Coherent structures in localised and global pipe turbulence

The recent discovery of unstable travelling waves (TWs) in pipe flow has been hailed as a significant breakthrough with the hope that they populate the turbulent attractor. We confirm the existence of coherent states with internal fast and slow streaks commensurate in both structure and energy with known TWs using numerical simulations in a long pipe. These only occur, however, within less energetic regions of (localized) `puff' turbulence at low Reynolds numbers (Re=2000-2400), and not at all in (homogeneous) `slug' turbulence at Re=2800. This strongly suggests that all currently known TWs sit in an intermediate region of phase space between the laminar and turbulent states rather than being embedded within the turbulent attractor itself. New coherent fast streak states with strongly decelerated cores appear to populate the turbulent attractor instead.Comment: As accepted for PRL. 4 pages, 6 figures. Alterations to figs. 4,5. Significant changes to tex

Gas core rocket reactors - A new look

Feasibility analysis of open-cycle gas-core nuclear rocket engin

Encapsulation task of the low-cost silicon solar array project. Investigation of test methods, material properties, and processes for solar cell encapsulants

The results of an investigation of solar module encapsulation systems applicable to the Low-Cost Solar Array Project 1986 cost and performance goals are presented. Six basic construction elements were identified and their specific uses in module construction defined. A uniform coating basis was established for each element. The survey results were also useful in revealing price ranges for classes of materials and estimating the cost allocation for each element within the encapsulating cost goal. The six construction elements were considered to be substrates, superstrates, pottants, adhesives, outer covers and back covers

Is there really a value in entrepreneurship education?

This paper considers whether entrepreneurship education has a value outside of the education institutions in which it takes place. The paper takes an indirect form of enquiry and argues that entrepreneurship education is driven by three factors; the growing emphasis on supply side policy interventions in the economy; the emphasis placed on the agency of management in the growing literature on globalisation and international reforms to public sector organisations. The paper concludes that there is a tension between the activity as descriptive and the activity as promotion and until this tension is resolved it is unlikely that there will be clarity about the value of this form of education

The Economic Consequences of Widowhood

We analyzed the economic consequences of a husband’s death using events that occurred between the first two waves of the HRS and AHEAD studies. We compared poverty transitions against published results from Social Security’s Retirement History Survey of the 1970s. Widowhood remains an important risk factor for transition into poverty, although somewhat less so than twenty years ago. Women over age 65 (AHEAD) are less likely to experience severe economic changes than women under age 61 (HRS). Several factors account for the age differences: the declining importance of husband’s earnings with age, the rising importance of Social Security benefits, and the occasionally large out-of-pocket medical expenses associated with husband’s death before Medicare eligibility. The greater economic impact of widowhood at younger ages is consistent with our cross-section evidence that poverty rates rise with duration of widowhood but are only weakly associated with age.

The role of the Initial Teacher Training Coordinator in the school based element of partnership: to what extent does the Co-ordinator undertake supervision of aspects of quality assurance?

Over the last 14 years, Universities and colleges have organised school placements and award qualifications whilst teachers, acting as mentors take the lead in guiding, supervising and assessing students on lengthy teaching placements. Partnership developed quickly in response to legislation and Sheffield Hallam University was among the first of the Universities to 'sign up' to the new partnership model in 1992. The Partnership Survey 2006 reported on in this paper has focussed on the Senior Liaison Tutor with a view to finding out their views on their role, and perceived contributions to the quality assurance of the partnership. The survey focussed on some of the key issues identified in previous studies and meetings of the Partnership Management Board.</p