Morphing surfaces for the control of boundary layer transition

A structure configured to modify its surface morphology between a smooth state and a rough state in response to an applied stress. In demonstrated examples, a soft (PDMS) substrate is produced, and is pre-strained. A relatively stiff overlayer of a metal, such as chromium and gold, is applied to the substrate. When the pre-strained substrate is allowed to relax, the free surface of the stiff overlayer is forced to become distorted, yielding a free surface having a roughness of less than 1 millimeter. Repeated application and removal of the applied stress has been shown to yield reproducible changes in the morphology of the free surface. An application of such morphing free surface is to control a boundary layer transition of an aerodynamic fluid flowing over the surface

Germany’s Current Account and Trade Surpluses A Technical Debate Enters the Geopolitical Limelight. Bertelsmann Stiftung GED Study April 2018

During the past decade, macroeconomic imbalances – typified by countries’ surplus or deficit of exports, currency, or capital – have moved to the fore of international economic policy debates. Global events and developments, such as China’s integration into the world economy, the 2008 financial crisis, and the Eurozone crisis, have created, and in some cases, compounded longstanding trade and investment asymmetries around the world. These imbalances have no single cause, but are fostered and magnified by the competitiveness of a country’s industries, domestic demand, corporate investment decisions, and tax and monetary policy, among other factors. In recent years, the widening gaps in countries’ trade relationships have become highly politicized, prompting policymakers to respond with measures ranging from formalized monitoring to punitive tariffs

The uses of mercury equipment and products in Irish healthcare

Mercury is a naturally occurring metal, one of the most toxic metals within the food chain and has a number of uses in the Irish health care sector. This paper reports on a mercury survey in Ireland with the purpose to present a picture of mercury use in health settings. The findings show 50% of health settings free of all mercury medical equipment. Mercury spills occur within 30% of health settings, with no training provided in handling mercury equipment, in the management of mercury spills and only 10% of health services have mercury clean up kits. With 50% of mercury waste disposed inappropriately, a number of recommendations are advanced for reducing the amount of mercury in the health settings alongside awareness and education for health professionals

Morphing surfaces for the control of boundary layer transition

A structure configured to modify its surface morphology between a smooth state and a rough state in response to an applied stress. In demonstrated examples, a soft (PDMS) substrate is produced, and is pre-strained. A relatively stiff overlayer of a metal, such as chromium and gold, is applied to the substrate. When the pre-strained substrate is allowed to relax, the free surface of the stiff overlayer is forced to become distorted, yielding a free surface having a roughness of less than 1 millimeter. Repeated application and removal of the applied stress has been shown to yield reproducible changes in the morphology of the free surface. An application of such morphing free surface is to control a boundary layer transition of an aerodynamic fluid flowing over the surface

Critical-layer structures and mechanisms in elastoinertial turbulence

Simulations of elastoinertial turbulence (EIT) of a polymer solution at low Reynolds number are shown to display localized polymer stretch fluctuations. These are very similar to structures arising from linear stability (Tollmien-Schlichting (TS) modes) and resolvent analyses: i.e., critical-layer structures localized where the mean fluid velocity equals the wavespeed. Computation of self-sustained nonlinear TS waves reveals that the critical layer exhibits stagnation points that generate sheets of large polymer stretch. These kinematics may be the genesis of similar structures in EIT.Comment: 5 pages, 4 figures; Accepted in Physical Review Letter

Axial Couplings on the World-Line

We construct a world-line representation for the fermionic one-loop effective action with axial and also vector, scalar, and pseudo-scalar couplings. We use this expression to compute a few selected scattering amplitudes. These allow us to verify that our method yields the same results as standard field theory. In particular, we are able to reproduce the chiral anomaly. Our starting point is the second-order formulation for the Dirac fermion. We translate the second order expressions into a world-line action.Comment: 12 pages, LaTeX 2e with array and epsf packages, Postscript figures. Submitted to Phys. Lett. B. Minor corrections, fixed a number of typo