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Showing papers by "Eindhoven University of Technology published in 1999"


Journal ArticleDOI
14 Oct 1999-Nature
TL;DR: In this article, the authors used thin-film, field effect transistor structures to probe the transport properties of the ordered microcrystalline domains in the conjugated polymer poly(3-hexylthiophene), P3HT.
Abstract: Self-organization in many solution-processed, semiconducting conjugated polymers results in complex microstructures, in which ordered microcrystalline domains are embedded in an amorphous matrix1. This has important consequences for electrical properties of these materials: charge transport is usually limited by the most difficult hopping processes and is therefore dominated by the disordered matrix, resulting in low charge-carrier mobilities2 (⩽10-5 cm2 V-1 s-1). Here we use thin-film, field-effect transistor structures to probe the transport properties of the ordered microcrystalline domains in the conjugated polymer poly(3-hexylthiophene), P3HT. Self-organization in P3HT results in a lamella structure with two-dimensional conjugated sheets formed by interchain stacking. We find that, depending on processing conditions, the lamellae can adopt two different orientations—parallel and normal to the substrate—the mobilities of which differ by more than a factor of 100, and can reach values as high as 0.1 cm2 V-1 s-1 (refs 3, 4). Optical spectroscopy of the field-induced charge, combined with the mobility anisotropy, reveals the two-dimensional interchain character of the polaronic charge carriers, which exhibit lower relaxation energies than the corresponding radical cations on isolated one-dimensional chains. The possibility of achieving high mobilities via two-dimensional transport in self-organized conjugated lamellae is important for applications of polymer transistors in logic circuits5 and active-matrix displays4,6.

4,306 citations



Journal ArticleDOI
TL;DR: The theory and practice of a novel approach for sample enrichment, namely the application of stir bars coated with the sorbent polydimethylsiloxane (PDMS) and referred to as stir bar sorptive extraction (SBSE) are presented in this paper.
Abstract: The theory and practice of a novel approach for sample enrichment, namely the application of stir bars coated with the sorbent polydimethylsiloxane (PDMS) and referred to as stir bar sorptive extraction (SBSE) are presented. Stir bars with a length of 10 and 40 mm coated with 55 and 219 μL of PDMS liquid phase, respectively were applied. The 10-mm stir bars are best suited for stirring sample volumes from 10 up to 50 mL whereas 40-mm stir bars are more ideal for sample volumes up to 250 mL. Depending on sample volume and the stirring speed, typical stirring times for equilibration are between 30 and 60 min. The performance of SBSE is illustrated with the analysis of volatile and semivolatile micropollutants from aqueous samples. Detection limits using mass selective detection are in the low ng/L range for a wide selection of analytes from the EPA priority pollutant lists including analytes ranging in volatility from 1,1,1-trichloroethane to chrysene. For the extraction of selected compounds from 200-mL samples, detection limits below 0.1 ng/L are reached in the selected ion monitoring mode. A comparison between SBSE and solid-phase microextraction is made. ©1999 John Wiley & Sons, Inc. J Micro Sep 11: 737–747, 1999

1,362 citations


Journal ArticleDOI
TL;DR: In this article, the authors argue that a habit seems to be accompanied by an enduring cognitive orientation, which they refer to as "habitual mind-set" that makes an individual less attentive to new information and courses of action, and thus contributes to the maintenance of habits.
Abstract: Habit is often treated as a construct of marginal interest in the literature on attitude–behaviour relations. We argue that this is undeserved, particularly given the current interest in principles of automaticity in social psychology. Basic features of habits, such as goal-directed automaticity, their dependency on situational constancy, and functionality, as well as the measurement of habit strength, are discussed. Research is reviewed that contrasted habit with deliberate action, as approached from the theory of planned behaviour, spontaneous vs. deliberate attitude–behaviour processes, implementation intention theory, and decision-making models. Habits thus appear as boundary conditions of the validity of models of planned behaviour and rational decision-making. A habit seems to be accompanied by an enduring cognitive orientation, which we refer to as “habitual mind-set”, that makes an individual less attentive to new information and courses of action, and thus contributes to the maintenance of habitu...

