Showing papers by "Eindhoven University of Technology published in 1998"

The application of Petri-nets to workflow management

Abstract: Workflow management promises a new solution to an age-old problem: controlling, monitoring, optimizing and supporting business processes. What is new about workflow management is the explicit representation of the business process logic which allows for computerized support. This paper discusses the use of Petri nets in the context of workflow management. Petri nets are an established tool for modeling and analyzing processes. On the one hand, Petri nets can be used as a design language for the specification of complex workflows. On the other hand, Petri net theory provides for powerful analysis techniques which can be used to verify the correctness of workflow procedures. This paper introduces workflow management as an application domain for Petri nets, presents state-of-the-art results with respect to the verification of workflows, and highlights some Petri-net-based workflow tools.

Predicting behavior from actions in the past : repeated decision making or a matter of habit?

Abstract: This paper summarizes research on determinants of repeated behaviors, and the decision processes underlying them. The present research focuses on travel mode choices as an example of such behaviors. It is proposed that when behavior is performed repeatedly and becomes habitual, it is guided by automated cognitive processes, rather than being preceded by elaborate decision processes (i.e., a decision based on attitudes and intentions). First, current attitude-behavior models are discussed, and the role of habit in these models is examined. Second, research is presented on the decision processes preceding travel mode choices. Based on the present theoretical and empirical overview, it is concluded that frequently performed behavior is often a matter of habit, thereby establishing a boundary condition for the applicability of attitude-behavior models. However, more systematic research is required to disentangle the role of habit in attitude-behavior models and to learn more about the cognitive processes underlying habitual behavior.

Efficient collision detection of complex deformable models using AABB trees

Abstract: We present a scheme for exact collision detection between complex models undergoing rigid motion and deformation. The scheme relies on a hierarchical model representation using axis-aligned bounding boxes (AABBs). Recent work has shown that AABB trees are slower than oriented bounding box (OBB) trees for performing overlap tests. In this paper, we describe a way to speed up overlap tests between AABBs, such that for collision detection of rigid models, the difference in performance between the two representations is greatly reduced. Furthermore, we show how to update an AABB tree quickly as a model is deformed. We thus find AABB trees to be the method of choice for collision detection of complex models undergoing deformation. In fact, because they are not much slower to test, are faster to build, and use less storage than OBB trees, AABB trees might be a reasonable choice for rigid models as well.

Strong dimerization of ureidopyrimidones via quadruple hydrogen bonding

Abstract: 6-Methyl-2-butylureidopyrimidone dimerizes via four hydrogen bonds in the solid state as well as in CHCl3 solution via a donor−donor−acceptor−acceptor (DDAA) array of hydrogen bonding sites in the 4[1H]-pyrimidinone tautomer. An intramolecular hydrogen bond from the pyrimidine NH group to the urea oxygen atom preorganizes the molecules for dimerization. The dimerization constant of the dimer in CHCl3 exceeds 106 M-1. In CHCl3 containing DMSO, the dimer is in equilibrium with the monomeric 6[1H]-pyrimidinone tautomer. In 6-phenyl-2-butylureidopyrimidone, the 4[1H]-pyrimidinone tautomer coexists with the pyrimidin-4-ol form, which dimerizes with similar high dimerization constants via four hydrogen bonds in a DADA array. The latter tautomer predominates in derivatives with electronegative 6-substituents, like 6-nitrophenyl- and 6-trifluoromethyl-2-butylureidopyrimidone. Due to its simple preparation and high dimerization constant, the ureidopyrimidone functionality is a useful building block for supramolecu...

Habit versus planned behaviour: A field experiment

Abstract: A field experiment investigated the prediction and change in repeated behaviour in the domain of travel mode choices. Car use during seven days was predicted from habit strength (measured by self-reported frequency of past behaviour, as well as by a more covert measure based on personal scripts incorporating the behaviour), and antecedents of behaviour as conceptualized in the theory of planned behaviour (attitude, subjective norm, perceived behavioural control and behavioural intention). Both habit measures predicted behaviour in addition to intention and perceived control. Significant habit x intention interactions indicated that intentions were only significantly related to behaviour when habit was weak, whereas no intention-behaviour relation existed when habit was strong. During the seven-day registration of behaviour, half of the respondents were asked to think about the circumstances under which the behaviour was executed. Compared to control participants, the behaviour of experimental participants was more strongly related to their previously expressed intentions. However, the habit-behaviour relation was unaffected. The results demonstrate that, although external incentives may increase the enactment of intentions, habits set boundary conditions for the applicability of the theory of planned behaviour.

