University of Twente Publications
University of Twente Repository provides publications of UT scientific staff, in many cases full text and publicly available.
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Mostrando recursos 1 - 20 de 24,896
Optical response of the sodium alanate system: $GW_0$-BSE calculations and thin film measurements - Setten, M.J. van; Germaud, R.; Brocks, G.; Dam, B.; Kresse, G.; Wijs, G.A. de
We calculate from first principles the optical spectra of the hydrides in the sodium alanate hydrogen storage system: NaH, $NaAlH_4$, and $Na_3AlH_6$. In particular we study the effects of systematic improvements of the theoretical description. To benchmark the calculations we also measure the optical response of a thin film of NaH. The simplest calculated dielectric functions are based upon independent electrons and holes, whose spectrum is obtained at the $G_0W_0$ level. Successive improvements consist of including partial self-consistency (so-called $GW_0$) and account for excitonic effects, using the Bethe-Salpeter equation (BSE). Each improvement gives a sizable blue shift or red shift...
Anomalous anisotropy in athermal Bradley-Harper roughening of Cu(001) - Everts, Frank; Wormeester, Herbert; Poelsema, Bene
Ion bombardment induced surface structures on Cu(001) have been studied under conditions obeying the previously “coined athermal Bradley-Harper (BH) region.” Off-normal ion impact along the ⟨110⟩ and the ⟨100⟩ azimuth at 200 K gives rise to different high-resolution low-energy electron-diffraction patterns. Unanticipated and marked deviations from the inherent fourfold symmetry are obtained already at a polar angle of incidence as low as 10°. Experiments with 800 eV Ar+ ions (flux 6×10 12 ions cm−2 s−1 and fluence 4.3×10 16 ions cm−2) clearly show BH behavior for bombardment along  in contract to bombardment along . This observation is attributed to the higher...
Silicon-based technology for integrated waveguides and mm-Wave systems - Jovanovic, Vladimir; Gentile, Gennaro; Dekker, Ronald; Graaf, Pascal de; Vreede, Leo C.N. de; Nanver, Lis K.; Spirito, Marco
IC processing is used to develop technology for silicon-filled millimeter-wave-integrated waveguides. The frontend process defines critical waveguide sections and enables integration of dedicated components, such as RF capacitors and resistors. Wafer gluing is used to strengthen the mechanical support and deep reactive-ion etching forms the waveguide bulk with smooth and nearly vertical sidewalls. Aluminum metallization covers the etched sidewalls, fully enclosing the waveguides in metal from all sides. Waveguides are fabricated with a rectangular cross section of 560 μm × 280 μm. The measured insertion loss is only 0.12 dB/mm at 105 GHz. The optimized planar transition, the components of...
Boron-doped silicon surfaces from $B_2H_6$ passivated by ALD $Al_2O_3$ for solar cells - Mok, K.R.C. (Caroline); Loo, Bas W.H. van de; Vlooswijk, Ard H.G.; Kessels, W.M.M. (Erwin); Nanver, Lis K.
A p+-doping method for silicon solar cells is presented whereby boron atoms from a pure boron (PureB) layer deposited by chemical vapor deposition using B2H6 as precursor were thermally diffused into silicon. The applicability of this doping process for the doped surfaces of silicon solar cells was evaluated in terms of surface morphology after thermal diffusion, the boron dopant profiles, and sheet resistances, as well as the recombination parameter J0p+, when the doped layers were passivated by Al2O3 films prepared by atomic layer deposition. Adequate surface passivation could be achieved with a surface recombination contribution to J0p+ of <20;fA/cm2 for...
Factors influencing the use of a web-based application for supporting the self-care of patients with type 2 diabetes: a longitudinal study - Nijland, Nicol; Gemert-Pijnen, Julia E.W.C. van; Kelders, Saskia M.; Brandenburg, Bart J.; Seydel, Erwin R.
The take-up of eHealth applications in general is still rather low and user attrition is often high. Only limited information is available about the use of eHealth technologies among specific patient groups.
