Ka and Q band propagation experiments in Toulouse using ASTRA 3B and ALPHASAT satellites

From January 2008 to March 2011, ONERA operated in Toulouse, France, a beacon receiver able to collect the 19.7‐GHz beacon signal of the HotBird 6 satellite. In March 2011, the radio frequency chain was modified to be able to receive the 20.2‐GHz ASTRA 3B beacon to benefit from a higher Equivalent Isotropically Radiated Power of the satellite. Since June 2015, a second beacon receiver has been installed and is able to record the 39.4‐GHz beacon signal of the Alphasat satellite. The objective of this paper is to present the results of the first 2 years of measurements (June 2015 to May 2017) of the Q‐band Alphasat propagation experiment in Toulouse, as well as concurrent measurements collected at Ka‐band with ASTRA 3B. First of all, the propagation experiments are briefly described. Second, the results of the statistical analysis are highlighted. Finally, a deep analysis of the performances of the 2 frequency scaling prediction methods recommended in ITU‐R P.618‐13 is performed.     

Power‐Law Fluid Flow Over a Sphere: Average Shear Rate and Drag Coefficient

Based on the consideration of the rate of mechanical energy dissipation, an expression for the average shear rate for a sphere falling in a power‐law fluid in the creeping flow regime has been deduced. The average shear rate in a power‐law fluid (n<1) appears to be higher than that in an equivalent Newtonian fluid. This in turn has been combined with the numerical predictions of drag coefficient (up to Reynolds number of 100) of a sphere to develop a generalized drag correlation for power‐law liquids encompassing both n > 1 and n < 1 which appears to apply up to much higher values of the Reynolds number. The available experimental data have been used to demonstrate the reliability and accuracy of the new correlation for shearthinning liquids. Also, in the limit of n = 1, this expression reproduces the standard drag curve with a very high accuracy.     

Increasing the Efficiency of Organic Dye‐Sensitized Solar Cells over 10.3% Using Locally Ordered Inverse Opal Nanostructures in the Photoelectrode

3D inverse opal (3D‐IO) oxides are very appealing nanostructures to be integrated into the photoelectrodes of dye‐sensitized solar cells (DSSCs). Due to their periodic interconnected pore network with a high pore volume fraction, they facilitate electrolyte infiltration and enhance light scattering. Nonetheless, preparing 3D‐IO structures directly on nonflat DSSC electrodes is challenging. Herein, 3D‐IO TiO₂ structures are prepared by templating with self‐assembled polymethyl methacrylate spheres on glass substrates, impregnation with a mixed TiO₂:SiO₂ precursor and calcination. The specific surface increases from 20.9 to 30.7 m² g^?1 after SiO₂ removal via etching, which leads to the formation of mesopores. The obtained nanostructures are scraped from the substrate, processed as a paste, and deposited on photoelectrodes containing a mesoporous TiO₂ layer. This procedure maintains locally the 3D‐IO order. When sensitized with the novel benzothiadiazole dye YKP‐88, DSSCs containing the modified photoelectrodes exhibit an efficiency of 10.35% versus 9.26% for the same devices with conventional photoelectrodes. Similarly, using the ruthenium dye N719 as sensitizer an efficiency increase from 5.31% to 6.23% is obtained. These improvements originate mainly from an increase in the photocurrent density, which is attributed to an enhanced dye loading obtained with the mesoporous 3D‐IO structures due to SiO₂ removal.     

Recycling zinc oxide varistor blocks for electro‐active silicone composites

The recycling process toward the elimination of varistor wastes into new electro‐active silicon composites has been investigated. We studied the dependence of the E‐J characteristics on the aggregate content in the polymer matrix. Formulations with 40 vol.% metal oxide varistor aggregates in the 100‐200 μm range exhibit reliable nonlinear behavior with a switching voltage of 280±30 V/mm. The breakdown voltage of the composite decreases as both filler's diameter and filler's volume fraction increases in the 550‐220 V/mm and 440‐280 V/mm range, respectively. This paves the way for the valorization of varistors based zinc oxide (ZnO) ceramics.     

Role of shear stress on composition, diversity and dynamics of biofilm bacterial communities

This article evaluates the effect of shear stress on the composition of biofilm bacterial communities. For the first time, a Conical Couette-Taylor Reactor (CCTR) was used to develop biofilms at varying shear stresses (from 0.055 to 0.27 Pa) and provided a useful model for studying the effect of hydrodynamics on biofilms. The composition, diversity and dynamics of biofilm bacterial communities were analysed using the PCR-SSCP fingerprint method. Results clearly demonstrate a link between shear stress and composition of the microbial communities. High shear stresses decrease biofilm diversity and the analysis of biofilm community dynamics suggests that shear stress would slow down biofilm maturation and tend to maintain a young biofilm.     

