Showing papers by "Eindhoven University of Technology published in 2006"

Advantages and disadvantages of four interview techniques in qualitative research

Abstract: Face-to-face interviews have long been the dominant interview technique in the field of qualitative research. In the last two decades, telephone interviewing became more and more common. Due to the explosive growth of new communication forms, such as computer mediated communication (for example e-mail and chat boxes), other interview techniques can be introduced and used within the field of qualitative research. For a study in the domain of virtual teams, I used various communication possibilities to interview informants as well as face-to-face interviews. In this article a comparison will be made concerning the advantages and disadvantages of face-to-face, telephone, e-mail and MSN messenger interviews. By including telephone and MSN messenger interviews in the comparison, the scope of this article is broader than the article of BAMPTON and COWTON (2002).

Probing the Solvent-Assisted Nucleation Pathway in Chemical Self-Assembly

Abstract: Hierarchical self-assembly offers a powerful strategy for producing molecular nanostructures. Although widely used, the mechanistic details of self-assembly processes are poorly understood. We spectroscopically monitored a nucleation process in the self-assembly of p-conjugated molecules into helical supramolecular fibrillar structures. The data support a nucleation-growth pathway that gives rise to a remarkably high degree of cooperativity. Furthermore, we characterize a helical transition in the nucleating species before growth. The self-assembly process depends strongly on solvent structure, suggesting that an organized shell of solvent molecules plays an explicit role in rigidifying the aggregates and guiding them toward further assembly into bundles and/or gels.

Molecular machines: nanomotor rotates microscale objects.

Abstract: A molecular motor in a liquid-crystal film uses light to turn items thousands of times larger than itself.

Network Embeddedness and the Exploration of Novel Technologies: Technological Distance, Betweenness Centrality and Density

Abstract: In this paper we analyze the innovative performance of alliance networks as a function of the technological distance between partners, a firm's network position (centrality) and total network density. We study how these three elements of an alliance network, apart and in combination, affect the 'twin tasks' in exploration, namely novelty creation on the one hand and its efficient absorption on the other hand. For an empirical test, we study technology-based alliance networks in the pharmaceutical, chemical and automotive industry.

Ink‐jet Printing and Microwave Sintering of Conductive Silver Tracks

Abstract: Printing techniques, such as ink-jet printing, are interesting alternatives to conventional photolithography for the production of electronic devices. The advantages of printing include the ease of mass production, low cost, and flexibility. Compared to other printing techniques (e.g., screen printing), ink-jet printing does not offer the same production speed. However, the unprecedented flexibility of ink-jet printing makes it very well suited for rapid prototyping applications. In addition, it allows the use of inviscid fluids, such as dilute polymer solutions or suspensions without added binders. A typical application involves the ink-jet printing of conductive tracks, for example, by using inks based on (in)organic silver or copper precursors. The precursor is reduced to the corresponding metal via a post-printing thermal annealing step. In most cases, however, the ink is a dispersion of noble-metal nanoparticles, usually silver or gold. A sintering step is necessary to render the tracks conductive. The use of nanoparticles reduces the sintering temperature due to their high surface to volume ratio. In the past, two different techniques have been used to sinter printed nanoparticle structures. Conventional radiation– conduction–convection heating is the most commonly used method, wherein the sintering temperatures are typically above 200 °C. Therefore many potentially interesting substrate materials, such as thermoplastic polymers or paper, cannot be used. In fact, one of the very few, if not the only organic substrate that can be used is (expensive) polyimide (PI). The long sintering times required—usually 60 min or more— also imply that the technique is not feasible for fast industrial production. As an alternative, a laser sintering method was developed. The laser follows the conductive tracks and sinters these selectively, without affecting the substrate. However, this method is costly and complex from a technical point of view. Thus, there is a clear need for a fast, simple, and costeffective technique that would allow the sintering of the printed structures by the selective heating of only the printed components. Microwave heating fulfills these requirements. Microwave heating is widely used for the sintering of dielectric materials and in synthetic chemistry. It offers advantages such as uniform, fast, and volumetric heating. Microwave radiation is absorbed due to coupling with charge carriers or rotating dipoles. The absorbed power per unit volume P is,

Non-linearity and Expectations in Niche-Development Trajectories: Ups and Downs in Dutch Biogas Development (1973–2003)

Abstract: Non-linearity and changes in the direction of technological trajectories, are related to changes in cognitive rules and expectations that guide technical search and development activities. To explain such changes, the article uses the literature on niche development, which highlights interactions between learning processes, network building and expectations. A long-term case study on Dutch biogas development illustrates how these interactions explain non-linearity, but the case study also shows the importance of external regime dynamics. It is concluded that non-linearity and changes in niche expectations are related to both internal learning processes and external developments.

