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University of Twente Publications (47,358 recursos)
University of Twente Repository provides publications of UT scientific staff, in many cases full text and publicly available.

Type = Article

Mostrando recursos 1 - 20 de 21,657

1. Translation, cultural adaptation and validation of the WHO fracture risk assessment tool (FRAX®) into Bengali - Islam, Nazrul; Ferdous, Nira; Klooster, Peter M. ten; Uddin, Sheikh Giash; Nasrin, Salma; Pal, Bipasha; Rasker, Johannes J.
Aim To develop a translated and culturally adapted Bengali version of the WHO Fracture Risk Assessment Tool (FRAX®) and to test its feasibility, content validity and reliability. Method The English FRAX was translated and culturally adapted for use in Bangladeshi populations following established forward–backward translation methods and being extensively field-tested. The final version was interviewer-administered to 130 consecutive osteoporotic patients between 40 and 90 years of age. For test–retest reliability, the questionnaire was re-administered after 14 days in 60 odd serial-numbered patients. Results To better match with the Bengali culture, several adaptations were made to the FRAX items, including replacements and additions for tobacco, prednisolone...

2. Trajectories of personal control in cancer patients receiving psychological care - Zhu, Lei; Schroevers, Maya J.; Lee, Marije van der; Garssen, Bert; Stewart, Roy E.; Sanderman, Robbert; Ranchor, Adelita V.
Objective This study aimed to (1) identify subgroups of cancer patients with distinct personal control trajectories during psychological care, (2) examine whether socio-demographic, clinical, and psychological care characteristics could distinguish trajectories, and (3) examine differential patterns of psychological symptoms between trajectories. Methods This naturalistic study focused on 241 cancer patients receiving psychological care at psycho-oncology institutions. Data were collected before the initiation of psychological care, and 3 and 9 months thereafter. Latent class growth analysis was applied to identify personal control trajectories. Results Three personal control trajectories were identified: enduring improvement (41%), temporary improvement (50%), and deterioration (9%). Education and baseline physical symptoms distinguished these...

3. Networks and Networking: The Public Administrative Agendas - O'Toole, Laurence J.
Published in 1997, the article “Treating Networks Seriously: Practical and Research-Based Agendas in Public Administration” outlined the importance of networks for the field of public administration and suggested a series of research agendas that should be pursued. That argument has received substantial attention in the years since. Research on networks and networking has made substantial progress, particularly on some questions—the descriptive agenda, for instance, and some aspects of the practical agenda. However, considerable work remains to be done. More needs to be known about the ways in which networks and networking behavior can shape performance and affect the most salient...

4. A test of the design of a video tutorial for software training - Meij, J. van der; Meij, H. van der
The effectiveness of a video tutorial versus a paper-based tutorial for software training has yet to be established. Mixed outcomes from the empirical studies to date suggest that for a video tutorial to outperform its paper-based counterpart, the former should be crafted so that it addresses the strengths of both designs. This was attempted in the present study. Two consecutive experiments were conducted to examine the effect of tutorial type (video vs. paper based) on task relevance, self-efficacy, mood, flow and task performance. Participants were students from junior high school. Both studies reported significant, positive contributions of the tutorials to...

5. Developing and Testing a Video Tutorial for Software Training - Meij, Hans van der
Purpose: Video tutorials for software training are rapidly becoming popular. A set of dedicated guidelines for the construction of such tutorials was recently advanced in Technical Communication (Van der Meij & Van der Meij, 2013). The present study set out to assess the cognitive and motivational effects of a video tutorial based on these guidelines. Method: Participants were 65 students (mean age 12.0 years) from elementary school. The procedure was as follows. First, students completed a pre-test. Next, they viewed videos and completed practice tasks. Finally, students completed a post-test and retention-test. Results: The pre-test revealed low scores on task...

6. Mechanical Modelling of Pultrusion Process: 2D and 3D Numerical Approaches - Baran, Ismet; Hattel, Jesper H.; Akkerman, Remko; Tutum, Cem C.
The process induced variations such as residual stresses and distortions are a critical issue in pultrusion, since they affect the structural behavior as well as the mechanical properties and geometrical precision of the final product. In order to capture and investigate these variations, a mechanical analysis should be performed. In the present work, the two dimensional (2D) quasi-static plane strain mechanical model for the pultrusion of a thick square profile developed by the authors is further improved using generalized plane strain elements. In addition to that, a more advanced 3D thermo-chemical-mechanical analysis is carried out using 3D quadratic elements which...

