Showing papers by "Eindhoven University of Technology published in 2008"

The CMS experiment at the CERN LHC

Abstract: The Compact Muon Solenoid (CMS) detector is described. The detector operates at the Large Hadron Collider (LHC) at CERN. It was conceived to study proton-proton (and lead-lead) collisions at a centre-of-mass energy of 14 TeV (5.5 TeV nucleon-nucleon) and at luminosities up to 10(34)cm(-2)s(-1) (10(27)cm(-2)s(-1)). At the core of the CMS detector sits a high-magnetic-field and large-bore superconducting solenoid surrounding an all-silicon pixel and strip tracker, a lead-tungstate scintillating-crystals electromagnetic calorimeter, and a brass-scintillator sampling hadron calorimeter. The iron yoke of the flux-return is instrumented with four stations of muon detectors covering most of the 4 pi solid angle. Forward sampling calorimeters extend the pseudo-rapidity coverage to high values (vertical bar eta vertical bar <= 5) assuring very good hermeticity. The overall dimensions of the CMS detector are a length of 21.6 m, a diameter of 14.6 m and a total weight of 12500 t.

Strategic niche management and sustainable innovation journeys: Theory, findings, research agenda and policy

Abstract: This article discusses empirical findings and conceptual elaborations of the last 10 years in strategic niche management research (SNM). The SNM approach suggests that sustainable innovation journeys can be facilitated by creating technological niches, i.e. protected spaces that allow the experimentation with the co-evolution of technology, user practices, and regulatory structures. The assumption was that if such niches were constructed appropriately, they would act as building blocks for broader societal changes towards sustainable development. The article shows how concepts and ideas have evolved over time and new complexities were introduced. Research focused on the role of various niche-internal processes such as learning, networking, visioning and the relationship between local projects and global rule sets that guide actor behaviour. The empirical findings showed that the analysis of these niche-internal dimensions needed to be complemented with attention to niche external processes. In this respect, the multi-level perspective proved useful for contextualising SNM. This contextualisation led to modifications in claims about the dynamics of sustainable innovation journeys. Niches are to be perceived as crucial for bringing about regime shifts, but they cannot do this on their own. Linkages with ongoing external processes are also important. Although substantial insights have been gained, the SNM approach is still an unfinished research programme. We identify various promising research directions, as well as policy implications.

Review: Durability and degradation issues of PEM fuel cell components

Abstract: Besides cost reduction, durability is the most important issue to be solved before commercialisation of PEM Fuel Cells can be successful. For a fuel cell operating under constant load conditions, at a relative humidity close to 100% and at a temperature of maximum 75 °C, using optimal stack and flow design, the voltage degradation can be as low as 1–2 μV·h. However, the degradation rates can increase by orders of magnitude when conditions include some of the following, i.e. load cycling, start–stop cycles, low humidification or humidification cycling, temperatures of 90 °C or higher and fuel starvation. This review paper aims at assessing the degradation mechanisms of membranes, electrodes, bipolar plates and seals. By collecting long-term experiments as well, the relative importance of these degradation mechanisms and the operating conditions become apparent.

Inkjet printing as a deposition and patterning tool for polymers and inorganic particles

Abstract: Inkjet printing is an attractive patterning technology, which has become increasingly accepted for a variety of industrial and scientific applications. This review primarily presents an overview of the investigations that have been conducted since 2003 into inkjet-printing polymers or metal-containing inks and mentions related activities. The first section discusses the droplet-formation process in piezoelectric drop-on-demand printheads and the physical properties that affect droplet formation and the resolution of inkjet-printed features. The second section deals with the issues that arise from printing polymers, such as printability and the output characteristics of devices made by this route. Finally, the challenges and achievements attached to inkjet printing metal-containing inks are discussed before concluding with a few remarks about the future of the field.

