussed. The conformational dynamics of the helicity and their effect on the (photo)physical properties of the polymers and the induction of helicity in the polymer chain were elaborated. The influence of kinetics on the macromolecular secondary structure and the use of multiple interactions in the hierarchical organization of macromolecules to well-defined supramolecular assemblied were also examined.
725 citations
TL;DR: In this paper, the effect of adding nonlocal or gradient terms to the constitutive modeling may enhance the ability of the models to describe such situations, and the relation between these enhancements are examined in a continuum damage setting.
590 citations
TL;DR: In this article, the authors present tools to manipulate and minimize the band gap of conjugated (co)polymers, and the effects of minimization of the bond length alternation and incorporation of donor-π-acceptor units are discussed in particular.
Abstract: This paper reviews the tools to manipulate and minimize the band gap of conjugated (co)polymers. The effects of minimization of the bond length alternation and of the incorporation of donor-π-acceptor units are discussed in particular. A systematic study of a series of alternating donor–acceptor oligomers has revealed the achievable limits and allowed for a prognosis of the performance of corresponding copolymers. The decisive influence of the LUMO eigenvectors of the acceptors on the band gap is highlighted. A new synthesis of benzo[1,2-c:4,5-c]bis[1,2,5]thiadiazole containing donor–acceptor monomers and their acid-catalyzed polymerization are described. Finally, band gap tuning by appropriate substitution, conformational adjustment and mesoscopic ordering is discussed.
541 citations
TL;DR: In this paper, the authors report further evidence bearing on the relations among restorative experiences, self-regulation, and place attachment, and report that frequent mention of being relaxed, being away from everyday life, forgetting worries, and reflecting on personal matters indicated a link between favorite places and restorative experience.
Abstract: The authors report further evidence bearing on the relations among restorative experiences, self-regulation, and place attachment. University students (n = 101) described their favorite places and experiences in them, and 98 other students described unpleasant places. Natural settings were overrepresented among favorite places and underrepresented among the unpleasant places. In open-ended accounts, frequent mention of being relaxed, being away from everyday life, forgetting worries, and reflecting on personal matters indicated a link between favorite places and restorative experience. Restoration was particularly typical of natural favorite places. Structured evaluations of being away, fascination, coherence, and compatibility indicated they were experienced to a high degree in the favorite places, although fascination to a lesser degree than compatibility. The favorite and unpleasant places differed substantially in all four restorative qualities but especially in being away and compatibility. Self-refe...
520 citations
TL;DR: In this article, a methodology for analyzing the collective learning of the classroom community in terms of the evolution of classroom mathematical practices is described, and a sample analysis taken from a 1st-grade classroom teaching experiment is presented to illustrate how we coordinate a social perspective on communal practices with a psychological perspective on individual students' diverse ways of reasoning as they participate in those practices.
Abstract: In this article, we describe a methodology for analyzing the collective learning of the classroom community in terms of the evolution of classroom mathematical practices. To develop the rationale for this approach, we first ground the discussion in our work as mathematics educators who conduct classroom-based design research. We then present a sample analysis taken from a 1st-grade classroom teaching experiment that focused on linear measurement to illustrate how we coordinate a social perspective on communal practices with a psychological perspective on individual students’ diverse ways of reasoning as they participate in those practices. In the concluding sections of the article, we frame the sample analysis as a paradigm case in which to clarify aspects of the methodology and consider its usefulness for design research.
488 citations
TL;DR: A set of criteria is proposed that a good IO selection method should possess, which is used to assess and compare the methods and it could be used as a guideline for new methods.
442 citations
Book•
01 Jan 2001TL;DR: Wavelets and wavelet thresholding Smoothing non-equidistantly spaced data using second generation wavelets and thresholding and Bayesian correction with geometrical priors for image noise reduction.
Abstract: Wavelets and wavelet thresholding.- The minimum mean squared error threshold.- Estimating the minimum MSE threshold.- Thresholding and GCV applicability in more realistic situations.- Bayesian correction with geometrical priors for image noise reduction.- Smoothing non-equidistantly spaced data using second generation wavelets and thresholding.