7. Pultrusion of a vertical axis wind turbine blade part-II: combining the manufacturing process simulation with a subsequent loading scenario - Baran, Ismet; Tutum, Cem C.; Hattel, Jesper H.; Akkerman, Remko
A novel three dimensional thermo-chemical simulation of the pultrusion process is presented. A simulation is performed for the pultrusion of a NACA0018 blade profile having a curved geometry, as a part of the DeepWind project. The finite element/nodal control volume (FE/NCV) technique is used. First, a pultrusion simulation of a U-shaped composite profile is performed to validate the model and it is found that the obtained cure degree profiles match with those given in the literature. Subsequently, the pultrusion process simulation of the NACA0018 profile is performed. The evolutions of the temperature and cure degree distributions are predicted inside the...

8. Pultrusion of a vertical axis wind turbine blade part-II: combining the manufacturing process simulation with a subsequent loading scenario - Baran, Ismet; Hattel, Jesper H.; Tutum, Cem C.; Akkerman, Remko
This paper in particular deals with the integrated modeling of a pultruded NACA0018 blade profile being a part of EU funded DeepWind project. The manufacturing aspects of the pultrusion process are associated with the preliminary subsequent service loading scenario. A 3D thermo-chemical analysis of the pultrusion process is sequentially coupled with a 2D quasi-static mechanical analysis in which the process induced residual stresses and distortions are predicted using the generalized plane stain elements in a commercial finite element software ABAQUS. The temperature- and cure-dependent resin modulus is implemented by employing the cure hardening instantaneous linear elastic (CHILE) model in the...

9. CARS microscopy as a tool for studying the distribution of micronised drugs in adhesive mixtures for inhalation - Fussell, A.L.; Grasmeijer, F.; Frijlink, H.W.; Boer, A.H. de; Offerhaus, H.L.
Drug particles can be produced in the proper aerodynamic particle size distribution (PSD) for inhalation by techniques such as micronisation or spray drying (1–5 µm). However, mixing with coarse carrier particles may change the PSD by agglomeration. Furthermore, the spatial distribution of the drug particles on the carrier particles in adhesive mixtures is highly relevant to the dispersion performance of inhalation powders. Coherent anti-Stokes Raman scattering (CARS) microscopy is capable of chemically selective imaging, allowing the distribution of drug particles on the surface of carrier particles to be visualised. We used CARS microscopy to image the drug distribution for budesonide and...

10. Alpha-Synuclein oligomers distinctively permeabilize complex model membranes - Stefanovic, A.; Stockl, M.T.; Claessens, M.M.A.E.; Subramaniam, V.
α-Synuclein oligomers are increasingly considered to be responsible for the death of dopaminergic neurons in Parkinson's disease. The toxicity mechanism of α-synuclein oligomers likely involves membrane permeabilization. Even though it is well established that α-synuclein oligomers bind and permeabilize vesicles composed of negatively-charged lipids, little attention has been given to the interaction of oligomers with bilayers of physiologically relevant lipid compositions. We investigated the interaction of α-synuclein with bilayers composed of lipid mixtures that mimic the composition of plasma and mitochondrial membranes. In the present study, we show that monomeric and oligomeric α-synuclein bind to these membranes. The resulting membrane...

11. Optimization of the Thermosetting Pultrusion Process by Using Hybrid and Mixed Integer Genetic Algorithms - Baran, Ismet; Tutum, Cem C.; Hattel, Jesper H.
In this paper thermo-chemical simulation of the pultrusion process of a composite rod is first used as a validation case to ensure that the utilized numerical scheme is stable and converges to results given in literature. Following this validation case, a cylindrical die block with heaters is added to the pultrusion domain of a composite part and thermal contact resistance (TCR) regions at the die-part interface are defined. Two optimization case studies are performed on this new configuration. In the first one, optimal die radius and TCR values are found by using a hybrid genetic algorithm based on a sequential...

12. Reliability Estimation of the Pultrusion Process Using the First-Order Reliability Method (FORM) - Baran, Ismet; Tutum, Cem C.; Hattel, Jesper H.
In the present study the reliability estimation of the pultrusion process of a flat plate is analyzed by using the first order reliability method (FORM). The implementation of the numerical process model is validated by comparing the deterministic temperature and cure degree profiles with corresponding analyses in the literature. The centerline degree of cure at the exit (CDOCE) being less than a critical value and the maximum composite temperature (T max) during the process being greater than a critical temperature are selected as the limit state functions (LSFs) for the FORM. The cumulative distribution functions of the CDOCE and T...