950 citations


Journal ArticleDOI
TL;DR: In this paper, the authors present an approach to give formal semantics to Event-driven Process Chains (EPCs) by mapping EPCs (without connectors of type ∨) onto Petri nets.
Abstract: For many companies, business processes have become the focal point of attention. As a result, many tools have been developed for business process engineering and the actual deployment of business processes. Typical examples of these tools are Business Process Reengineering (BPR) tools, Enterprise Resource Planning (ERP) systems, and Workflow Management (WFM) systems. Some of the leading products, e.g. SAP R/3 (ERP/WFM) and ARIS (BPR), use Event-driven Process Chains (EPCs) to model business processes. Although the EPCs have become a widespread process modeling technique, they suffer from a serious drawback: neither the syntax nor the semantics of an EPC are well defined. In this paper, this problem is tackled by mapping EPCs (without connectors of type ∨) onto Petri nets. The Petri nets have formal semantics and provide an abundance of analysis techniques. As a result, the approach presented in this paper gives formal semantics to EPCs. Moreover, many analysis techniques are available for EPCs. To illustrate the approach, it is shown that the correctness of an EPC can be checked in polynomial time by using Petri-net-based analysis techniques.

693 citations


Journal ArticleDOI
TL;DR: In the computations, the shear thinning behavior of the analog blood fluid was incorporated through the Carreau-Yasuda model, and this seems to be the dominant non-Newtonian property of the blood analog fluid under steady flow conditions.

517 citations


Proceedings ArticleDOI
01 Feb 1999
TL;DR: A reference model for adaptive hypermedia applications, called AHAM, is described, which encompasses most features supported by adaptive systems that exist today or that are being developed (and have been published about).
Abstract: Hypermedia applications offer users the impression that there are many meaningful ways to navigate through a large body of information nodes. This rich link structure not only creates orientation problems, it may also be a source of comprehension problems when users follow paths through the information which the author did not foresee. Adaptive techniques have been used by a number of researchers [1, 2, 4, 5, 6, 7, 8, 9, 10, 17, 19, 20, 22] in an attempt to offer guidance through and orientation support for rich link structures. The majority of these adaptive hypermedia systems (AHS) have been used in educational applications. The terminology used in this paper also has an educational “flavor”. However, there are some adaptive on-line information systems (or “kiosk”systems), adaptive information retrieval systems, and other adaptive hypermedia applications. In this paper we describe a reference model for adaptive hypermedia applications, called AHAM, which encompasses most features supported by adaptive systems that exist today or that are being developed (and have been published about). Our description of AHS is based on the Dexter model [15, 16], a widely used reference model for hypermedia. The description is kept somewhat informal in order to be able to explain AHAM rather than formally specify it. AHAM augments Dexter with features for doing adaptation based on a user model which persists beyond the duration of a session. Key aspects in AHAM are: Paul De Bra is also affiliated with the University of Antwerp, Belgium, and with the “Centrum voor Wiskunde en Informatica” (CWI) in Amsterdam. yGeert-Jan Houben is also affiliated with the University of Antwerp, Belgium, and with Origin in Eindhoven. The adaptation is based on a domain model, a user model and a teaching model which consists of pedagogical rules. We give a formal definition of each of these (sub)models (but only describe the pedagogical rules informally throughexamples). We distinguish the notions of concept, page and fragment. In some AHS these notions are confused. We provide a formalism which lets authors write pedagogical rules (about concepts) in such a way that they can be applied automatically. We illustrate various aspects of AHAM by means of some features of some well-known AHS [6, 10].

