| 1 | The Sensitivity to Axial Alignment of a Flow Driven by a Travelling Magnetic Field显示文摘The present study,both experimentally and by numerical simulation,concerns the sensitivity of a flow that is driven by a travelling magnetic field(TMF)with respect to a stepwise applied mismatch between the axes of the TMF and of the cylindrical liquid metal column.The TMF is generated by six equidistantly arranged cylindrical coils powered with an AC current having a phase shift of 60℃between them.Because the flow induced by a TMF is basically of a toms type,vertical velocity components are representative for the motion in the meridional plane.Ultrasound Doppler Velocimetry(UDV)was applied to acquire the velocity component along the beam axis in the centre of the liquid metal column and at various azimuthal positions for a fixed radial coordinate.The measurements are compared to the flow data gained by large eddy simulations.Computations were based on the usual approximations to simplify the magnetohydrodynamic equations,which are low frequency and low induction,and on an analytical expression for the Lorentz force considering the shift between the fluid volume and the field.The results show that even a small shift between the axes may result in a distinct three-dimensional constituent of the flow structure which changes completely the usually assumed axisymmetric toms-type flow. | PAL Josef CRAMER Andreas GERBETH Gunter KOAL Kristina TSCHISGALE Silvio STILLER Jrg | 2012 | Journal of Iron and Steel Research(International)2012，19，S1： | 0 |
| 2 | Role of forests in headwater control with changing environment and society显示文摘Forest practices in headwater catchments are related to environmental and social contexts.The aim of this study is to analyse the changing protective functions of forests in the upper plain of the Jizera Mts.(North Bohemia,Czech Republic)since the second half of the 19th century.With time,forests have gradually changed from native stands to spruce plantations(Picea abies),introducing exotic conifers(more resistant to air pollution),and,recently,back to more diverse mixed stands.The priority in pro-tective forest functions there shifted from flood protection to integrated control of water resources(quantity and quality).In the 1980s,forest-water interactions were degraded by consequences of extreme acid atmospheric deposition,forest die-back,and extensive clear-cut.In the Jizerka catchment,first signs of recovery were observed in the early 1990s.but.stream waters there are still affected by prolonged acidification.While reconstruction of stream water chemistry at Jizerka follows the drop of the acid deposition in some 5 years,the revival of stream biota takes 10-15 years.In 2071-2100,the pro-jected climate change shows rising annual air temperatures by 3.0-4.6℃,decreasing water yield by 65-123 mm,60%drop in'minimum residual discharge',and 20-30%rise in peak-flows.However,these projected environmental changes cannot substantially decline the high potential in water resource recharge,or,start reverse processes in recent recovery from acidification and radically affect the exis-tence of planned mixed forests in the upper plain of the Jizera Mts. | Josef Krecek Jana Nováková Ladislav Palán Eva Pazourková Evzen Stuchlík | 2021 | International Soil and Water Conservation Research2021，9，1： | 0 |
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