13. Optimum design of pultrusion process via evolutionary multi-objective optimization - Tutum, Cem C.; Baran, Ismet; Deb, Kalyanmoy
Pultrusion is one of the most cost-effective manufacturing techniques for producing fiber-reinforced composites with constant cross-sectional profiles. This obviously makes it more attractive for both researchers and practitioners to investigate the optimum process parameters, i.e., pulling speed, power, and dimensions of the heating platens, length and width of the heating die, design of the resin injection chamber, etc., to provide better understanding of the process, consequently to improve the efficiency of the process as well as the product quality. Using validated computer simulations is “cheap” and therefore is an attractive and efficient tool for autonomous (numerical) optimization. Optimization problems in...

14. DeepWind-from Idea to 5 MW Concept - Paulsen, Uwe S.; Madsen, Helge A.; Kragh, Knud A.; Nielsen, Per H.; Baran, Ismet; Hattel, Jesper; Ritchie, Ewen; Leban, Krisztina; Svendsen, Harald; Berthelsen, Petter A.
The DeepWind concept has been described previously on challenges and potentials, this new offshore floating technology can offer to the wind industry [1]. The paper describes state of the art design improvements, new simulation results of the DeepWind floating vertical axis wind turbine concept, which implies a high potential for cost saving. The most critical aspects of the concept are addressed in proving feasibility, and if it can be scaled up to 20 MW. Applying structural mechanics, generator, floater & mooring system, control system design, and rotor design using detailed integrated models, results have evolved to a 5 MW baseline...

15. The Effect of Product Size on the Pulling Force in Pultrusion - Baran, Ismet; Carlone, Pierpaolo; Hattel, Jesper H.; Palazzo, Gaetano S.; Akkerman, Remko
In the present work, pultrusion of a composite rod is simulated for various part thicknesses using the finite element method. The pultrusion process set-up is taken from literature in which the temperature and the degree of cure evolutions inside the rod were measured. The predicted temperature and degree of cure profiles in the three dimensional (3D) thermo-chemical analysis are found to agree well with the measured data. The contact pressure between the part and the heating die is calculated using a mechanical contact formulation in the 2D mechanical process model for 9 different part thickness values. Using the contact pressure...

16. Investigation of the Spring-In of a Pultruded L-Shaped Profile for Various Processing Conditions and Thicknesses - Baran, Ismet; Hattel, Jesper H.; Akkerman, Remko
In this study, a thermo-mechanical finite element model is developed to predict the spring-in of an industrially pultruded L-shaped profile made of glass/polyester composite. The resin curing kinetics are obtained from the differential scanning calorimetry (DSC) experiments. The development of the resin modulus is derived using the dynamic mechanical analysis (DMA) tests and the effective mechanical properties of the processing composite are calculated using a micromechanical model. The temperature and degree of cure distributions are obtained in a three dimensional (3D) thermo-chemical anlaysis using the finite element method (FEM). The process induced distortions are then calculated using these distributions in...

17. The Effect of Mandrel Configuration on the Warpage in Pultrusion of Rectangular Hollow Profiles - Baran, Ismet; Hattel, Jesper H.; Akkerman, Remko
Thermo-mechanical process simulation of an industrially pultruded rectangular hollow profile is presented. Glass/polyester is used for the continuous filament mat (CFM) and the uni-directional (UD) layers. The process induced residual distortions together with the temperature and degree of cure are predicted using a three dimensional (3D) thermo-chemical model sequentially coupled with a 2D quasi-static generalized plane strain mechanical model. The predicted deformation pattern at the end of the process is found to agree quite well with the one observed for the real pultruded parts in a commercial pultrusion company. In addition, the predicted warpage behaviour is further analysed by adjusting...

18. Service and Life Cycle Management of engineered assets/goods: editorial - Braaksma, A.J.J.

19. Book review "Mario Mendez, The Legal Effects of EU Agreements: Maximalist Treaty Enforcement and Judicial Avoidance Techniques. Oxford: Oxford University Press, 2013" - Wessel, Ramses A.

20. Book review of "Transitioning embedded systems to intelligent environments : a journey through evolving technologies, Satwant Kaur" - Kaffka, Gabi

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