494 citations


Proceedings ArticleDOI
24 Oct 1999
TL;DR: A new method is presented to get an insight into univariate time series data to cluster similar daily data patterns, and to visualize the average patterns as graphs and the corresponding days on a calendar.
Abstract: A new method is presented to get an insight into univariate time series data. The problem addressed is how to identify patterns and trends on multiple time scales (days, weeks, seasons) simultaneously. The solution presented is to cluster similar daily data patterns, and to visualize the average patterns as graphs and the corresponding days on a calendar. This presentation provides a quick insight into both standard and exceptional patterns. Furthermore, it is well suited to interactive exploration. Two applications, numbers of employees present and energy consumption, are presented.

447 citations



Journal ArticleDOI
TL;DR: In this article, the authors describe the results of a study on strategies of third-party logistics (TPL) providers and present empirical findings for a strategic segmentation of the industry.
Abstract: In this article, the authors describe the results of a study on strategies of third‐party logistics (TPL) providers. The size of the TPL industry and the different requirements placed on logistics as opposed to basic services, such as transportation or public warehousing, justify the need to treat TPL as a separate industry. The authors describe three waves of entrants into the TPL industry and a taxonomy for value creation by logistics providers. Empirical findings for a strategic segmentation of the industry are presented. The strategic segmentation is connected to the waves of entrants and the taxonomy by an evaluation of required skills of TPL players. The TPL industry will soon reach an initial stage of maturity, but further changes are to be expected.

363 citations


Journal ArticleDOI
TL;DR: In this paper, a numerical and experimental investigation of unsteady entry flow in a 90 degrees curved tube is presented to study the impact of the non-Newtonian properties of blood on the velocity distribution.

Journal ArticleDOI
TL;DR: A framework for adaptive hypermedia systems (AHS) is introduced and some popular methods and techniques for adaptation are described, to illustrate the potential benefits of using adaptation in hypermedia applications.
Abstract: The navigational freedom in conventional hypermedia applications leads to comprehension and orientation problems (Nielsen 1990). Adaptive hypermedia attempts to overcome these problems by adapting the presentation of information and the overall link structure, based on a user model. This paper introduces a framework for adaptive hypermedia systems (AHS). It briefly describes some popular methods and techniques for adaptation. Examples and evaluations of existing AHS are used to illustrate the potential benefits of using adaptation in hypermedia applications.

Journal ArticleDOI
TL;DR: In this paper, the synthesis and optical properties of the disubstituted derivative PProDOT-Me2 are compared and compared with those of pProDot-Me and PPro-DOT.
Abstract: Dark opaque blue to transmissive light blue is the color transition that poly(3,4-propylenedioxythiophene) (PProDOT) and derivatives undergo when switched from their reduced to oxidized state. These polymers are very promising electrochromic materials - they exhibit more rapid switching, lower oxidation potentials, and greater stability than polythiophene. The synthesis and optical properties of the disubstituted derivative PProDOT-Me2 are reported and compared with those of PProDOT-Me and PProDOT. Substitution is found to improve the polymers electrochromic properties.

Journal ArticleDOI
TL;DR: In this paper, an exploratory causal model of goals, barriers, and enablers on the road towards effective international supply chain management (ISCM) is presented, and the results point at a disturbingly gloomy picture of vicious cycles frustrating the implementation of effective ISCM strategies.
Abstract: An increasing number of companies claim to pursue international supply chain management (ISCM), but the empirical evidence of successful implementation programs is still scarce. This paper aims to contribute to theory‐building in this area by presenting an exploratory causal model of goals, barriers, and enablers on the road towards effective ISCM. The model was established in a workshop with a panel of content matter experts. The results point at a disturbingly gloomy picture of vicious cycles frustrating the implementation of effective ISCM strategies. Fortunately, it appears that it is possible to apply the same generic mechanisms to create a virtuous cycle, for instance by promoting cross‐functional careers and by actively responding to demanding customer needs. The challenge ahead is to test the model’s content and validity.

