Shields

Abstract: This book is translated from German. The development potential of the mechanised shield tunnelling method is far greater than that of the shotcrete method and other traditional tunnelling machines because it is a safer, more effective method of tunnel construction. This book considers the planning of the construction method and design of the machine in harmony with the geological and hydrological conditions, settlement requirements and safety considerations. The technological developments in Germany and world-wide are presented. The book includes chapters on tunnel lining, tailskin seals, grouting and injection procedures, open-faced shields, compressed air shields, slurry shields, earth pressure balance shields, combined shields and special configuration shields and special construction methods.

Abstract: An analysis of the shielding effectiveness of braidedwire shields is made using the parameters of the woven wire and the theory of electromagnetic coupling through small irises. The coupling through the rhombic-shaped holes in the braid is approximated by using the electric and magnetic polarizabilities of elliptical holes of the same width and length as the rhombus. The analysis develops the transfer impedance and the mutual capacitance of the shield. The transfer impedance is calculated and plotted for shields of different optical coverages. The variation of mutual capacitance and mutual inductance with the weave angle of the braid are examined.

Abstract: The development of transparent flexible dust shields using both single- and three-phase electrodynamic shields is reported here for possible application on Mars and Earth to minimize obscuration of solar panels from the deposition of dust. The electrodynamic screens (EDS) are made of transparent plastic sheets, such as polyethylene terephthalate (PET) for its UV radiation resistance, and a set of parallel conducting electrodes made of transparent indium tin oxide (ITO) embedded under a thin transparent film. The basic principle of EDS operation, a simplified mathematical model of particle trajectories, the experimental setup used for testing the screens, and their dust removal efficiencies (DRE) are described. Results of our measurements on dust removal efficiency of EDS as a function of the particle size and electrostatic charge distributions of Mars simulant dust are reported. The results show that the EDS technology has a strong potential for protecting solar panels against dust hazards with DRE higher...

Abstract: High-permeability magnetic shields generate magnetic field noise that can limit the sensitivity of modern precision measurements. We show that calculations based on the fluctuation-dissipation theorem allow quantitative evaluation of magnetic field noise, either from current or magnetization fluctuations, inside enclosures made of high-permeability materials. Explicit analytical formulas for the noise are derived for a few axially symmetric geometries, which are compared with results of numerical finite element analysis. Comparison is made between noises caused by current and magnetization fluctuations inside a high-permeability shield and also between current-fluctuation-induced noises inside magnetic and non-magnetic conducting shells. A simple model is suggested to predict power-law decay of noise spectra beyond quasi-static regime. Our results can be used to assess noise from existing shields and to guide design of new shields for precision measurements.