Determinants and Promotion of Self-Regulated Learning in Educational Contexts: The Potential of Web-based and Attendance-based Courses

Self-regulated learning is an important skill to successfully study at school and university, but it is also of high importance for life-long learning (Commission of the European Community, 2000; Dignath & Büttner, 2008). The aim of this dissertation is to expand the knowledge about the trainability of self-regulated learning. To this end, the effectiveness of a web-based and an attendance-based self-regulated learning-training was compared, the role of individual characteristics as predictors of the effectiveness of self-regulated learning-training was examined, and the possibility of promoting the participation rate in voluntary self-regulated learning-training with minimal interventions was explored. Study I showed that students of an attendance-based and web-based course with the aim of fostering self-regulated learning were very satisfied with both course formats, self-regulated learning was considered useful for studying, and the subjective and objective increases in learning were high. Furthermore, the findings of Study I suggest that self-regulated learning can be fostered in the web-based course as effectively as in the attendance-based course as there were no group differences. Moreover, the findings suggest that it is of relevance to differentiate between two training phases that promote different processes: A theory phase that fosters declarative metacognitive knowledge on self-regulated learning and an implementation phase where strategies of self-regulated learning are practiced. The question of whether the effectiveness of a self-regulated learning-training intervention differs between participants depending on their individual characteristics was investigated in Study II. Results revealed that individual differences in personality – but not motivational factors – were related to the gain of self-regulated learning through respective training in a university context. More precisely, conscientiousness, agreeableness, and openness to experience significantly predicted increases in self-regulated learning, however, with varying importance for the two different phases of the training (theory versus implementation) and the training format (attendance-based versus web-based). Conscientiousness was related to both theory and implementation phases as well as both formats (attendance-based and web-based), agreeableness was only related to the theory phase and to the attendance-based format, and openness was as well only related to the attendance-based format but only in the implementation phase. Finally, while Study I and II were conducted at university, Study III focused on high-school students and addressed the question of whether the participation rate in voluntary web-based self-regulated learning-training can be promoted by minimal interventions on utility value and implementation intention. Unexpectedly, the minimal interventions had no effect on the participation rate, suggesting that these interventions are not effective per se, but rather context dependent. Apart from that, students’ expectation of success and average grade score proved to be positive predictors of training participation, which was also shown by latent profile-analyses. This suggests that initial motivation has an impact on voluntary training participation. In conclusion, the findings of the studies indicate that self-regulated learning can be fostered in web-based and attendance-based formats, that training success of self-regulated learning is related to personality factors, and that motivation plays a role concerning training participation. This dissertation significantly contributes to previous research by showing that both a theory phase and an implementation phase are crucial when employing a training program, and that the extent of training success seems to be affected by personality traits. Moreover, the findings give reason to evaluate critically in which contexts minimal interventions are successful. This dissertation has a number of implications for theory and for future research and it can also provide practical advice for educational contexts