Observation of a Feshbach Resonance in Cold Atom Scattering

Abstract: We probe $s$-wave collisions of laser-cooled ${}^{85}\mathrm{Rb}({f\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}2,m}_{f}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\ensuremath{-}2)$ atoms with Zeeman-resolved photoassociation spectroscopy. We observe that these collisions exhibit a magnetically tunable Feshbach resonance, and determine that this resonance tunes to zero energy at a magnetic field of $164\ifmmode\pm\else\textpm\fi{}7\mathrm{G}$. This result indicates that the self-interaction energy of an ${}^{85}\mathrm{Rb}$ Bose-Einstein condensate can be magnetically tuned. We also demonstrate that Zeeman-resolved photoassociation spectroscopy provides a useful new tool for the study of ultracold atomic collisions.

AHA! An open Adaptive Hypermedia Architecture

Abstract: Hypermedia applications generate comprehension and orientation problems due to their rich link structure. Adaptive hypermedia tries to alleviate these problems by ensuring that the links that are offered and the content of the information pages are adapted to each individual user. This is done by maintaining a user model. Most adaptive hypermedia systems are aimed at one specific application. They provide an engine for maintaining the user model and for adapting content and link structure. They use a fixed screen layout that may include windows (HTML frames) for an annotated table of contents, an overview of known or missing knowledge, etc. Such systems are typically closed and difficult to reuse for very different applications. We present AHA, an open Adaptive Hypermedia Architecture that is suitable for many different applications. This paper concentrates on the adaptive hypermedia engine, which maintains the user model and which filters content pages and link structures accordingly. The engine...

Scheduling a batching machine

Abstract: We address the problem of scheduling n jobs on a batching machine to minimize regular scheduling criteria that are non-decreasing in the job completion times A batching machine is a machine that can handle up to b jobs simultaneously The jobs that are processed together form a batch, and all jobs in a batch start and complete at the same time The processing time of a batch is equal to the largest processing time of any job in the batch We analyse two variants: the unbounded model, where b⩾n; and the bounded model, where b1; for the case with m different processing times, we give a dynamic programming algorithm that requires O(b2m22m) time Moreover, we prove that due date based scheduling criteria give rise to NP-hard problems Finally, we show that an arbitrary regular cost function can be minimized in polynomial time for a fixed number of batches © 1998 John Wiley & Sons, Ltd

Stick-slip vibrations induced by alternate friction models

Abstract: In the present paper a simple and efficient alternate friction model is presented to simulate stick-slip vibrations. The alternate friction model consists of a set of ordinary non-stiff differential equations and has the advantage that the system can be integrated with any standard ODE-solver. Comparison with a smoothing method reveals that the alternate friction model is more efficient from a computational point of view. A shooting method for calculating limit cycles, based on the alternate friction model, is presented. Time-dependent static friction is studied as well as application in a system with 2-DOF.

Mixed finite element methods for viscoelastic flow analysis : a review

Abstract: The progress made during the past decade in the application of mixed finite element methods to solve viscoelastic flow problems using differential constitutive equations is reviewed. The algorithmic developments are discussed in detail. Starting with the classical mixed formulation, the elastic viscous stress splitting (EVSS) method as well as the related discrete EVSS and the so-called EVSS-G method are discussed among others. Furthermore, stabilization techniques such as the streamline upwind Petrov‐Galerkin (SUPG) and the discontinuous Galerkin (DG) are reviewed. The performance of the numerical schemes for both smooth and non-smooth benchmark problems is discussed. Finally, the capabilities of viscoelastic flow solvers to predict experimental observations are reviewed. # 1998 Elsevier Science B.V. All rights reserved.