The acceptance and use of a virtual learning environment in China

Abstract: The success of a virtual learning environment (VLE) depends to a considerable extent on student acceptance and use of such an e-learning system. After critically assessing models of technology adoption, including the Technology Acceptance Model (TAM), TAM2, and the Unified Theory of Acceptance and Usage of Technology (UTAUT), we build a conceptual model to explain the differences between individual students in the level of acceptance and use of a VLE. This model extends TAM2 and includes subjective norm, personal innovativeness in the domain of information technology, and computer anxiety. Data were collected from 45 Chinese participants in an Executive MBA program. After performing satisfactory reliability and validity checks, the structural model was tested with the use of PLS. Results indicate that perceived usefulness has a direct effect on VLE use. Perceived ease of use and subjective norm have only indirect effects via perceived usefulness. Both personal innovativeness and computer anxiety have direct effects on perceived ease of use only. Implications are that program managers in education should not only concern themselves with basic system design but also explicitly address individual differences between VLE users.

Analysis of event-driven controllers for linear systems

Abstract: Most research in control engineering considers periodic or time-triggered control systems with equidistant sample intervals. However, practical cases abound in which it is of interest to consider event-driven control in which the sampling is event-triggered. Although there are various benefits of using event-driven control like reducing resource utilization (e.g., processor and communication load), their application in practice is hampered by the lack of a system theory for event-driven control systems. To provide a first step in developing an event-driven system theory, this paper considers an event-driven control scheme for perturbed linear systems. The event-driven control scheme triggers the control update only when the (tracking or stabilization) error is large. In this manner, the average processor and/or communication load can be reduced significantly. The analysis in this paper is aimed at the control performance in terms of practical stability (ultimate boundedness). Several examples illustrate t...

The acceptance and use of a virtual learning environment in China

Abstract: The success of a virtual learning environment (VLE) depends to a considerable extent on student acceptance and use of such an e-learning system. After critically assessing models of technology adoption, including the Technology Acceptance Model (TAM), TAM2, and the Unified Theory of Acceptance and Usage of Technology (UTAUT), we build a conceptual model to explain the differences between individual students in the level of acceptance and use of a VLE. This model extends TAM2 and includes subjective norm, personal innovativeness in the domain of information technology, and computer anxiety. Data were collected from 45 Chinese participants in an Executive MBA program. After performing satisfactory reliability and validity checks, the structural model was tested with the use of PLS. Results indicate that perceived usefulness has a direct effect on VLE use. Perceived ease of use and subjective norm have only indirect effects via perceived usefulness. Both personal innovativeness and computer anxiety have direct effects on perceived ease of use only. Implications are that program managers in education should not only concern themselves with basic system design but also explicitly address individual differences between VLE users.

Narrow-bandgap diketo-pyrrolo-pyrrole polymer solar cells : the effect of processing on the performance

Abstract: A study has reported on the application of a novel narrow bandgap polymer, poly[3,6-bis-(4'-dodecyl-[2,2']bithiophenyl-5-yl)-2,5-bis-(2-ethyl-hexyl)-2, 5-dihydropyrrolo[3,4-]pyrrole-1,4-dione] (pBBTDPP2) in photovoltaic cells. The conjugated polymer is based on alternating quaterthiophene (BBT) and diketopyrrolo-pyrrole (DPP) units with a bandgap of1.4eV, which is close to the optimum for single, bandgap polymer solar cells. After careful optimization of the processing parameters and morphology, the donor polymer in combination with C60 and C70 PCBM derivatives affords external quantum efficiencies of ~0.4 over a broad spectral range and power conversion efficiencies of 3.2 and 4.0%, respectively under simulated AM1.5G solar light conditions. Significant molecular weights of Mn=20000 and M w=67000g/mol (DPI)=3.35) also were obtained, as determined by gel permeation chromatography (GPC) using 1,2,4-trichlorobenzene as eluent

Semantics and analysis of business process models in BPMN

Abstract: The Business Process Modelling Notation (BPMN) is a standard for capturing business processes in the early phases of systems development. The mix of constructs found in BPMN makes it possible to create models with semantic errors. Such errors are especially serious, because errors in the early phases of systems development are among the most costly and hardest to correct. The ability to statically check the semantic correctness of models is thus a desirable feature for modelling tools based on BPMN. Accordingly, this paper proposes a mapping from BPMN to a formal language, namely Petri nets, for which efficient analysis techniques are available. The proposed mapping has been implemented as a tool that, in conjunction with existing Petri net-based tools, enables the static analysis of BPMN models. The formalisation also led to the identification of deficiencies in the BPMN standard specification.

Forty years of Fanger's model of thermal comfort: comfort for all?

