Broadband CDMA for personal communications systems

Multipath propagation in a broadband CDMA environment is described. A propagation model for broadband spread-spectrum signals is presented. Experimental results relating to the sharing of the band by fixed service microwave users and mobile personal communications network (PCN) users are discussed. Field tests indicate that PCN systems can provide high-quality communications when sharing the spectrum with fixed-service microwave systems in suburban and urban areas     

Photovoltaic collectors efficiency according to their integration in buildings

A model for building integrated photovoltaic systems has been developed and implemented in a dynamic simulation tool. This tool takes into account the thermal interactions between the PV collector and the building. The influence of the type of integration upon the PV collector efficiency has been evaluated and hybrid PV/air collectors have been studied. An overall efficiency is defined, including the production of electricity and heat. A case study has been performed on two different typical buildings. In the case of a multi-crystalline silicon PV collector integrated on the roof of a single family house located in Paris, the efficiency of unventilated PV modules fixed on the roof is 14%. If the PV collector is used to preheat the ventilation air, the efficiency reaches 20%. A proper building integration also improves the environmental balance of PV technologies over their life cycle.     

Controlling the losing probability in a monotone game

We deal with a complex game between Alice and Bob where each contender’s probability of victory grows monotonically by unknown amounts with the resources employed. For a fixed effort on Alice’s part, Bob increases his resources on the basis of the results for each round (victory, tie or defeat) with the aim of reducing the probability of defeat to below a given threshold. We read this goal in terms of computing a confidence interval for the probability of losing and realize that the moves in some contests may bring in an indeterminacy trap: in certain games Bob cannot simultaneously have both a low probability-of-defeat measure and a narrow confidence interval. We use the inferential mechanism called twisting argument to compute the above interval on the basis of two joint statistics. Careful use of such statistics allows us to avoid indeterminacy.     

Measuring interdiffusion at an interface between two elastomers with tapping-mode and contact-resonance atomic force microscopy imaging

Despite the common use of tapping-mode atomic force microscopy to image composites or polymer blends, very few studies have focused on the measurement of the interdiffusion at an interface between two polymers in contact. In this study, we show how to assess the interphase between two polymers with two methods. First, stable and robust tapping conditions are established, and the problem of the phase contrast is discussed. Second, a contact-resonance method is presented: the tip in contact with the sample is electrostatically excited at its resonance frequency by a self-controlled oscillator. The gain and frequency images allow us to measure the interdiffusion width. Both methods (using high and weak mechanical solicitation) give the same assessment of the interdiffusion width. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

The influence of magnetron sputtered silver and titanium coatings on the compaction and properties of surface modified PM Ti-48Al powders

Thin layers of silver and titanium were deposited onto commercial Ti–₄₈Al particles by magnetron sputtering prior to their consolidation by hot isostatic pressing and subsequent heat treatment. Based on picnometry and electron probe microanalysis results, average values of 1.5 and 2.5 at.%, respectively, were obtained for the silver and titanium contents in the coated particles. The surface modified Ti–₄₈Al particles exhibited improved sintering ability than the unmodified ones. The consolidated samples have duplex microstructures formed by γ-TiAl and γ-TiAl + α₂-Ti₃Al grains. Ag-rich nanoprecipitates were detected in the microstructure of the compacted Ti-₄₈Al + Ag sample. The coatings are no longer visible at the grains boundaries after a subsequent homogenization heat treatment at 1200°C. The highest values of hardness and Young’s modulus were obtained for the Ti–₄₈Al + Ag sample, associated with a higher density and a lower percentage of pores.     

Farbmeßgeräte für transparente Flüssigkeiten sichern die Qualität in der chemischen Industrie – Qualitätskontrolle an transparenten Flüssigkeiten

Colour Measuring Instruments for Transparent Liquids Safeguard the Quality in the Chemical Industry – Quality Control of Transparent Liquids In many areas of the chemical industry a complete product specification comprises – besides various other parameters – the colour characteristics as well. The colour of transparent liquids is still frequently determined by visual comparison of the product with e.g. iodine, Hazen- or Gardner colour standard solutions or appropriate colourfilter discs. In 1989 a new DIN 53995 standard for instrumental colour assessment of transparent liquids was introduced to replace the error-prone, subjective methods of visual comparisons. Dr. Lange GmbH, Düsseldorf, has developed the LICO 200 spectrophotometer under consideration of the new DIN 53995 for objective colour assessment in compliance with the iodine, Hazen and Gardner colour scales.     

Coupled Physical and Numerical Simulation to Optimize Thermo‐mechanical Metal Forming Processes

The numeric simulation of thermo‐mechanical hot forming processes and the modelling of the structure development and the mechanical properties of complex metallic materials serve for both the optimization of forming processes and the increase of process reliability. To meet close process windows, predictions of the formability of the material as function of the process conditions and material history are required as well. Lifetime evaluation of the tools is made possible from coupled computation of workpiece and tool loads. Material and damage models in use must be adapted on the basis of laboratory experiments and advanced analysis methods.