Laboratory investigation of electric charging of dust particles by electrons, ions, and UV radiation

In many cosmic environments electric charging of dust particles occurs by electrons, ions, and UV radiation. In case of interstellar dust particles the value of their electric charge can have, for instance, very important consequences for their destruction rate in supernova remnant's shock waves and can globally influence the overall life cycle of dust particles in galaxies. For experimental simulation of charging processes a vacuum chamber was used in which the particles fall through an electron or ion beam of energies up to 10 KeV. The aim of the experiments was to attain maximum charge of dust particles. Furthermore the influence of the rest gas was also determined because electrons and ions produced by collisional ionization of the rest gas can result in significant effects. For measurement particles from 1 to 100 microns from glass, carbon, Al, Fe, MgO, and very loosely bound conglomerates of Al2O3 were used

Bifurcation of standing waves into a pair of oppositely traveling waves with oscillating amplitudes caused by a three-mode interaction

A novel flow state consisting of two oppositely travelling waves (TWs) with oscillating amplitudes has been found in the counterrotating Taylor-Couette system by full numerical simulations. This structure bifurcates out of axially standing waves that are nonlinear superpositions of left and right handed spiral vortex waves with equal time-independent amplitudes. Beyond a critical driving the two spiral TW modes start to oscillate in counterphase due to a Hopf bifurcation. The trigger for this bifurcation is provided by a nonlinearly excited mode of different symmetry than the spiral TWs. A three-mode coupled amplitude equation model is presented that captures this bifurcation scenario. The mode-coupling between two symmetry degenerate critical modes and a nonlinearly excited one that is contained in the model can be expected to occur in other structure forming systems as well.Comment: 4 pages, 5 figure

Competition between Traveling Fluid Waves of Left and Right Spiral Vortices and Their Different Amplitude Combinations

Stability, bifurcation properties, and the spatiotemporal behavior of different nonlinear combination structures of spiral vortices in the counter rotating Taylor-Couette system are investigated by full numerical simulations and by coupled amplitude equation approximations. Stable cross-spiral structures with continuously varying content of left and right spiral modes are found. They provide a stability transferring connection between the initially stable, axially counter propagating wave states of pure spirals and the axially standing waves of so-called ribbons that become stable slightly further away from onset of vortex flow.Comment: 4 pages, 5 figure

Analysis of some global optimization algorithms for space trajectory design

In this paper, we analyze the performance of some global search algorithms on a number of space trajectory design problems. A rigorous testing procedure is introduced to measure the ability of an algorithm to identify the set of ²-optimal solutions. From the analysis of the test results, a novel algorithm is derived. The development of the novel algorithm starts from the redefinition of some evolutionary heuristics in the form of a discrete dynamical system. The convergence properties of this discrete dynamical system are used to derive a hybrid evolutionary algorithm that displays very good performance on the particular class of problems presented in this paper

Effect of Surfactant upon Capillary Adhesion in Four-phase Systems

Liquid bridges of aqueous sodium dodecyl sulphate solutions with different concentration between polytetrafluoro ethylene and pyrex glass surface have been experimentally investigated. The drop distribution isotherms are of the same type, their general shape being independent of the surfactant concentration but the characteristic points as the critical drop mass for total adherence and the constant drop mass corresponding to the steady state strongly depend on the surfactant concentration. The stability of the bridges as well as the formation of satellite droplets after breakdown of the bridge have been interpreted in terms of capillary waves. A simple energetic model consideration is proposed to explain effects caused by hysteresis

Spiral vortices traveling between two rotating defects in the Taylor-Couette system

Numerical calculations of vortex flows in Taylor-Couette systems with counter rotating cylinders are presented. The full, time dependent Navier-Stokes equations are solved with a combination of a finite difference and a Galerkin method. Annular gaps of radius ratio $\eta=0.5$ and of several heights are simulated. They are closed by nonrotating lids that produce localized Ekman vortices in their vicinity and that prevent axial phase propagation of spiral vortices. Existence and spatio temporal properties of rotating defects, of modulated Ekman vortices, and of the spiral vortex structures in the bulk are elucidated in quantitative detail.Comment: 9 pages, 9 figure

Social Cost Benefit Analysis of the no recourse to public funds (NRPF) policy in London

This report estimates the monetised social and economic gains (benefits) of removing of the No Recourse to Public Funds (NRPF) condition for certain household in England. It compares this to the costs of allowing them to be able to apply for welfare benefits and various public services paid for from public funds. This is in the form of a Social Cost Benefit Analysis and was prepared as an independent analysis for the Greater London Authority. The households in scope are households and families with visas statuses including the right to work, some of whom are on visa routes that could lead to long-term settlement in the UK. These includes holders of Tier 1, 2 or 5 visas who come to the UK to work and their dependents; those who are in the UK because of family links; dependents or others who are linked to the primary visa holder and those estimated to come via the Hong Kong British National Overseas scheme. The report estimates that there are approximately 362,000 households, including 106,000 households with children, would potentially be affected by lifting the NRPF condition. Access to public funds would be restricted by existing qualifying conditions limiting access to welfare benefits and other services to households in need of this public assistance. It found that, over ten years, removing the NRPF condition just for households with children and other vulnerable individuals would result in a net gain of £872 million. Removing the condition for all those on these visas would result in a £428 million net gain