Abstract: The predicted mean vote (PMV) model of thermal comfort, created by Fanger in the late 1960s, is used worldwide to assess thermal comfort. Fanger based his model on college-aged students for use in invariant environmental conditions in air-conditioned buildings in moderate thermal climate zones. Environmental engineering practice calls for a predictive method that is applicable to all types of people in any kind of building in every climate zone. In this publication, existing support and criticism, as well as modifications to the PMV model are discussed in light of the requirements by environmental engineering practice in the 21st century in order to move from a predicted mean vote to comfort for all. Improved prediction of thermal comfort can be achieved through improving the validity of the PMV model, better specification of the model's input parameters, and accounting for outdoor thermal conditions and special groups. The application range of the PMV model can be enlarged, for instance, by using the model to assess the effects of the thermal environment on productivity and behavior, and interactions with other indoor environmental parameters, and the use of information and communication technologies. Even with such modifications to thermal comfort evaluation, thermal comfort for all can only be achieved when occupants have effective control over their own thermal environment.

Post Quantum Cryptography

Abstract: Quantum computers will break today's most popular public-key cryptographic systems, including RSA, DSA, and ECDSA This book introduces the reader to the next generation of cryptographic algorithms, the systems that resist quantum-computer attacks: in particular, post-quantum public-key encryption systems and post-quantum public-key signature systems Leading experts have joined forces for the first time to explain the state of the art in quantum computing, hash-based cryptography, code-based cryptography, lattice-based cryptography, and multivariate cryptography Mathematical foundations and implementation issues are included This book is an essential resource for students and researchers who want to contribute to the field of post-quantum cryptography

Inkjet Printing of Narrow Conductive Tracks on Untreated Polymeric Substrates

Abstract: In the last two decades inkjet printing has grown to a major topic in scientific research, especially drop-on-demand (DOD) inkjet printing systems. DOD inkjet printing has progressed from printing text and graphics, where it started originally, to a tool for (rapid) manufacturing technology. During the last years, the fabrication of narrow conductive tracks by methods of inkjet printing has been investigated extensively. Printing of flexible electronics and minimizing their feature size dramatically lowers the production costs of electronic devices, because material can be positioned on-demand, which reduces the amount of necessary material. The main bottleneck in inkjet-printed features on flexible (polymeric) substrates is the low softening point (Tg) of the substrate, which limits the processing temperature. The Tg of commonly used polymeric substrates, like poly(ethylene terephtalate) (PET) or polycarbonate (PC), is below 150 °C. Typically, colloidal suspensions of conductive materials need a sintering temperature of > 200 °C, which is, hence, not compatible with most polymeric substrates. Feasible products of flexible electronics include, for example, interconnections for circuitry on a printed-circuit board (PCB), electrodes for thin-film transistor (TFT) circuits, organic light-emitting diodes (OLEDs), or disposable displays and radio frequency identification (RFID) tags. Furthermore, printing largearea displays is also a possibility. The typical dimensions of inkjet-printed features depend on the nozzle diameter, and are usually not below 100 lm. The most obvious way to minimize the feature size, that is, line width, is by reducing the nozzle diameter. However, this introduces a narrow window with respect to surface tension and viscosity of the inks, and thereby limits the choice of inks that can be printed. Furthermore, when printing suspensions the particles should be sufficiently smaller than the nozzle diameter; otherwise nozzle clogging occurs. When using piezoelectric-based DOD inkjet printers, smaller droplets can also be produced by modifying the waveform. Much research has been done to predefined (surface energy) patterns on a substrate that forces material to remain in a preferred area on the surface. These techniques rely on the use of expensive masks and conventional photolithography, which increases production costs. Here we present a method to produce narrow conductive silver tracks without prepatterning or modifying the surface energy of the substrate. Preferably, the surface energy should not be too low, because printing on such foils introduces bulges into the printed features, for example with poly(tetrafluorethylene) (PTFE) foils. Line-bulging is an unwanted mechanism that locally broadens the printed structures, as can be seen on the left-hand side of Figure 1. Commonly used polymeric substrates, like PET or polyimide (PI), have a high surface energy, shown on the right-hand side in Figure 1. Although printing on these substrates leads to continuous and straight lines, broad lines are obtained over the whole printed feature, owing to the relatively good wetting of the solvent with the substrate. Clearly, an optimum between surface enerC O M M U N IC A IO N