Book ChapterDOI
15 Aug 1999
TL;DR: A publicly verifiable secret sharing (PVSS) scheme is a veri fiable secret sharing scheme with the property that the validity of the shares distributed by the dealer can be verified by any party; hence verification is not limited to the respective participants receiving the shares as discussed by the authors.
Abstract: A publicly verifiable secret sharing (PVSS) scheme is a veri fiable secret sharing scheme with the property that the validity of the shares distributed by the dealer can be verified by any party; hence verification is not limited to the respective participants receiving the shares. We present a new construction for PVSS schemes, which compared to previous solutions by Stadler and later by Fujisaki and Okamoto, achieves improvements both in efficiency and in the type of intractability assumptions. The running time is O(nk), where k is a security parameter, and n is the number of participants, hence essentially optimal. The intractability assumptions are the standard Diffie-Hellman assumption and its decisional variant. We present several applications of our PVSS scheme, among which is a new type of universally verifiable election scheme based on PVSS. The election scheme becomes quite practical and combines several advantages of related electronic voting schemes, which makes it of interest in its own right.

Journal ArticleDOI
TL;DR: In this paper, a review is given on transport and equilibrium sorption of moisture in polymer films and organic coatings, assimilating the impact of pigments, fillers and additives.

Proceedings ArticleDOI
24 Oct 1999
TL;DR: A new method is presented for the visualization of hierarchical information, such as directory structures and organization structures, based on recursive subdivision of a rectangular image space, which consists of recursive cushions.
Abstract: A new method is presented for the visualization of hierarchical information, such as directory structures and organization structures. Cushion treemaps inherit the elegance of standard treemaps: compact, space-filling displays of hierarchical information, based on recursive subdivision of a rectangular image space. Intuitive shading is used to provide insight in the hierarchical structure. During the subdivision, ridges are added per rectangle, which are rendered with a simple shading model. The result is a surface that consists of recursive cushions. The method is efficient, effective, easy to use and implement, and has a wide applicability.

Journal ArticleDOI
TL;DR: This paper presents some concepts and their relations that are necessary for modeling autonomous agents in an environment that is governed by some social norms and shows how deontic logic and the theory of speech acts can be used to model the generation of (some of) the norms.
Abstract: In this paper we present some concepts and their relations that are necessary for modeling autonomous agents in an environment that is governed by some (social) norms. We divide the norms over three levels: the private level the contract level and the convention level. We show how deontic logic can be used to model the concepts and how the theory of speech acts can be used to model the generation of (some of) the norms. Finally we give some idea about an agent architecture incorporating the social norms based on a BDI framework.

Journal ArticleDOI
TL;DR: The ureido-pyrimidone network as mentioned in this paper is the first example of a truly reversible polymer network showing these features, and it can be used to construct supramolecular materials possessing acceptable mechanical properties.
Abstract: The strong dimerizing, quadruple hydrogen-bonding ureido-pyrimidone unit is used to obtain reversible polymer networks. A new synthetic route from commercially available starting materials is described. The hydrogen-bonding ureido-pyrimidone network is prepared using 3(4)-isocyanatomethyl-1-methylcyclohexyl-isocyanate (IMCI) in the regioselective coupling reaction of multi-hydroxy functionalized polymers with isocytosines. 1H- and 13C-NMR, IR, MS, and ES-MS analysis, performed on a model reaction using butanol, demonstrated the formation of the hydrogen-bonding ureido-pyrimidone unit in a yield of more than 95%. The well-defined, strong hydrogen-bonding ureido-pyrimidone network is compared with a traditional covalently bonded polymer network, a multi-directional hydrogen-bonded polymer network based on urea units, and a reference compound. The advantage of the reversible, hydrogen-bonded polymer networks is the formation of the thermodynamically most favorable products, which show a higher “virtual” molecular weight and shear modulus, compared to the irreversible, covalently bonded polymer network. The properties of the ureido-pyrimidone network are unique; the well-defined and strong dimerization of the ureido-pyrimidone unit does not require any additional stabilization such as crystallization or other kinds of phase separation, and displays a well-defined viscoelastic transition. The ureido-pyrimidone network represents the first example of a truly reversible polymer network showing these features. Furthermore, the ureido-pyrimidone dimerization is strong enough to construct supramolecular materials possessing acceptable mechanical properties. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3657–3670, 1999