Specific volume of polymers : influence of the thermomechanical history

Nowadays, semi-crystalline polymers are widely used in many product applications that display high dimensional accuracy and stability. However, the relationship between processing conditions and the main property determining macroscopic shrinkage, i.e. specific volume, is still not understood in sufficient detail to predict the resulting dimensions of a product dependent on the selected material and chosen processing conditions. In this thesis, the dependence of the specific volume of crystallizing polymers on the thermomechanical history as experienced during processing is investigated. Emphasis is placed on selecting and reaching those processing conditions that are relevant for industrial processing operations such as injection molding and extrusion. To extent the interpretation of the results obtained on the development of specific volume, structure properties of the resulting crystalline morphology are investigated using wide angle X-ray diffraction (WAXD) in combination with scanning electron microscopy (ESEM). A custom designed dilatometer is presented in chapter 2, which is used to quantitatively analyze the dependence of specific volume on temperature (up to 260 ±C), cooling rate (up to 100 oC/s), pressure (up to 100 MPa), and shear rate (up to 80 1/s). The dilatometer is based on the principle of confined compression, using annular shaped samples with a radial thickness of 0.5 mm. To quantify the measurement error arising from friction forces between the solidifying sample and dilatometer walls, a comparison is made with measurements performed on a dilatometer based on the principle of confining fluid (Gnomix). Measurements performed in the absence of flow, at isobaric conditions, and at a relatively low cooling rate of about 4-5 oC/min agree quite well with respect to the specific volume in the melt, temperature at which the transition to the semi-crystalline state starts, and the specific volume of the solid state. Detailed analysis shows a relative difference in specific volume of the melt of 0.1 - 0.4 %. An identical relative difference is assumed for specific volume measured during the first part of crystallization, since the ratio of shear and bulk modulus is still small and the influence of friction forces and loss of hydrostatic pressure can be neglected. The relative difference in the specific volume of the solid state ranges from 0.1 ¡ 0.2%. However, especially for higher cooling rates, this part of the measured specific volume curve should be taken as qualitative rather than quantitative. The influence of cooling rate on the evolution of specific volume and the resulting crystalline morphology of an isotactic polypropylene is investigated in chapter 3. Experiments performed at cooling rates ranging from 0.1 to 35 oC/s, and elevated pressures ranging from 20 to 60 MPa show a profound influence of cooling rate on the transition temperature, i.e. the temperature at which the transition from the melt to the semi-crystalline state starts, and on the rate of transition. With increasing cooling rate and constant pressure, the transition temperature shifts towards lower temperatures and the transition itself is less distinct and more wide spread. Additionally, an increasing cooling rate causes the final specific volume to increase, which agrees with a decrease in the degree of crystallinity determined from WAXD analysis. For the relatively small pressure range that was experimentally accessible, a combined influence of pressure and cooling rate on the specific volume or crystalline morphology was not found. Experimental validation of numerical predictions of the evolution of specific volume showed at first large deviations in the calculated start and rate of the transition. These deviations increase with increasing cooling rate. Deviations in the rate of transition could partly be explained from small variations in model parameters, and can be justified from possible inaccuracies in the experimental characterization of important input parameters, i.e. the spherulitic growth rate G(T, p) and the number of nuclei per unit volume N(T, p), or from determining model parameters to describe these quantities numerically. Especially in the prediction during fast cooling, G(T, p) and N(T, p) should be characterized for a sufficiently large temperature range, including temperatures typically lower than the temperature where the maximum in G(T, p) occurs. Deviations in predicted transition temperature are however quite unexplained and could only be improved by introducing an unrealistic larger number of nuclei than determined experimentally at relatively high temperatures. This is subject to future investigation. The influence of shear flow on the evolution of the specific volume is investigated in chapter 4. The combined influence of shear rate, pressure and temperature during flow is investigated at non-isothermal conditions using two grades of isotactic polypropylene with different weight averaged molar mass (Mw). In general, shear flow has a pronounced effect on the evolution of specific volume. The temperature marking the transition in specific volume and the rate of transition are affected. The influence of flow increases with increasing shear rate, increasing pressure, decreasing temperature at which flow is applied, and higher Mw. Although the degree of orientation and the overall structure of the resulting crystalline morphology are greatly affected by the flow, the resulting specific volume and degree of crystallinity are only marginally affected by the processing conditions employed. If shear flow is applied at a temperature near the material’s equilibrium melting temperature T0m , i.e. at low undercooling, dependent on material and applied shear rate remelting of flow induced crystalline structures and relaxation of molecular orientation is able to fully erase the effect of flow. With increasing Mw, the effect of flow applied at low undercooling is prevailed longer. Although not investigated in this study, we think that an increased cooling rate (i.e. less time to remelt flow induced structures) would also enlarge the resulting effect on the evolution of specific volume when applied at low undercooling. In chapter 5, the use of the dimensionless Deborah number is investigated to analyze and classify the influence of shear flow on the specific volume and resulting crystalline morphology. Classification of the influence of flow on the orientation of the resulting crystalline morphology as visualized byWAXD could be performed if flow was applied at relatively large undercooling. With increasing Deborah number, the orientation of crystals increases and the classification of the flow strength resulting in a spherulitic, row nucleated, or shish-kebab morphology is possible. However, in case flow was applied at low undercooling, the influence of remelting and relaxation of molecular orientation yields the Deborah number of little use. The influence of flow could be erased totally, even when strong flow is applied, i.e. high Deborah numbers. For large undercooling, remelting and relaxation has little effect on the development of the flow-induced crystalline morphology as was already observed by others. These conclusions also hold for the classification of flow on the evolution of specific volume. If flow is applied at large undercooling, Deborah numbers Des (based on the process of chain retraction) or Derep (based on the process of reptation of chains) can equally well be used to classify the influence of flow on the evolution of specific volume, e.g. characterized by the dimensionless transition temperature µc and dimensionless rate of transition ¸. Even relatively large differences in cooling rate have little effect on the classification of the influence of flow on the evolution of specific volume, when applied at large undercooling. Finally, in chapter 6 the main conclusions of this thesis are outlined together with recommendations for future research

Ritual Identity

Rituals are often used as opportunities for self-reflection and identity construction. The Camino to Santiago de Compostela, which has become a singularly popular pilgrimage since the late 1980s, is an example of a ritual that is explicitly used to gain a deeper understanding of one’s identity through distancing oneself from daily life and creating a space of contemplation. Implicit in this function of rituals in general, and the pilgrimage to Santiago in particular, is the assumption that one is more authentic and closer to one’s true identity during the pilgrimage than one is in daily life. The ritual self, as an idealised identity, functions thus, as a critique of one’s regular cultural identity. This chapter proposes to investigate both the ideal, ritual identity and the implicit critique towards the cultural dynamics that force the pilgrim to ‘not be her/himself’ in daily life