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325 research outputs found

Microwave Photonic Signal Processing Using On-Chip Nonlinear Optics

Author: Hout R.W.N.M. van
Rietveld A.C.M.
Publication venue: Faculty of Science, School of Physics
Publication date: 01/01/2015
Field of study

The field of microwave photonics (MWP) emerged as a solution to the challenges faced by electronic systems when dealing with high-bandwidth RF and microwave signals. Photonic devices are capable of handling immense bandwidths thanks to the properties of light. MWP therefore employs such devices to process and distribute the information carried by RF and microwave signals, enabling significantly higher capacity compared to conventional electronics. The photonic devices traditionally used in MWP circuits have mainly comprised bulky components, such as spools of fibre and benchtop optical amplifiers. While achieving impressive performance, these systems were not capable of competing with electronics in terms of size and portability. More recently, research has focused on the application of photonic chip technology to the field of MWP in order to reap the benefits of integration, such as reductions in size, weight, cost, and power consumption. Integrated MWP however is still in its infancy, and ongoing research efforts are exploring new ways to match integrated photonic devices to the unique requirements of MWP circuits. This work investigates the application of on-chip nonlinear optical interactions to MWP. Nonlinear optics enables light-on-light interactions (not normally possible in a linear regime) which open a vast array of powerful functionalities. In particular, this thesis focuses on stimulated Brillouin scattering, resulting from the interaction of light with hypersonic sound waves, and four-wave mixing, where photons exchange energies. These two nonlinear effects are applied to implement MWP ultra-high suppression notch filters, wideband phase shifters, and ultra-fast instantaneous frequency measurement systems. Experimental demonstrations using integrated optical waveguides confirm record results

Sydney eScholarship

The role of self-concept content, certainty and stability in academic procrastination

Author: Bart I.E.
Hout R.W.N.M. van
Schabos Y.
Vries E de
Publication venue: Faculty of Science, School of Psychology
Publication date: 01/01/2014
Field of study

Academic procrastination has been associated with a variety of negative outcomes. While theorists have proposed that those with an unstable self-concept engage in procrastination due to the fear that they will be unable to meet the required standard, a systematic review conducted as part of the present study (Chapter 2) revealed that all research pertaining to the self-concept in academic procrastination has been correlational, thereby limiting the validity of such theories. As such, the present study employed an experimental design to investigate the self-concept of academic procrastinators (Chapter 3). Ninety-nine undergraduate students completed trait, symptom and academic procrastination inventories as well as measures of state-based affect and cognition, and self-concept content, certainty and stability before and after receiving feedback for a writing task. Compared to low procrastinators, high procrastinators described a self-concept characterised by a greater number of negative and procrastination-related attributes, higher levels of fear of negative evaluation, lower levels of self-concept clarity, self-efficacy and self-esteem and more severe symptoms of depression, anxiety and stress. Furthermore, both the content and certainty associated with procrastinators’ self-concept descriptions changed significantly as a result of receiving randomly allocated feedback for a writing task. While high procrastinators reported significant improvements to their self-concept after receiving a positive evaluation, low procrastinators showed a more positive self-concept which did not change after feedback. These results provide the first empirical evidence for the presence of an unstable self-concept in academic procrastinators, providing support for the aforementioned theory and emphasising the importance of addressing self-concept stability in the psychological treatment of academic procrastination. Further research may investigate mindfulness-based interventions

Sydney eScholarship

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