The aim of this study was to explore the factors that influence the initial and long-term use of a Web-based application (DiabetesCoach) for supporting the self-care of patients with type 2 diabetes.
A mixed-methods research design was used for a process analysis of the actual usage of the Web application over a 2-year period and to identify user profiles. Research instruments included log files, interviews, usability tests, and a survey.
Effectiveness of a web-based intervention aimed at healthy dietary and physical activity behavior: a randomized controlled trial about users and usage - Kelders, Saskia M.; Gemert-Pijnen, Julia E.W.C. van; Werkman, Andrea; Nijland, Nicol; Seydel, Erwin R.
Recent studies have shown the potential of Web-based interventions for changing dietary and physical activity (PA) behavior. However, the pathways of these changes are not clear. In addition, nonusage poses a threat to these interventions. Little is known of characteristics of participants that predict usage.
In this study we investigated the users and effect of the Healthy Weight Assistant (HWA), a Web-based intervention aimed at healthy dietary and PA behavior. We investigated the value of a proposed framework (including social and economic factors, condition-related factors, patient-related factors, reasons for use, and satisfaction) to predict which participants are users and which participants...
Determinants of engagement in face-to-face and online patient support groups - Uden-Kraan, Cornelia F. van; Drossaert, Constance H.C.; Taal, Erik; Smit, Willem M.; Bernelot Moens, Hein J.; Laar, Mart A.F.J. van de
Although peer-to-peer contact might empower patients in various ways, studies show that only a few patients actually engage in support groups.
The objective of our study was to explore factors that facilitate or impede engagement in face-to-face and online peer support, using the Theory of Planned Behavior.
A questionnaire was completed by 679 patients being treated for arthritis, breast cancer, or fibromyalgia at two Dutch regional hospitals.
Our results showed that only a minority of the patients engaged in organized forms of peer support. In total 10% (65/679) of the respondents had engaged in face-to-face meetings for patients in the past year. Only...
A holistic framework to improve the uptake and impact of eHealth technologies - Gemert-Pijnen, Julia E.W.C. van; Nijland, Nicol; Limburg, Maarten van; Ossebaard, Hans C.; Kelders, Saskia M.; Eysenbach, Gunther; Seydel, Erwin R.
Background: Many eHealth technologies are not successful in realizing sustainable innovations in health care practices. One of the reasons for this is that the current development of eHealth technology often disregards the interdependencies between technology, human characteristics, and the socioeconomic environment, resulting in technology that has a low impact in health care practices. To overcome the hurdles with eHealth design and implementation, a new, holistic approach to the development of eHealth technologies is needed, one that takes into account the complexity of health care and the rituals and habits of patients and other stakeholders.
Objective: The aim of this viewpoint paper...
Why business modeling is crucial in the development of eHealth technologies - Limburg, Maarten van; Gemert-Pijnen, Julia E.W.C. van; Nijland, Nicol; Ossebaard, Hans C.; Hendrix, Ron M.G.; Seydel, Erwin R.
The impact and uptake of information and communication technologies that support health care are rather low. Current frameworks for eHealth development suffer from a lack of fitting infrastructures, inability to find funding, complications with scalability, and uncertainties regarding effectiveness and sustainability. These issues can be addressed by defining a better implementation strategy early in the development of eHealth technologies. A business model, and thus business modeling, help to determine such an implementation strategy by involving all important stakeholders in a value-driven dialogue on what the technology should accomplish. This idea also seems promising to eHealth, as it can contribute to...
A competence-based and multidimensional operationalization and measurement of employability - Heijde, Claudia M. van der; Heijden, Beatrice I.J.M. van der
Employability is a critical requirement for enabling both sustained competitive advantage at the firm level and career success at the individual level. We propose a competence-based approach to employability derived from an expansion of the resource-based view of the firm. In this contribution, we present a reliable and valid instrument for measuring employability. This measure is based on a five-dimensional conceptualization of employability, in which occupational expertise is complemented with generic competences. Two sources of raters (employees and their immediate supervisors) are involved in developing and testing the measure. Since the five dimensions of employability explain a significant amount of...