TL;DR: In this article, transmission electron microscopy (TEM), dynamic oxygen chemisorption (DOC), and EXAFS were used to characterize supported MoS2 catalysts.
TL;DR: An overview of the literature on nonparametric or distribution-free control charts for univariate variables data is presented and connections to some areas of active research are made, such as sequential analysis, that are relevant to process control.
Abstract: The literature on nonparametric or distribution-free control charts for univariate variables data is examined. The advantages of these charts have over more traditional distribution-based control charts are demonstrated. Constructive criticism of the li..
TL;DR: In this paper, a summary of different elementary processes influencing the thermal balance and energetic conditions of substrate surfaces during plasma processing is given, and various contributions to the energy balance are given in a modular mathematical framework form and examples for an estimation of heat fluxes and numerical values of relevant coefficients for energy transfer, etc.
TL;DR: Recent developments in characterising Langmuir monolayers of a variety of film-forming materials and employing several physicochemical techniques are reviewed.
TL;DR: In this paper, the authors demonstrate that condensation polymerization of 2,5-bis(5-trimethylstannyl-2-thienyl)-N-dodecylpyrrole and 4,7-dibromo-2,1,3-benzothiadiazole in the presence of Pd(PPh3)2Cl2 as a catalyst affords a novel conjugated oligomeric material (PTPTB), which exhibits a low optical bandgap as a result of the alternation of electron-
Abstract: Low optical bandgap conjugated polymers may improve the efficiency of organic photovoltaic devices by increasing the absorption in the visible and near infrared region of the solar spectrum. Here we demonstrate that condensation polymerization of 2,5-bis(5-trimethylstannyl-2-thienyl)-N-dodecylpyrrole and 4,7-dibromo-2,1,3-benzothiadiazole in the presence of Pd(PPh3)2Cl2 as a catalyst affords a novel conjugated oligomeric material (PTPTB), which exhibits a low optical bandgap as a result of the alternation of electron-rich and electron-deficient units along the chain. By varying the molar ratio of the monomers in the reaction and fractionation of the reaction product, two different molecular weight fractions (PTPTB-I and PTPTB-II, see Experimental section) were isolated, containing 5–17 and 13–33 aromatic units respectively, as inferred from matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS). Thin films of PTPTB-I and PTPTB-II exhibit an optical bandgap of 1.60 and 1.46 eV, respectively. Photoinduced absorption (PIA) and photoluminescence spectroscopy of blends of PTPTB-I and a methanofullerene (1-(3-methoxycarbonyl)-propyl-1-phenyl-[6,6]C61, PCBM) gave direct spectral evidence of the photoinduced electron-transfer reaction from PTPTB-I as a donor to the fullerene derivative as an acceptor. Thin PTPTB-I:PCBM composite films were sandwiched between indium tin oxide/poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonic acid) (ITO/PEDOT:PSS) and Al electrodes to prepare working photovoltaic devices, which show an open circuit voltage of 0.67 V under white-light illumination. The spectral dependence of the device shows an onset of the photocurrent at 1.65 eV (750 nm).
TL;DR: In this paper, a new method for the computational analysis of fluid-structure interaction of a Newtonian fluid with slender bodies is developed, which combines ideas of the fictitious domain and the mortar element method by imposing continuity of the velocity field along an interface by means of Lagrange multipliers.
Abstract: A new method for the computational analysis of fluid-structure interaction of a Newtonian fluid with slender bodies is developed. It combines ideas of the fictitious domain and the mortar element method by imposing continuity of the velocity field along an interface by means of Lagrange multipliers. The key advantage of the method is that it circumvents the need for complicated mesh movement strategies common in arbitrary Lagrangian-Eulerian (ALE) methods, usually used for this purpose
TL;DR: In this paper, a flamelet-generated manifold method for premixed combustion systems is applied to laminar flames, which can be used to give accurate predictions, a semi-practical furnace is modeled and the results are compared with results of detailed computations.
TL;DR: In this paper, the authors studied the activity for ammonia oxidation and the intermediates formed during the reaction and found that the metal electrodissolution is enhanced by ammonia under these conditions.