Self-Complementarity Achieved through Quadruple Hydrogen Bonding

Abstract: Highly stable dimers are formed in solution and in the solid state by a class of readily synthesized, self-complementary building blocks for supramolecular chemistry, which associate through a donor-acceptor-donor-acceptor array of four hydrogen-bonding sites. An additional intramolecular hydrogen bond in the compound whose crystal structure is shown on the right preorganizes the molecule for dimerization.

Amphiphilic dendrimers as building blocks in supramolecular assemblies

Abstract: The self-assembly of amphiphilic dendrimers based on poly(propylene imine) dendrimers of five different generations with up to 64 end groups modified with long hydrophobic chains has been studied. At the air−water interface stable monolayers form in which the dendritic surfactants presumably adopt a cylindrical shape; all the chains are aligned perpendicular to the water surface, and the dendritic poly(propylene imine) core faces the aqueous phase. Electron microscopy and dynamic light-scattering measurements performed on aqueous solutions of the amphiphiles at pH = 1 showed the formation of small spherical aggregates with diameters varying between 20 and 200 nm. X-ray diffraction of cast films of these aggregates revealed bilayer thicknesses of 48−54 A. A phase transition was detected by measuring fluorescence anisotropy. The theoretical volumes of the dendritic amphiphiles were in good agreement with those calculated from the monolayer experiments and X-ray diffraction data. Hence, the amphiphilic dendr...

An asynchronous low-power 80C51 microcontroller

Abstract: This paper presents a low-power asynchronous implementation of the 80C51 microcontroller. It was realized in a 0.5 /spl mu/ CMOS process and it shows a power advantage of a factor 4 compared to a recent synchronous implementation in the same technology. The chip is fully bit compatible with the synchronous implementation, and timing compatible for external memory access. The circuit is a compiled VLSI-program, using Tangram as VLSI-programming language and the Tangram tool-set to compile the design automatically to a standard-cell netlist. This design approach proves to be powerful enough to describe the microcontroller and derive an efficient implementation. Further, it offers the designer the possibility to explore various alternatives in the design space.

Redox States of Long Oligothiophenes: Two Polarons on a Single Chain

Abstract: Can two isolated radical cations (polarons) exist simultaneously on a π-conjugated chain or do they coalesce into a single, doubly charged spinless (bipolaron) deformation? This long-standing question, fundamental to charge transport in conducting polymers, is now resolved by an investigation of the redox states of long oligothiophenes (below) in solution. In contrast to short oligothiophenes, for long oligothiophene dications two individual polarons prevail because of the decrease in Coulomb repulsion energy obtained by moving the two charges apart.

Efficient Monte Carlo methods for the simulation of catalytic surface reactions

Abstract: Monte Carlo methods for the simulation of the dynamic behavior of surface reactions are developed, based on the chemical master equation. The methods are stated in a general framework which makes them applicable to a variety of models. Three methods are developed. A comparative analysis of the performance of the three methods, both theoretically and empirically, is included.

Investigating consumers" tendency to combine multiple shopping purposes and destinations

Abstract: Because of the increasing time pressure they face, many consumers are becoming more concerned about the efficiency of their shopping patterns. Retailers have recognized this trend and have improved shopping convenience by offering greater variety in product categories and making it easier for consumers to combine visits to multiple stores. However, little is known about how consumers improve the efficiency of their shopping trips or how changes in retail supply affect the way in which consumers combine multiple purposes and destinations. Building on previous work in consumer shopping trip modeling and conjoint design theory, the authors introduce a choice-based conjoint approach to studying and modeling this phenomenon. The authors illustrate the approach in a case study that investigates the tendency of Dutch shoppers to combine grocery, drugstore, and clothing purchases across multiple shopping destinations. The authors observe that the tendency of consumers to combine purchases differs from category to category and depends on category availability. In general, consumers combine considerably fewer purchases than could be expected if their shopping trip planning was based purely on travel cost minimization.

Do networks matter for innovation? The usefulness of the network approach in analysing innovation

Abstract: Economic network theory emphasises the importance of external resource mobilisation. In this paper, the relations between the mobilisation and use of internal and external resources in innovation processes, and the innovative performance of firms, are explored empirically, using an adapted version of Hakansson's (1987) economic network model. The main research question was: to what extent do network variables contribute to the innovative performance of firms? To answer this question, we assessed the explanatory power of economic network theory within the empirical study of innovation. Firms were found to engage in various configurations of internal and external resource bases, enabling them to innovate with better results. The relations in the estimated models are strongly influenced by moderating variables such as sector, and type and level of innovations produced. Our main conclusion is that models that include both internal and external resources explain the innovative performance better than models in which only internal resources are used.