A declarative approach for flexible business processes management

Abstract: Management of dynamic processes in an important issue in rapidly changing organizations. Workflow management systems are systems that use detailed process models to drive the business processes. Current business process modelling languages and models are of imperative nature – they strictly prescribe how to work. Systems that allow users to maneuver within the process model or even change the model while working are considered to be the most suitable for dynamic processes management. However, in many companies it is not realistic to expect that end-users are able to change their processes. Moreover, the imperative nature of these languages forces designer to over-specify processes, which results in frequent changes. We propose a fundamental paradigm shift for flexible process management and propose a more declarative approach. Declarative models specify what should be done without specifying how it should be done. We propose the ConDec language for modelling and enacting dynamic business processes. ConDec is based on temporal logic rather than some imperative process modelling language.

Hybrid Solar Cells from Regioregular Polythiophene and ZnO Nanoparticles

Abstract: Blends of nanocrystalline zinc oxide nanoparticles (nc-ZnO) and regioregular poly(3-hexylthiophene) (P3HT) processed from solution have been used to construct hybrid polymer–metal oxide bulk-heterojunction solar cells. Thermal annealing of the spin-cast films significantly improves the solar-energy conversion efficiency of these hybrid solar cells to ∼ 0.9 %. Photoluminescence and photoinduced absorption spectroscopy demonstrate that charge-carrier generation is not quantitative, because a fraction of P3HT appears not to be in contact with or in close proximity to ZnO. The coarse morphology of the films, also identified by tapping-mode atomic force microscopy, likely limits the device performance.

Lipid-based nanoparticles for contrast-enhanced MRI and molecular imaging.

Abstract: In the field of MR imaging and especially in the emerging field of cellular and molecular MR imaging, flexible strategies to synthesize contrast agents that can be manipulated in terms of size and composition and that can be easily conjugated with targeting ligands are required. Furthermore, the relaxivity of the contrast agents, especially for molecular imaging applications, should be very high to deal with the low sensitivity of MRI. Lipid-based nanoparticles, such as liposomes or micelles, have been used extensively in recent decades as drug carrier vehicles. A relatively new and promising application of lipidic nanoparticles is their use as multimodal MR contrast agents. Lipids are amphiphilic molecules with both a hydrophobic and a hydrophilic part, which spontaneously assemble into aggregates in an aqueous environment. In these aggregates, the amphiphiles are arranged such that the hydrophobic parts cluster together and the hydrophilic parts face the water. In the low concentration regime, a wide variety of structures can be formed, ranging from spherical micelles to disks or liposomes. Furthermore, a monolayer of lipids can serve as a shell to enclose a hydrophobic core. Hydrophobic iron oxide particles, quantum dots or perfluorocarbon emulsions can be solubilized using this approach. MR-detectable and fluorescent amphiphilic molecules can easily be incorporated in lipidic nanoparticles. Furthermore, targeting ligands can be conjugated to lipidic particles by incorporating lipids with a functional moiety to allow a specific interaction with molecular markers and to achieve accumulation of the particles at disease sites. In this review, an overview of different lipidic nanoparticles for use in MRI is given, with the main emphasis on Gd-based contrast agents. The mechanisms of particle formation, conjugation strategies and applications in the field of contrast-enhanced, cellular and molecular MRI are discussed.

Stressors, Resources, and Strain at Work: A Longitudinal Test of the Triple-Match Principle.

Abstract: Two longitudinal studies investigated the issue of match between job stressors and job resources in the prediction of job-related strain. On the basis of the triple-match principle (TMP), it was hypothesized that resources are most likely to moderate the relation between stressors and strains if resources, stressors, and strains all match. Resources are less likely to moderate the relation between stressors and strains if (a) only resources and stressors match, (b) only resources and strains match, or (c) only stressors and strains match. Resources are least likely to moderate the relation between stressors and strains if there is no match among stressors, resources, and strains. The TMP was tested among 280 and 267 health care workers in 2 longitudinal surveys. The likelihood of finding moderating effects was linearly related to the degree of match, with 33.3% of all tested interactions becoming significant when there was a triple match, 16.7% when there was a double match, and 0.0% when there was no match. Findings were most consistent if there was an emotional match or a physical match.

