Power spectrum of microbends in monomode optical fibres

A new model is proposed for the power spectrum of microbends in monomode optical fibres. This model is based on the idea that microbends are extended rather than point, as has been previously assumed. By fitting our model to the experimental data we obtain values for the wavelength and correlation length of the disturbance causing the microbends.     

Shrinkage Reduction in Silica-based Refractory Cores Infiltrated with Boehmite

Infiltration of silica-based refractory cores with colloidal boehmite slurry has the effect of greatly reducing sintering shrinkage, as required for precision casting. Only 300 ppm of equivalent alumina is sufficient to decrease the shrinkage from RT to 1600°C more than three-fold. Microstructural observations and XPS measures show that the silica grains are homogeneously coated with a reaction film which hinders viscous flow.     

Sequential flow process for the controlled polymerisation and thermolysis of RAFT-synthesised polymers

The RAFT (Reversible Addition-Fragmentation Chain Transfer) process greatly enhances the control over radical polymerisations, while leaving behind a thiocarbonylthio end-group. Thermolysis presents a convenient and efficient way of removing the thiocarbonylthio end-group from RAFT polymers, without the use of additional reagents. This paper describes a simple two-step flow process for the synthesis of RAFT polymers followed by the subsequent removal of the RAFT end-group via thermolysis, without the need for isolating intermediates. A range of different polymers based on styrene, acrylates, methacrylates and acrylamides were synthesised with different RAFT agents and successfully tested for thermolysis at temperatures between 220 and 250 °C in a stainless steel tube flow reactor, resulting in complete removal of thiocarbonylthio end-groups.     

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Passive optical local networks for telephony applications and beyond

A new digital telephone system is described using a passive optical network. Downstream transmission is broadcast and optical time-division, multiple-access (OTDMA) is used in the upstream path. The principle advantage of this approach is that exchange resources and fibres are shared between a large number of customers     

INTEGRATED OUTCROP ANALOGUE STUDIES FOR TRIASSIC ALLUVIAL RESERVOIRS: EXAMPLES FROM SOUTHERN GERMANY

Outcrops of Upper Triassic (Keuper) alluvial sandstones in South Germany may provide analogues for recently -discovered hydrocarbon reservoirs in the North Sea Triassic. Using an integrated approach, reservoir heterogeneities in the outcropping sandstones may be characterized by means of: (1) sequence stratigraphy (including facies and architectural element analysis aided by georadar profiling, and an identification of the hierarchy of sedimentary cycles); and (2) petrophysics (gamma-ray logging, and porosity and permeability measurements). Primary depositional facies and the stacking patterns of different fluvial cycles within larger-scale sedimentary cycles play a dominant role in determining the fluid-flow behaviour of the sandstones.     

Development of superconducting and cryogenic technology in the Institute for Technical Physics (ITP) of the Research Center Karlsruhe

Since the early 1970s the Institute for Technical Physics of the Research Center Karlsruhe has been involved in the development of superconductivity for research and industrial applications. A broad program with a focus on the superconducting magnet technology was established to include large magnets for nuclear fusion, high-field magnets for nuclear magnetic resonance spectrometers, ore separation and energy storage magnets. Research and development work was performed in collaborative projects with other national as well as international institutions and industry. The success of these projects has been supported by a broad foundation of engineering science in superconductor development, electrical and cryogenic engineering. Several well known test facilities like TOSKA, STAR, HOMER, MTA along with well equipped laboratories for conductor development, materials at cryogenic temperatures, cryogenic high-voltage engineering have made substantial contributions to in-house, national and international projects. A strong cryogenic infrastructure with two refrigerators and sophisticated cooling circuits from about 4.5 K down to 1.8 K assure the reliable operation of these large facilities. Last but not least, cryogenic research, including vacuum pumps for International Thermonuclear Experimental Reactor, improvements in thermal insulation, cryogenic instrumentation and small on board refrigerators has supported progress in this field. High-temperature superconductivity projects for low AC loss conductors, a 70 kA current lead and a fault current limiter are currently in progress.