Cold Atmospheric Plasma: Charged Species and Their Interactions With Cells and Tissues

Abstract: Cold atmospheric plasma (CAP) treatment of living tissues becomes a popular topic in modern plasma physics and in medical sciences. The plasma is capable of bacterial inactivation and noninflammatory tissue modification, which makes it an attractive tool for wound healing and the treatment of skin diseases and dental caries. There are still many open issues with regard to the mechanisms of action of the plasma on bacteria and mammalian cells and tissues, both from the biological and the physical perspective. For example, the chemistry of CAP and the exact roles of various plasma constituents in tissue treatment are not yet fully resolved. In this paper, we shall concentrate on the charged species (electrons and ions) in the plasma. The selected physical properties of typical atmospheric plasma sources will be discussed; experiments will be confronted with theoretical considerations, and several biomedical aspects of CAP treatment will be surveyed.

Searchable Encryption Revisited: Consistency Properties, Relation to Anonymous IBE, and Extensions

Abstract: We identify and fill some gaps with regard to consistency (the extent to which false positives are produced) for public-key encryption with keyword search (PEKS). We define computational and statistical relaxations of the existing notion of perfect consistency, show that the scheme of Boneh et al. (Advances in Cryptology—EUROCRYPT 2004, ed. by C. Cachin, J. Camenisch, pp. 506–522, 2004) is computationally consistent, and provide a new scheme that is statistically consistent. We also provide a transform of an anonymous identity-based encryption (IBE) scheme to a secure PEKS scheme that, unlike the previous one, guarantees consistency. Finally, we suggest three extensions of the basic notions considered here, namely anonymous hierarchical identity-based encryption, public-key encryption with temporary keyword search, and identity-based encryption with keyword search.

Insight into the Mechanisms of Cooperative Self-Assembly: The “Sergeants-and-Soldiers” Principle of Chiral and Achiral C3-Symmetrical Discotic Triamides

Abstract: On the basis of temperature-dependent UV-vis and circular dichroism (CD) spectroscopy measurements, we observed that C3-symmetrical discotic molecules, chiral (R)-1 and achiral 2, both self-assemble in a highly cooperative fashion. Chiral (R)-1 shows a higher degree of cooperativity, meaning it requires a larger nucleus before elongation sets in, as compared to achiral 2. Next to that, we investigated the mechanism of the "sergeants-and-soldiers" principle, where we found that the chiral sergeant (R)-1 strongly amplifies the preference in handedness of the mixed stacks of (R)-1 and 2. However, the elongation temperature and the degree of cooperativity are linearly dependent on both, at least in the regime above 4% of sergeant in the mixed system. Remarkably, we observed that at room temperature a fast exchange on the second time scale exists between molecules and stacks of sergeant (R)-1 and soldier 2, and that interconversion between M and P helices is fast at this temperature.

Surface passivation of high‐efficiency silicon solar cells by atomic‐layer‐deposited Al2O3

Abstract: Atomic-layer-deposited aluminium oxide (Al2O3) is applied as rear-surface-passivating dielectric layer to passivated emitter and rear cell (PERC)-type crystalline silicon (c-Si) solar cells. The excellent passivation of low-resistivity p-type silicon by the negative-charge-dielectric Al2O3 is confirmed on the device level by an independently confirmed energy conversion efficiency of 20·6%. The best results are obtained for a stack consisting of a 30 nm Al2O3 film covered by a 200 nm plasma-enhanced-chemical-vapour-deposited silicon oxide (SiOx) layer, resulting in a rear surface recombination velocity (SRV) of 70 cm/s. Comparable results are obtained for a 130 nm single-layer of Al2O3, resulting in a rear SRV of 90 cm/s. Copyright © 2008 John Wiley & Sons, Ltd.

Superconducting nanowire photon-number-resolving detector at telecommunication wavelengths

Abstract: The drive to develop detectors capable of counting the number of photons in a weak optical pulse is motivated by potential applications in quantum computing. Superconducting nanostructures are one exciting approach: offering high sensitivity and operate at repetition rates up to 80 MHz.

