Transition of planar Couette flow at infinite Reynolds numbers

An outline of the state space of planar Couette flow at high Reynolds numbers (Re<105) is investigated via a variety of efficient numerical techniques. It is verified from nonlinear analysis that the lower branch of the hairpin vortex state (HVS) asymptotically approaches the primary (laminar) state with increasing Re. It is also predicted that the lower branch of the HVS at high Re belongs to the stability boundary that initiates a transition to turbulence, and that one of the unstable manifolds of the lower branch of HVS lies on the boundary. These facts suggest HVS may provide a criterion to estimate a minimum perturbation arising transition to turbulent states at the infinite Re limit. © 2013 American Physical Society.

Specialist business skills of international students

This paper follows on from that presented at the last BEST conference in Edinburgh (Higson & Hamilton-Jones(2004)). At that stage, the authors outlined their initial research work with students studying on the yearlong International Foundation programmes. at three local FE Colleges allied to Aston University. The research (funded by the University's Teaching Quality Enhancement Funds (TQEF) involved questionnaires and interviews with staff and students (the latter all from overseas). it aimed to identify ways to improve the learning experience of students on the International Foundation programmes, to aid their smooth transition to full degree programmes in Business and Management and to improve the progression rates of such students while studying at Aston. The initial research findings were used to design a module for those students' progress to degree programmes in Aston Business School. This paper discusses how the module was designed, its content and the assessment methods used to help determine whether students are achieving the learning outcomes. The basic principle was to identify areas of study where the International Foundation Programme students needed help in order to improve their learning styles to assist them with the requirements of other modules that they would be studying during their time at Aston. Particular emphasis was put on the need to develop active learners who were not disadvantaged by their lack of awareness of UK culture and society and who were as comfortable performing written work under examination conditions or presenting orally as their UK counterparts. An additional aim was to prepare these students for the placement year which was a compulsory part of their degree. The module, therefore, comprises a range of inputs for a number of staff, a company visit, weekly reflective learning leading to Personal Development Plan (PDP) work, formal examinations, presentations, group work •and individual case studies. This paper also reports on the initial reaction of the students and tutors to the new learning experience with currently 30 participants undertaking the module. Provisional findings suggest that the International Foundation programme has prepared the students well for degree-level work and that as a group of international students they are much more analytical and, after studying the module interactive than their counterparts who have come directly onto Aston degrees. It has shown them still to be quite passive learners, comfortable with facts and lecture-style learning environments, but less comfortable when asked to use their own initiatives. Continuing progress needs to be made in terms of encouraging them to develop a reflective approach to learning with the students taking some time to feel comfortable with an analytical approach to learning. In addition, im account of the students' reactions to having to work through a formal (PDP) and the results of their first assessments will be provided. At Aston, this work is being used as a pilot to recognise good practice with regards to work with further groups of international students. it is hoped that this would have widespread application across the sector.

Unveiling temporal correlations characteristic of a phase transition in the output intensity of a fiber laser

We use advanced statistical tools of time-series analysis to characterize the dynamical complexity of the transition to optical wave turbulence in a fiber laser. Ordinal analysis and the horizontal visibility graph applied to the experimentally measured laser output intensity reveal the presence of temporal correlations during the transition from the laminar to the turbulent lasing regimes. Both methods unveil coherent structures with well-defined time scales and strong correlations both, in the timing of the laser pulses and in their peak intensities. Our approach is generic and may be used in other complex systems that undergo similar transitions involving the generation of extreme fluctuations.

Transition dynamics for multi-pulsing in mode-locked lasers

We consider experimentally and theoretically a refined parameter space in a mode-locked fiber laser near the transition to multi-pulsing. Increasing cavity energy drives the dynamics through a periodic instability to chaotic dynamics. © 2010 Optical Society of America.

Characterizing the transition dynamics for multi-pulsing in mode-locked lasers

We consider experimentally and theoretically a refined parameter space near the transition to multi-pulse modelocking. Near the transition, the onset of instability is initiated by a Hopf (periodic) bifurcation. As cavity energy is increased, the band of unstable, oscillatory modes generates a chaotic behavior between single- and multi-pulse operation. Both theory and experiment are in good qualitative agreement and they suggest that the phenomenon is of a universal nature in mode-locked lasers at the onset of multi-pulsing from N to N + 1 pulses per round trip. This is the first theoretical and experimental characterization of the transition behavior, made possible by a highly refined tuning of the gain pump level. © 2010 Copyright SPIE - The International Society for Optical Engineering.