Family of multiport bidirectional DC¿DC converters

Abstract: Multiport DC-DC converters are of potential interest in applications such as generation systems utilising multiple sustainable energy sources. A family of multiport bidirectional DC-DC converters derived from a general topology is presented. The topology shows a combination of DC-link and magnetic coupling. This structure makes use of both methods to interconnect multiple sources without the penalty of extra conversion or additional switches. The resulting converters have the advantage of being simple in topology and have a minimum number of power devices. The proposed general topology and basic cells show several possibilities to construct a multiport converter for particular applications and provide a solution to integrate diverse sources owing to their flexibility in structure. The system features a minimal number of conversion steps, low cost and compact packaging. In addition, the control and power management of the converter by a single digital processor is possible. The centralised control eliminates complicated communication structures that would be necessary in the conventional structure based on separate conversion stages. A control strategy based on classical control theory is proposed, showing a multiple PID-loop structure. The general topology and a set of three-port embodiments are detailed.

Quantum dots with a paramagnetic coating as a bimodal molecular imaging probe

Abstract: MRI detectable and targeted quantum dots were developed. To that aim, quantum dots were coated with paramagnetic and pegylated lipids, which resulted in a relaxivity, r(1), of nearly 2000 mM(-1)s(-1) per quantum dot. The quantum dots were functionalized by covalently linking alphavbeta3-specific RGD peptides, and the specificity was assessed and confirmed on cultured endothelial cells. The bimodal character, the high relaxivity, and the specificity of this nanoparticulate probe make it an excellent contrast agent for molecular imaging purposes.

Mechanism and kinetics of dithiobenzoate-mediated RAFT polymerization. I. The current situation

Abstract: Investigations into the kinetics and mechanism of dithiobenzoate-mediated Reversible Addition-Fragmentation Chain Transfer (RAFT) polymerizations, which exhibit nonideal kinetic behavior, such as induction periods and rate retardation, are comprehensively reviewed. The appreciable uncertainty in the rate coefficients associated with the RAFT equilibrium is discussed and methods for obtaining RAFT-specific rate coefficients are detailed. In addition, mechanistic studies are presented, which target the elucidation of the fundamental cause of rate retarding effects. The experimental and theoretical data existing in the literature are critically evaluated and apparent discrepancies between the results of different studies into the kinetics of RAFT polymerizations are discussed. Finally, recommendations for further work are given. (c) 2006 Wiley Periodicals, Inc.

On the suitability of BPMN for business process modelling

Abstract: In this paper we examine the suitability of the Business Process Modelling Notation (BPMN) for business process modelling, using the Workflow Patterns as an evaluation framework. The Workflow Patterns are a collection of patterns developed for assessing control-flow, data and resource capabilities in the area of Process Aware Information Systems (PAISs). In doing so, we provide a comprehensive evaluation of the capabilities of BPMN, and its strengths and weaknesses when utilised for business process modelling. The analysis provided for BPMN is part of a larger effort aiming at an unbiased and vendor-independent survey of the suitability and the expressive power of some mainstream process modelling languages. It is a sequel to previous work in which languages including BPEL and UML Activity Diagrams were evaluated.

Usefulness of DC power flow for active power flow analysis with flow controlling devices

Abstract: DC power flow is a commonly used tool for contingency analysis. Recently, due to its simplicity and robustness, it also becomes increasingly used for the real-time dispatch and techno-economic analysis of power systems. It is a simplification of a full power flow looking only at active power. Aspects such as voltage support and reactive power management are possible to analyse. However, such simplifications cannot always be justified and sometimes lead to unrealistic results. Especially the implementation of power flow controlling devices is not trivial since standard DC power flow fundamentally neglects their effects. Until recently, this was not an issue as the application of power flow controlling devices in the European grid was limited. However, with the liberalisation of European electricity market and the introduction of large wind energy systems, the need for real power flow control has emerged and therefore, the use of these devices has been reconsidered. Several phase shifting transformers (PST) are being installed or planned in order to control flows. Therefore, it is important to fundamentally re-validate the fast, but less accurate, DC power flow method. In this paper the assumptions of DC power flow are analysed, and its validity is assessed by comparing the results of power flow simulations using both the DC and AC approaches on a modified IEEE 300 bus system with PSTs.