Journal Article
TL;DR: This paper uses message sequence charts to specify the interaction between organizations and Petri nets are used to model the workflows inside each organization.
Abstract: To date, workflow management focuses on improving the effectivity and efficiency of business processes within one organization. However, today’s corporations are challenged to cross organizational boundaries. Phenomena such as electronic commerce, extended enterprises and the Internet stimulate the cooperation between organizations. Therefore, it is interesting to consider workflows distributed over a number of organizations. Interorganizational workflow offers companies the opportunity to re-shape business processes beyond the boundaries of individual organizations. In this paper, we use message sequence charts to specify the interaction between organizations. Petri nets are used to model the workflows inside each organization. Two challenging problems related to interorganizational workflow are tackled in this paper: (1) What are the minimal requirements any interorganizational workflow should satisfy?, and (2) How to decide whether an interorganizational workflow (modeled in terms of Petri nets) is consistent with the interaction structure specified in terms of a message sequence chart?

Journal ArticleDOI
TL;DR: An implementation of the Gilbert-Johnson-Keerthi algorithm for comput ing the distance between convex objects, that has improved performance, robustness, and versatility over earlier implementations is presented.
Abstract: This paper presents an implementation of the Gilbert-Johnson-Keerthi algorithm for comput ing the distance between convex objects, that has improved performance, robustness, and versatility over earlier implementations. The algorithm presented here is especially suitable for use in collision detection of objects modeled using various types of geometric primitives, such as boxes, cones, and spheres, and their images under affine transformation.

Journal ArticleDOI
TL;DR: A normative framework for multilevel design of diagnostic controls, i.e., performance measurement systems, is proposed, an attempt to synthesise a design theory from systems theory and cybernetics, using a composite of the goal-oriented model, the multiple-constituency model and the natural-systems model of organisation.

Journal ArticleDOI
TL;DR: In this article, M/ZSM-5 zeolites with M = Ga, Fe, or Zn were prepared by subliming volatile compounds onto HZSM, and they were characterized by XRD, H2-TPR, CO TPR, FTIR, adsorption of pyridine and acetonitrile-d3, also by ESR spectroscopy.
Abstract: M/ZSM-5 zeolites with M = Ga, Fe, or Zn were prepared by subliming volatile compounds onto HZSM-5. They were characterized by XRD, H2-TPR, CO-TPR, FTIR, adsorption of pyridine and acetonitrile-d3 and, in the case of Fe/ZSM-5, also by ESR spectroscopy. Immediately after sublimation, the concentration of Bronsted acid sites is low, but with Ga/ZSM-5 and Fe/ZSM-5, it rises again after hydrolysis. This dissipation of multipositive ions to monopositive ions, each located near the negative countercharge in the zeolite matrix, is favored by a considerable gain in Coulomb energy. In Ga/ZSM-5, some of the regenerated Bronsted sites are stronger than those in the original HZSM-5. In Fe/ZSM-5 and Zn/ZSM-5, such Bronsted sites are weaker, as evidenced by CD3CN adsorption. However strong Lewis acid sites are formed, they are characterized by NH3-TPD, and pyridine and CD3CN adsorption. Zeolites with a high Si/Al ratio contain lattice defects with internal silanol groups. These defects disappear when metal ions are adde...

Journal ArticleDOI
TL;DR: In this paper, the authors argue that rapid economic and technological developments have overthrown traditional thinking about alliances and that firms could benefit from a new perspective on partnering, referred to as High Touch Partnering.
Abstract: Despite the trend towards an increasing use of strategic technology alliances, mortality rates of cooperative agreements have always been extremely high. In this paper we argue that rapid economic and technological developments have overthrown traditional thinking about alliances and that firms could benefit from a new perspective on partnering. This new approach is referred to as High Touch Partnering. The new framework stresses the need for a balanced attention to strategic (re-)positioning, establishing adequate alliance capabilities, building business communities with partners and improved partner selection.