04 Jun 2001
TL;DR: It is explained that the P2P approach yields an interorganizational workflow which is guaranteed to realize the behavior specified in the public workflow.
Abstract: This paper describes in an informal way the Public-To-Private (P2P) approach to interorganizational workflows, which is based on a notion of inheritance. The approach consists of three steps: (1) create a common understanding of the interorganizational workflow by specifying a shared public workflow, (2) partition the public workflow over the organizations involved, and (3) for each organization, create a private workflow which is a subclass of the respective part of the public workflow. Using an example, we explain that the P2P approach yields an interorganizational workflow which is guaranteed to realize the behavior specified in the public workflow.
TL;DR: In this paper, both monofunctional and bifunctional oligo(p-phenylene vinylene)s (OPVs) functionalized with ureido-s-triazine units have been synthesized and fully characterized.
Abstract: Mono- and bifunctional oligo(p-phenylene vinylene)s (OPVs) functionalized with ureido-s-triazine units have been synthesized and fully characterized. In chloroform monofunctional OPV derivatives dimerize with a dimerization constant of Kdim = (2.1 ± 0.3) × 104 L/mol, while bifunctional OPV derivatives are present as random coil polymers in this solvent. In more apolar solvents such as dodecane, the hydrogen-bonded dimers of the monofunctional OPV derivative aggregate in chiral stacks, as can be concluded from UV/vis, fluorescence and CD spectroscopy. Temperature-dependent measurements show a first-order transition at 53 ± 3 °C from the aggregated state to the molecularly dissolved phase. The bifunctional derivative also aggregates in dodecane; however, based on CD measurements, these aggregates are less organized. This behavior is presumably the outcome of a competition between favorable π−π interactions and restricted conformational freedom, due to the hexyl spacer, which results in a frustrated supramol...
TL;DR: Woflan as mentioned in this paper analyzes workflow process definitions downloaded from commercial workflow products using state-of-the-art Petri-net-based analysis techniques to locate the source of a design error.
Abstract: Workflow management technology promises a flexible solution for business-process support facilitating the easy creation of new business processes and modification of existing processes. Unfortunately, today’s workflow products have no support for workflow verification. Errors made at design-time are not detected and result in very costly failures at run-time. This paper presents the verification tool Woflan. Woflan analyzes workflow process definitions downloaded from commercial workflow products using state-of-the-art Petri-net-based analysis techniques. This paper describes the functionality of Woflan emphasizing diagnostics to locate the source of a design error. Woflan is evaluated via two case studies, one involving 20 groups of students designing a complex workflow process and one involving an industrial workflow process designed by Staffware Benelux. The results are encouraging and show that Woflan guides the user in finding and correcting errors in the design of workflows. Received 27 September 2000; revised 8 March 2001
TL;DR: This work set out to find an objective spectral measure for discontinuity, and studied the feasibility of extending the diphone database with context-sensitive diphones to reduce the occurrence of audible discontinuities.
Abstract: A common problem in diphone synthesis is discussed, viz., the occurrence of audible discontinuities at diphone boundaries. Informal observations show that spectral mismatch is the most likely the clause of this phenomenon. We first set out to find an objective spectral measure for discontinuity. To this end, several spectral distance measures are related to the results of a listening experiment. Then, we studied the feasibility of extending the diphone database with context-sensitive diphones to reduce the occurrence of audible discontinuities. The number of additional diphones is limited by clustering consonant contexts that have a similar effect on the surrounding vowels on the basis of the best performing distance measure. A listening experiment has shown that the addition of these context-sensitive diphones significantly reduces the amount of audible discontinuities.
TL;DR: A noisy yet positive effect of stereoscopic presentation on the lateral postural responses was demonstrated and a large effect of screen size on subjective presence ratings could be demonstrated, but only for the video stimulus that contained motion.