Biomimetic CaCO3 mineralization using designer molecules and interfaces

Abstract: The whole range of organic-inorganic hybrid materials are generally molded into specifically designed devices with fascinating properties that are precisely controlled. The mimicking of the processes involved in biomineralization may provide new approaches to the fabrication of specialized organic-inorganic hybrid materials. Recently, researchers found that the control over polymorphism, crystallographic orientation, and crystal organization are paramount in determining the properties of hybrid materials. In this article, the biomimetic synthesis of calcium carbonate, the most abundant biomineral, has been the main focus.

Twisted Edwards curves

Abstract: This paper introduces "twisted Edwards curves," a generalization of the recently introduced Edwards curves; shows that twisted Edwards curves include more curves over finite fields, and in particular every elliptic curve in Montgomery form; shows how to cover even more curves via isogenies; presents fast explicit formulas for twisted Edwards curves in projective and inverted coordinates; and shows that twisted Edwards curves save time for many curves that were already expressible as Edwards curves.

Projecting Authenticity Through Advertising: Consumer Judgments of Advertisers' Claims

Abstract: Authenticity is a cornerstone of contemporary marketing. Yet how do firms develop brand positions based on authenticity when marketing, and in particular, advertising, is believed to be antithetical to such positioning? We examine how consumers assess the claims of Trappist and Abbey beer brands. We identify three forms of authenticity: pure (literal) authenticity, approximate authenticity, and moral authenticity. In each case, consumers draw on either indexical or iconic cues to form judgments of authenticity, although the type of cue and degree of abstraction differ across the three types. We also find that the informants are duped by careful advertisements, and explain this by proposing that the relationships between indexical and iconic cues are closer than previously thought.

Application of Process Mining in Healthcare – A Case Study in a Dutch Hospital

Abstract: To gain competitive advantage, hospitals try to streamline their pro- cesses. In order to do so, it is essential to have an accurate view of the "careflows" under consideration. In this paper, we apply process mining techniques to obtain meaningful knowledge about these flows, e.g., to discover typical paths followed by particular groups of patients. This is a non-trivial task given the dynamic na- ture of healthcare processes. The paper demonstrates the applicability of process mining using a real case of a gynecological oncology process in a Dutch hos- pital. Using a variety of process mining techniques, we analyzed the healthcare process from three different perspectives: (1) the control flow perspective, (2) the organizational perspective and (3) the performance perspective. In order to do so we extracted relevant event logs from the hospitals information system and ana- lyzed these logs using the ProM framework. The results show that process mining can be used to provide new insights that facilitate the improvement of existing careflows.

Bottom-up organic integrated circuits

Abstract: Self-assembly—the autonomous organization of components into patterns and structures1—is a promising technology for the mass production of organic electronics. Making integrated circuits using a bottom-up approach involving self-assembling molecules was proposed2 in the 1970s. The basic building block of such an integrated circuit is the self-assembled-monolayer field-effect transistor (SAMFET), where the semiconductor is a monolayer spontaneously formed on the gate dielectric. In the SAMFETs fabricated so far, current modulation has only been observed in submicrometre channels3–5, the lack of efficient charge transport in longer channels being due to defects and the limited intermolecular p–p coupling between the molecules in the selfassembled monolayers. Low field-effect carrier mobility, low yield and poor reproducibility have prohibited the realization of bottom-up integrated circuits. Here we demonstrate SAMFETs with long-range intermolecular p–p coupling in the monolayer. We achieve dense packing by using liquid-crystalline molecules consisting of a p-conjugated mesogenic core separated by a long aliphatic chain from a monofunctionalized anchor group. The resulting SAMFETs exhibit a bulk-like carrier mobility, large current modulation and high reproducibility. As a first step towards functional circuits, we combine the SAMFETs into logic gates as inverters; the small parameter spread then allows us to combine the inverters into ring oscillators. We demonstrate real logic functionality by constructing a 15-bit code generator in which hundreds of SAMFETs are addressed simultaneously. Bridging the gap between discrete monolayer transistors and functional selfassembled integrated circuits puts bottom-up electronics in a new perspective.