Journal ArticleDOI
TL;DR: In this article, the authors investigated cognitive and behavioral effects of planning (i.e., forming implementation intentions) on goal pursuit during the performance of mundane behaviors and found that participants who formed implementation intentions were more effective in goal pursuit than the control group.
Abstract: The present experiment investigated cognitive and behavioral effects of planning (i.e. forming implementation intentions) on goal pursuit during the performance of mundane behaviors. Participants received the goal to collect a coupon halfway the hall from the lab to the cafeteria. Later, they were also given the task to go from the lab to the cafeteria. Thus participants had to attain a new goal by interrupting a mundane behavior. Some participants enriched their goal with implementation intentions, others did not. Results showed that participants who formed implementation intentions were more effective in goal pursuit than the control group. Importantly, the data suggest that the effects of planning on goal completion are mediated by a heightened mental accessibility of environmental cues related to the goal completion task.

Journal ArticleDOI
TL;DR: A facility location–allocation model for the collection, preprocessing and redistribution of carpet waste is presented and this model differs from other mathematical models for supporting the design of the logistic structure of reuse networks among others in a completely free choice of the locations for pre processing and in explicitly taking into account depreciation costs.

Journal ArticleDOI
TL;DR: The process aspect of E-commerce is stressed by relating it to workflow management by reviewing new and existing architectures to enable interorganizational workflow and focusing on two approaches to partition an interorgan organizational workflow over multiple business partners.

Journal ArticleDOI
TL;DR: A new form of direct subjective presence evaluation that was developed from the method of continuous assessment used to assess television picture quality demonstrated that prior ratings sensitize observers to different features of a display resulting in different presence ratings.
Abstract: We report three experiments using a new form of direct subjective presence evaluation that was developed from the method of continuous assessment used to assess television picture quality. Observers were required to provide a continuous rating of their sense of presence using a handheld slider. The first experiment investigated the effects of manipulating stereoscopic and motion parallax cues within video sequences presented on a 20 in. stereoscopic CRT display. The results showed that the presentation of both stereoscopic and motion parallax cues was associated with higher presence ratings. One possible interpretation of Experiment 1 is that CRT displays that contain the spatial cues of stereoscopic disparity and motion parallax are more interesting or engaging. To test this, observers in Experiment 2 rated the same stimuli first for interest and then for presence. The results showed that variations in interest did not predict the presence ratings obtained in Experiment 1. However, the subsequent ratings of presence differed significantly from those obtained in Experiment 1, suggesting that prior experience with interest ratings affected subsequent judgments of presence. To test this, Experiment 3 investigated the effects of prior experience on presence ratings. Three groups of observers rated a training sequence for interest, presence, and 3-Dness before rating the same stimuli as used for Experiments 1 and 2 for presence. The results demonstrated that prior ratings sensitize observers to different features of a display resulting in different presence ratings. The implications of these results for presence evaluation are discussed, and a combination of more-refined subjective measures and a battery of objective measures is recommended.

Journal ArticleDOI
TL;DR: The parameters proposed quantitatively characterize the RP-HPLC stationary phases and provide a rational explanation for the differences in retention patterns of individual columns observed when applying the conventional empirical testing methods are proposed.

Journal ArticleDOI
TL;DR: In this paper, a constitutive model incorporating a Laplacian of a strain measure and an internal length parameter associated with it is proposed for finite element simulations of localization in a one-dimensional model problem.
Abstract: Combinations of gradient plasticity with scalar damage and of gradient damage with isotropic plasticity are proposed and implemented within a consistently linearized format. Both constitutive models incorporate a Laplacian of a strain measure and an internal length parameter associated with it, which makes them suitable for localization analysis. The theories are used for finite element simulations of localization in a one-dimensional model problem. The physical relevance of coupling hardening/softening plasticity with damage governed by different damage evolution functions is discussed. The sensitivity of the results with respect to the discretization and to some model parameters is analyzed. The model which combines gradient-damage with hardening plasticity is used to predict fracture mechanisms in a Compact Tension test.