The context-tree weighting method: extensions

Abstract: First we modify the basic (binary) context-tree weighting method such that the past symbols x/sub 1-D/, x/sub 2-D/, ..., x/sub 0/ are not needed by the encoder and the decoder. Then we describe how to make the context-tree depth D infinite, which results in optimal redundancy behavior for all tree sources, while the number of records in the context tree is not larger than 2T-1. Here T is the length of the source sequence. For this extended context-tree weighting algorithm we show that with probability one the compression ratio is not larger than the source entropy for source sequence length T/spl rarr//spl infin/ for stationary and ergodic sources.

Autonomous Norm Acceptance

Abstract: It is generally acknowledged that norms and normative action emphasize autonomy on the side of decision. But what about the autonomous formation of normative goals? This paper is intended to contribute to a theory of how agents form normative beliefs and goals, and to formulate general but non exhaustive principles of norm based autonomous agent-hood - namely goal generation and decision making- upon which to construct software agents.

A constitutive equation for the elasto-viscoplastic deformation of glassy polymers

Abstract: Constitutive equations for finite elastic-plastic deformation of polymers and metals are usually formulated by assuming an isotropic relation between the Jaumann rate of the Cauchy-stress tensor and the strain-rate tensor. However, the Jaumann-stress rate is known to display spurious non- physical behaviour in the elastic region. Replacing the Jaumann-stress rate by a Truesdell-stress rate results in an adequate description in the elastic region, but gives rise to a volume decrease during plastic flow in tensile deformation. In this paper a "compressible-Leonov model" is introduced, in which the elastic volume response is rigorously separated from the elasto-viscoplastic isochoric de- formation. This has the advantage that the model can be extended in a straightforward way to include a spectrum of relaxation times. It is shown that in the limit of small elastic strains, the compressible Leonov model reduces to the Jaumann-stress rate model, but diverges from the Truesdell-stress rate model. Finally, a comparison is made of the above mentioned models in a homogeneous uniaxial ten- sile test and a homogeneous plane-stress shear test, using polycarbonate (PC) as a model system. All models considered in this paper are "single mode" models (i.e. one relaxation time), and, therefore, cannot describe the full (non)linear viscoelastic region, nor the strain-hardening or strain-softening response.

Band‐Gap Engineering of Donor–Acceptor‐Substituted π‐Conjugated Polymers

Abstract: Some practical guidelines for the design of novel low-band-gap systems. Various donor–acceptor π-conjugated oligomers with different chain lengths containing electron-donating thiophene or pyrrole rings and electron-withdrawing 2,1,3-benzothiadiazole (like the one shown here) or quinoxaline rings have been synthesized by Stille cross-coupling. The UV/Vis absorption behavior of these systems is used to give guidelines for donor–acceptor based low-band-gap or even intrinsically conducting polymers.

Rankings of Graphs

Abstract: A vertex (edge) coloring $\phi:V\rightarrow \{1,2,\ldots ,t\}$ ($\phi':E\rightarrow \{1,2,\ldots,$ $t\}$) of a graph G=(V,E) is a vertex (edge) t-ranking if, for any two vertices (edges) of the same color, every path between them contains a vertex (edge) of larger color. The {\em vertex ranking number} $\chi_{r}(G)$ ({\em edge ranking number} $\chi_{r}'(G)$) is the smallest value of t such that G has a vertex (edge) t-ranking. In this paper we study the algorithmic complexity of the {\sc Vertex Ranking} and {\sc Edge Ranking} problems. It is shown that $\chi_{r}(G)$ can be computed in polynomial time when restricted to graphs with treewidth at most k for any fixed k. We characterize the graphs where the vertex ranking number $\chi_{r}$ and the chromatic number $\chi$ coincide on all induced subgraphs, show that $\chi_{r}(G)=\chi (G)$ implies $\chi (G)=\omega (G)$ (largest clique size), and give a formula for $\chi_{r}'(K_n)$.