The effects of transparency on trust in and acceptance of a content-based art recommender

Abstract: The increasing availability of (digital) cultural heritage artefacts offers great potential for increased access to art content, but also necessitates tools to help users deal with such abundance of information. User-adaptive art recommender systems aim to present their users with art content tailored to their interests. These systems try to adapt to the user based on feedback from the user on which artworks he or she finds interesting. Users need to be able to depend on the system to competently adapt to their feedback and find the artworks that are most interesting to them. This paper investigates the influence of transparency on user trust in and acceptance of content-based recommender systems. A between-subject experiment (N = 60) evaluated interaction with three versions of a content-based art recommender in the cultural heritage domain. This recommender system provides users with artworks that are of interest to them, based on their ratings of other artworks. Version 1 was not transparent, version 2 explained to the user why a recommendation had been made and version 3 showed a rating of how certain the system was that a recommendation would be of interest to the user. Results show that explaining to the user why a recommendation was made increased acceptance of the recommendations. Trust in the system itself was not improved by transparency. Showing how certain the system was of a recommendation did not influence trust and acceptance. A number of guidelines for design of recommender systems in the cultural heritage domain have been derived from the study's results.

Three-Port Triple-Half-Bridge Bidirectional Converter With Zero-Voltage Switching

Abstract: A three-port triple-half-bridge bidirectional dc-dc converter topology is proposed in this paper. The topology comprises a high-frequency three-winding transformer and three half-bridges, one of which is a boost half-bridge interfacing a power port with a wide operating voltage. The three half-bridges are coupled by the transformer, thereby providing galvanic isolation for all the power ports. The converter is controlled by phase shift, which achieves the primary power flow control, in combination with pulsewidth modulation (PWM). Because of the particular structure of the boost half-bridge, voltage variations at the port can be compensated for by operating the boost half-bridge, together with the other two half-bridges, at an appropriate duty cycle to keep a constant voltage across the half-bridge. The resulting waveforms applied to the transformer windings are asymmetrical due to the automatic volt-seconds balancing of the half-bridges. With the PWM control it is possible to reduce the rms loss and to extend the zero-voltage switching operating range to the entire phase shift region. A fuel cell and supercapacitor generation system is presented as an embodiment of the proposed multiport topology. The theoretical considerations are verified by simulation and with experimental results from a 1 kW prototype.

Trends, seasonal variability and dominant NOx source derived from a ten year record of NO2 measured from space

Abstract: [1] For the period 1996–2006, global distributions of tropospheric nitrogen dioxide (NO2) have been derived from radiances measured with the satellite instruments GOME (Global Ozone Monitoring Experiment) and SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CartograpHY). A statistical analysis is applied to derive trends and seasonal variability for this period on a global scale. The time series of the monthly NO2 columns for these ten years have been fitted with a linear function superposed on an annual seasonal cycle on a grid with a spatial resolution of 1 by 1 .W e see significant reductions (up to 7% per year) in NO2 in Europe and parts of the eastern United States, and a strong increase in Asia, most particularly in China (up to 29% per year) but also in Iran and Russia. By comparing the data with the cloud information derived from the same satellite observations, the contribution of lightning to the total column of NO2 is estimated. The estimated NO2 from lightning is, especially in the tropics, in good agreement with lightning flash rate observations from space. The satellite observed seasonal variability of NO2 generally correlates well with independent observations and estimates of the seasonal cycle of specific NOx sources. Source categories considered are anthropogenic (fossil fuel and biofuel), biomass burning, soil emissions and lightning. Using the characteristics of the seasonal variability of these source categories, the dominant source of NOx emissions has been identified on a global scale and on a 1 by 1 grid.

Process mining : A two-step approach to balance between underfitting and overfitting

Abstract: Process mining includes the automated discovery of processes from event logs. Based on observed events (e.g., activities being executed or messages being exchanged) a process model is constructed. One of the essential problems in process mining is that one cannot assume to have seen all possible behavior. At best, one has seen a representative subset. Therefore, classical synthesis techniques are not suitable as they aim at finding a model that is able to exactly reproduce the log. Existing process mining techniques try to avoid such "overfitting" by generalizing the model to allow for more behavior. This generalization is often driven by the representation language and very crude assumptions about com- pleteness. As a result, parts of the model are over"fitting" (allow only what has actually been observed) while other parts may be "underfitting" (allow for much more behavior without strong support for it). None of the existing techniques enables the user to control the balance between "overfitting" and "underfitting". To address this, we propose a two-step approach. First, using a configurable approach, a transition system is constructed. Then, using the "theory of regions", the model is synthesized. The approach has been implemented in the context of ProM and overcomes many of the limitations of traditional approaches.