Abstract: Recently, we reported that group subjective measures of presence as well as observers' postural responses are sensitive to increasing the realism of a display with motion content, by the addition of stereoscopic information, using a 20-inch stereoscopic screen with an effective horizontal field of view of 28 deg. (Freeman, Avons, Meddis, Pearson, & IJsselsteijn, 2000). The experiment presented here employed a large projection display with a 50 deg. horizontal field of view showing a rally car traversing a curved track at speed. The independent variables included image motion and stereoscopic presentation as within-subjects factors and screen size as a between-subjects factor. Dependent variables included subjective measures of presence, vection, involvement, and sickness, as well as observers' lateral postural responses, which served as a candidate objective corroborative measure of presence. Results demonstrated a noisy yet positive effect of stereoscopic presentation on the lateral postural responses. Post-test subjective ratings revealed a significant effect of stereoscopic presentation on the subjective judgments of presence, but not on those of vection, involvement, or sickness. Image motion had a large and significant effect on the subjective judgments of presence, vection, and involvement. The effect of image motion was considerably larger than that of stereoscopic viewing. By comparing results between experiments, a large effect of screen size on subjective presence ratings could be demonstrated, but only for the video stimulus that contained motion. The postural response measure did not differentiate between screen sizes, thus limiting its utility as an objective corroborative measure of presence, although further research is required to be able to be more firm in our conclusion regarding this issue.
TL;DR: In this article, a molecular network is proposed to improve the stiffness/strength/toughness balance of polyamide-12 polysilicon composites by forming micro voids inside stacks of layered silicates.
TL;DR: The authors found that people who see greater potential for restorative experiences in natural environments also do more to protect them by behaving ecologically, as with recycling or reduced driving, and that fascination mediated the influences of coherence, being away, and compatibility.
Abstract: Shifting the focus from fear, guilt, and indignation related to deteriorating environmental quality, the authors hypothesized that people who see greater potential for restorative experiences in natural environments also do more to protect them by behaving ecologically, as with recycling or reduced driving. University students (N = 488) rated a familiar freshwater marsh in terms of being away, fascination, coherence, and compatibility, qualities of restorative person-environment transactions described in attention restoration theory. They also reported on their performance of various ecological behaviors. The authors tested a structural equation model with data from a randomly drawn subset of participants and then confirmed it with the data from a second subset. For the combined subsets, perceptions of the restorative qualities predicted 23% of the variance in general ecological behavior. As the only direct predictor, fascination mediated the influences of coherence, being away, and compatibility.
TL;DR: The helical structure of these isocyanopeptide polymers has the potential to be controlled through tailoring of the side branches and the hydrogen-bonding network present in the β-sheets.
Abstract: Polymerization of isocyanopeptides results in the formation of high molecular mass polymers that fold in a proteinlike fashion to give helical strands in which the peptide chains are arranged in beta-sheets. The beta-helical polymers retain their structure in water and unfold in a cooperative process at elevated temperatures. The peptide architecture in these polymers is a different form of the beta-helix motif found in proteins. Unlike their natural counterparts, which contain arrays of large beta-sheets stacked in a helical fashion, the isocyanopeptide polymers have a central helical core that acts as a director for the beta-sheet-like arrangement of the peptide side arms. The helical structure of these isocyanopeptide polymers has the potential to be controlled through tailoring of the side branches and the hydrogen-bonding network present in the beta-sheets.
TL;DR: In this paper, the influence of grain sizes on the processing of thin metal sheets was investigated in two different ways: first, by reduction of the sheet thickness at a constant grain size (investigated in tension), and secondly, by changing the grain size at constant sheet thickness, and the results showed that in both the experiments, the yield strength as well as the maximum load decrease with a decreasing number of grains over the thickness.
TL;DR: Results suggest that basic needs and motives, such as thirst, causes a heightened perceptual readiness to environmental cues that are instrumental in satisfying these needs.
Abstract: The present research is concerned with cognitive effects of habitually regulated primary motives. Specifically, two experiments tested the idea that feelings of thirst enhance the cognitive accessibility of, or readiness to perceive, action-relevant stimuli. In a task allegedly designed to assess mouth-detection skills, some participants were made to feel thirsty, whereas others were not. Results showed that participants who were made thirsty responded faster to drinking-related items in a lexical decision task, and performed better on an incidental recall task of drinking-related items, relative to no-thirst control participants. These results suggest that basic needs and motives, such as thirst, causes a heightened perceptual readiness to environmental cues that are instrumental in satisfying these needs.