DecSerFlow: towards a truly declarative service flow language

Abstract: The need for process support in the context of web services has triggered the development of many languages, systems, and standards. Industry has been developing software solutions and proposing standards such as BPEL, while researchers have been advocating the use of formal methods such as Petri nets and π-calculus. The languages developed for service flows, i.e., process specification languages for web services, have adopted many concepts from classical workflow management systems. As a result, these languages are rather procedural and this does not fit well with the autonomous nature of services. Therefore, we propose DecSerFlow as a Declarative Service Flow Language. DecSerFlow can be used to specify, enact, and monitor service flows. The language is extendible (i.e., constructs can be added without changing the engine or semantical basis) and can be used to enforce or to check the conformance of service flows. Although the language has an appealing graphical representation, it is grounded in temporal logic.

Plasma needle for in vivo medical treatment: recent developments and perspectives

Abstract: In this paper we describe the hitherto unravelled facts on the interactions of a cold atmospheric plasma with living cells and tissues. A specially designed source, plasma needle, is a low-power discharge, which operates under the threshold of tissue damage. When applied properly, the needle does not cause fatal cell injury which would result in cell death (necrosis). Instead, it allows precise and localized cell removal by means of the so-called cell detachment. In addition, plasma can be used for bacterial disinfection. Because of mild treatment conditions, plasma disinfection can be performed in vivo, e.g. on wounds and dental cavities. Presently, one strives to obtain a better control of the operating device. Therefore, plasma has been characterized using a variety of diagnostics, and a smart system has been designed for the positioning of the device with respect to the treated surface.

Fiber to the Home/Fiber to the Premises: What, Where, and When?

Abstract: After conquering the core and metropolitan networks, fiber is now penetrating into the access domain. Its low loss and huge bandwidth enable the delivery of any current and foreseeable set of broadband services, and also make it a nice match to the wireless link to the end user. Cost effectiveness is a key issue, and will be decisive for the network topology choices. Point-to-point may be the most cost-effective for short-reach access, whereas point-to-multipoint may be the most interesting at medium- to long-reach access, or when line terminations in the local exchange become a key issue. A number of optical techniques being deployed for shared-fiber multiple access are discussed, based on time slot multiplexing, frequency slot multiplexing, code division multiplexing, and wavelength multiplexing, including their application in fiber to the home/fiber to the premises (FTTH/FTTP) networks for fast data transfer (asynchronous transfer mode (ATM) or Ethernet based) and for broadband service distribution (such as CATV). In the research laboratories, techniques aiming at next-generation optical access are being studied, such as wavelength routing for flexible capacity allocation and easily adaptable hosting of services and service providers, and radio-over-fiber techniques creating a powerful symbiosis of the fiber world and the wireless world by enabling centralized radio signal processing

Older adults' motivated choice for technological innovation: evidence for benefit-driven selectivity.

Abstract: This study examined older adults' motivation to adopt technological innovation. Sixty-eight older e-mail users and nonusers discussed the use of e-mail and of traditional communication methods in 18 focus groups. The results show older adults' benefit-driven approach to new communication technology. Regardless of whether their decision about the new technology was positive or negative and irrespective of their e-mail experience, participants focused on benefits rather than costs. For traditional media, both costs and benefits were important. Results contradict the common belief that barriers such as usability problems determine whether older people use new technology and indicate the decisive role of perceived benefits for successful innovation.

Decision mining in prom

Abstract: Process-aware Information Systems typically log events (e.g., in transaction logs or audit trails) related to the actual business process executions. Proper analysis of these execution logs can yield important knowledge that can help organizations to improve the quality of their services. Starting from a process model, which can be discovered by conventional process mining algorithms, we analyze how data attributes influence the choices made in the process based on past process executions. Decision mining, also referred to as decision point analysis, aims at the detection of data dependencies that affect the routing of a case. In this paper we describe how machine learning techniques can be leveraged for this purpose, and we present a Decision Miner implemented within the ProM framework.