Selection of an adsorbent for lead removal from drinking water by a point-of-use treatment device

The removal of lead from drinking water was investigated to develop a point-of-use water filter that could meet the regulation imposed by the new European Directive 98-83 lowering lead concentration in drinking water below 10 μg L⁻¹. The objective of this research was to assess the potential of different adsorbents (zeolites, resins, activated carbon, manganese oxides, cellulose powder) to remove lead from tap water with a very short contact time. To begin, the repartition of the lead species in a tap water and a mineral water was computed with the computer model CHESS. It showed that in bicarbonated waters lead is mainly under lead carbonate form, either in the aqueous or in the mineral phase. Batch experiments were then conducted to measure the equilibrium adsorption isotherms of the adsorbents. Then, for five of them, dynamic experiments in micro-columns were carried out to assess the outlet lead concentration level. Three adsorbents gave rise to a leakage concentration lower than 10 μg L⁻¹ and were then selected for prototypes experiments: chabasite, an activated carbon coated with a synthetic zeolite and a natural manganese oxide. The proposed method clearly showed that the measurement of equilibrium isotherms is not sufficient to predict the effectiveness of an adsorbent, and must be coupled with dynamic experiments.     

A 65nm CMOS Ramp Generator Design and its Application Towards a BIST Implementation of the Reduced-Code Static Linearity Test Technique for Pipeline ADCs

This work presents an efficient on-chip ramp generator targeting to facilitate the deployment of Built-In Self-Test (BIST) techniques for ADC static linearity characterization. The proposed ramp generator is based on a fully-differential switched-capacitor integrator that is conveniently modified to produce a very small integration gain, such that the ramp step size is a small fraction of the LSB of the target ADC. The proposed ramp generator is employed in a servo-loop configuration to implement a BIST version of the reduced-code linearity test technique for pipeline ADCs, which drastically reduces the volume of test data and, thereby, the test time, as compared to the standard test based on a histogram. The demonstration of the pipeline ADC BIST is carried out based on a mixture of transistor-level and behavioral-level simulations that employ actual production test data.     

An activity, stability and selectivity comparison of propioin synthesis by thiamine diphosphate-dependent enzymes in a solid/gas bioreactor

Enzymatic carboligation in a solid/gas bioreactor represents a new challenge in biotechnology. In this paper, the continuous gas-phase production of propioin from two propanal molecules by using thiamine diphosphate-dependent enzymes was studied. Two enzymes were used, namely benzaldehyde lyase (BAL) from Pseudomonas fluorescens and benzoylformate decarboxylase (BFD) from Pseudomonas putida. The enzymes are homologous and catalyze carboligase and carbolyase reactions in which no external cofactor regeneration is needed. The influence of water and substrate activity on the initial reaction rate and biocatalyst stability was investigated. An increase in water activity raised the initial reaction rates to the maximal values of 250 and 80 U g(-1) for BAL and BFD, respectively. The half-life showed the same trend with maximal values of 50 and 78 min for BAL and BFD, respectively. The increase in the half-life by increasing water activity was unexpected. It was also observed that BFD is more stable than BAL in the presence of the substrate propanal. Both enzymes showed substrate inhibition in the kinetic studies, and BAL was also deactivated during the reaction. Unexpectedly, the stereoselectivity of both enzymes (ee of 19 % for BAL and racemic mixture for BFD) was significantly impaired in the gas phase compared to the liquid phase.     

Twelve years of rain attenuation statistics of Earth–space propagation experiment at Ka band in Toulouse

Since 2009, ONERA has been running Ka band propagation experiments in Toulouse (France, latitude 43.57°N, longitude 1.47°E). A rain gauge was also deployed on site to collect rainfall rate measurements concurrently to beacon data. Since April 2011, the beacon receiver has been recording the 20.2 GHz (vertical polarisation) Astra 3B beacon signal along a slant path of 35.1° of elevation angle. All years of the experiment had excellent data availability, hence giving 12 years of data at Ka band. First, the propagation experiment and the data processing methodology are described. Second, a statistical analysis of rain attenuation and rainfall rate is conducted. Comparisons are then performed with the prediction methods of Recommendations ITU-R P.837-7 (rainfall rate), P.618-13 (rain attenuation) and P.678-3 (variability of propagation phenomena).