Co-Evolution: Law and Institutions in International Ethics Research - Millar, Carla C.J.M.; Cheng, Philip Y.K.; Choi, Chong-Ju
Despite the importance of the co-evolution approach in various branches of research, such as strategy, organisation theory, complexity, population ecology, technology and innovation (Lewin et al., 1999; March, 1991), co-evolution has been relatively neglected in international business and ethics research (Madhok and Phene, 2001). The purpose of this article is to show how co-evolution theory provides a theoretical framework within which some issues of ethics research are addressed. Our analysis is in the context of the contrasts between business systems (North, 1990), and in particular the distinction between informal systems and those systems where institutions are formalised in law. This...
Use of a genetic algorithm to improve predictions of alternate-bar dynamics - Knaapen, M.A.F.; Hulscher, S.J.M.H.
Alternate bars may form in sandy beds of straight rivers and channels. These bars are characterized by the alternation of crests, all moving downstream at a speed of several meters per day. The aim of this paper is to predict the dynamics of alternate bars. To that end, we tested predictions of measured alternate bars in flume experiments, as derived from an amplitude evolution model. Weakly nonlinear stability analysis underlies this amplitude evolution model, so that it applies to situations in which the width-to-depth ratio is close to the critical ratio, above which alternate bars occur. The experiments have a...
Proximity effect in NiCu-based Josephson tunnel junctions - Latempa, R.; Parlato, L.; Peluso, G.; Pepe, G.P; Ruotolo, A.; Barone, A.; Golubov, A.A.
We present experimental results concerning both the fabrication and the characterization of superconducting tunnel junctions based on Nb/NiCu superconductor/ferromagnet (S/F) bilayers. Josephson junctions have been characterized down to T=1.4 K in terms of current-voltage I-V characteristics, Josephson critical current vs magnetic field, role of external magnetic field. Proximity parameters of the bilayer, such as the coherence length and the exchange field energy of the F metal, have been estimated by means of a numerical deconvolution of the I-V data the electronic density of states on both sides of the S/F bilayer. Results have been compared with theoretical predictions from a...
Het klachtensysteem van de Kijkwijzer: waarom goed niet goed genoeg is - Dorbeck-Jung, Bärbel; Oude Vrielink, Mirjan
Er zijn tal van films, dvd's en televisieseries die schadelijk zijn voor jongeren. Diverse internationale overeenkomsten en nationale wetgeving trachten hiertegen bescherming te bieden. Het Nederlandse stelsel combineert wetgeving met zelfregulering, noodzakelijk vanwege de slechte handhaafbaarheid van rechtsregels. De zelfhandhaving voorziet in een Klachtenrelement dat de inrichting en werking van de klachtenprocedure regelt. ook is een zogeheten Kijkwijzer ontwikkeld. Onderzoekers van de Universiteit Twente (Gosselt, Van Hoof, D. Jong, Dorbeck-Jung en Steehouder) hielden in 2008 in opdracht van het WODC het klachtensysteem en andere aspecten van de zelfregulering tegen het licht.
Bärbel Dorbeck_Jung en Mirjan Oude Vrieling bespreken in dit artikel...
Linking the Value Assessment of Oil and Gas Firms to Ambidexterity Theory Using a Mixture of Normal Distributions - Casault, Sébastien; Groen, Aard J.; Linton, Jonathan D.
Oil and gas exploration and production firms have return profiles that are not easily explained by current financial theory – the variation in their market returns is non-Gaussian. In this paper, the nature and underlying reason for these significant deviations from expected behavior are considered. Understanding these differences in financial market behavior is important for a wide range of reasons, including: assessing investments, investor relations, decisions to raise capital, assessment of firm and management performance. We show that using a “thicker tailed” mixture of two normal distributions offers a significantly more accurate model than the traditionally Gaussian approach in describing...