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Contains fulltext : 64476.pdf (publisher's version ) (Closed access), This study examined the structure of occupational well-being among 1,252 Dutch teachers. Building on Warr (1994) and Ryff (1989), a multidimensional model for occupational well-being (including affective, cognitive, professional, social and psychosomatic dimensions) was proposed and tested. Confirmatory factor analysis supported the distinction between these dimensions. A second-order factor analysis revealed that affect was the most central dimension, supporting earlier conceptualizations of subjective well-being that mainly focused on affect.

Item does not contain fulltext, The job demands-resources (JD-R) model was tested in a study among 3,092 employees working in 1 of 4 different home care organizations. The central assumption in the model is that burnout develops when certain job demands are high and when job resources are limited because such negative working conditions lead to energy depletion and undermine worker motivation and learning opportunities, respectively. A series of multigroup structural equation modeling analyses provide strong evidence for the JD-R model. Specifically, results showed that job demands are primarily and positively related to the exhaustion component of burnout, whereas job resources are primarily related to cynicism (negatively) and professional efficacy (positively). The theoretical and practical implications of the JD-R model are discussed.

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Item does not contain fulltext, This study evaluated the effectiveness of a large-scale job stress reduction program implemented in the Dutch domiciliary care sector. The employees of 81 organizations were interviewed twice (only nurses in executive jobs; total sample size exceeded 26,000). Organizations that implemented many interventions were expected to be more successful in reducing job stress than were other organizations. It was found that (a) levels of job stress decreased during the observed interval; (b) organizations with many suboptimal scores on selected work characteristics took, on average, more measures to reduce job stress than others; (c) organizations usually implemented a wide variety of measures; and (d) work-directed (but not other) interventions were linked to job stress reduction. The effects of these interventions, however, were weak.

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Item does not contain fulltext, This study examined the antecedents of job strain (emotional exhaustion, health complaints) and withdrawal behaviour (e.g. lowered organizational commitment) among a cross-sectional sample of 131 academic staff members of the law department of a large Dutch university. Conservation of resources theory (Hobfoll, 1989) provided the theoretical background for this study. Strains and withdrawal behaviours were expected to be most prominent among those who reported having few resources and/or who reported high job demands. Structural equation modelling revealed that this was indeed the case. As predicted, differential patterns of effects emerged for job demands and job resources. Analysis of the effects of four job-specific stressors revealed that especially the structural aspects of a staff member's teaching task (e.g. the number of students in their classes) contributed strongly to perceived job demands. Theoretical and practical implications of the study are discussed.

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A technique is presented which can be used to measure the interfacial normal strength in transversely loaded composites. The technique combines the measurement of local deformations during tests in a Scanning Electron Microscope and numerical simulations, in which the measurements are used as boundary conditions. Deformations are measured by placing a grid of markers on the surface of single fibre specimens. The displacements of these markers are measured during loading of the specimen. Numerical simulations show that the radial and tangential interface stresses increase towards the specimen surface, causing the initiation of debonding at the surface. This effect is supported by tests under an optical microscope. The interfacial normal strength is defined to be the maximum radial interface stress just before the initiation of debonding. Based on the presented results, it can be concluded that the presented technique is a promising tool for the measurement of the interfacial normal stress.

This paper presents a control law for shape memory alloy (SMA) wire actuators. Unlike most laws reported in the literature, this control law includes both a feedback and an open-loop part. The open-loop part takes into account the stress - strain - temperature behaviour of SMA wires, as well as the dynamics of the heating and cooling process. A constitutive model for a NiTi wire is developed. This model is a compromise between accurate description of the real behaviour, and simplicity, since it must be used on-line for the determination of the open-loop part of the control law. The method is tested both in simulations and experiments on a system with one degree of freedom. The tracking performance of the controlled system was investigated for a number of trajectory-following tasks. The tracking error obtained with the proposed control method is considerably smaller than with feedback control only.

A mixed experimental—numerical method is presented which can be used to characterize interphases in composite materials. This method is marked by using measured field quantities, such as displacements and strains, and finite element simulations of the experiments to fit interphase parameters using an iterative minimum variance estimation algorithm. Field quantities are measured using marker fields in the vicinity of the interphase. The markers are applied using the electron beam of a scanning electron microscope (SEM). A marker grid, consisting of dots with a diameter of 0.2 µm, is placed on the surface of unidirectional glass fibre-reinforced epoxies. The displacement field is determined by calculating the relative displacements of the markers during transverse tensile experiments in a SEM. Subsequently, the experiment is modelled using the finite element method. The positions of the border markers of the marker grid define the geometry of the model, and the displacements of these markers the boundary conditions. A mathematical interphase model is included. The parameters, quantifying the mechanical behaviour of the interphase, are fitted using the iterative parameter estimation procedure. Based on the presented results, it can be concluded that the method is a promising tool for the characterization of interphases.