On piecewise smoothness of conjugacy of class P circle homeomorphisms to diffeomorphisms and rotations

We give a characterization of piecewise C ¹ class P-homeomorphism f of the circle with irrational rotation number and finitely many break points which is piecewise C ¹ conjugate to a C ¹-diffeomorphism. The following properties are equivalent:

?(i)?f is conjugate to a C ¹-diffeomorphism of the circle by a piecewise C ¹-homeomorphism. (ii)?The product of jumps of f in the break points contained in a same orbit is trivial. (iii)?f is conjugate to a C ¹-diffeomorphism of the circle by a piecewise linear (PL)-homeomorphism or a piecewise quadratic homeomorphism.

For a PL-homeomorphism f having the property (ii): f is conjugate to a rotation either by a PL-homeomorphism or by a piecewise analytic homeomorphism.     

H2 sensors based on WO3 thin films activated by platinum nanoparticles synthesized by electroless process

Platinum (Pt) nanoparticles were successfully synthesized on tungsten oxide (WO₃) thin films by electroless process without any further post-treatment. The prepared Pt nanoparticles were characterized by X-ray diffraction, X-ray photoelectron spectroscopy and field-emission scanning electron microscopy. Gas sensors based on the Pt–WO₃ films were found to provide repeatable and significant responses to ppm-level H₂. The size of Pt nanoparticles increases with the deposition time and has improved the sensing characteristics of the sensors. The work in this paper paves a facile way to the fabrication of Pt nanoparticles on metal oxide surface at a low temperature (68 °C).     

Sol–Gel Assisted Preparation of Chromia–Silica Catalysts for Non-Oxidative Dehydrogenation of Propane

Preparation of continuous silica gel in the presence of dissolved Cr(NO₃)₃ leads to a hard high surface area (710 m²/g) microporous xerogel. Formation of the gel in the pore structure of mesoporous Pore-Expanded MCM-41 (PE-MCM-41) and macroporous commercial Cab–O–Sil silica results in retention of the mesoporous structure in the case of PE-MCM-41, and the formation of a powder with a broad pore size distribution in the case of Cab–O–Sil silica. Comparison of the catalytic activities in non-oxidative dehydrogenation of propane revealed a linear correlation of the initial conversion with the surface area for all three samples. The sample prepared from PE-MCM-41 through a sol–gel assisted procedure was the most active, particularly with respect to the catalysts prepared by simple wet impregnation with chromium nitrate.     

Synthesis of onion-like mesoporous silica from sodium silicate in the presence of α,ω-diamine surfactant

Mesoporous silicas with vesicular and onion-like morphologies were assembled through hydrogen-bonding pathway from sodium silicate as silica source and electrically neutral α,ω-diamine, Jeffamine D2000 surfactant (H₂NCH(CH₃)CH₂[OCH₂CH(CH₃)]₃₃NH₂) as template in aqueous media at different synthesis temperatures (25, 60 and 100 °C). Assembling the material at 100 °C afforded onion-like core shell mesoporous silica, while at relatively lower temperature, e.g. 25 and 60 °C, multilamellar vesicles were obtained. Mesoporous silica with onion-like morphology was also obtained by a two-step synthesis involving an aging period of 20 h at room temperature followed by a hydrothermal stage (1–12 h) at 100 °C. The heavily cross-linked (Q⁴/Q³ ratio of 4.43) onion-like mesophase silica exhibited high hydrothermal stability. The BET surface area, pore volume and KJS (Kruk-Jaroniec-Sayari) pore diameter of the onion-like mesoporous silica were found to be 464 m² g⁻¹, 1.16 m³ g⁻¹ and 7.2 nm, respectively.     

Regeneration of a solid waste from an edible oil refinery

This work presents a valorization of a solid waste originating from an edible oil refinery called spent bleaching earth (SBE). The SBE material is first impregnated with an ammonium chloride solution (3 M), then treated directly in furnace at 400 °C during an hour followed by a washing in the cold by HCl 1 M. To elucidate the changes in its crystalline structure, induced by the regeneration method, the obtained material (RSBE) is characterized by several physicochemical methods (X-ray diffraction, FTIR, thermal analysis, BET and SEM). The characterization results show that the heat treatment in furnace and the chemical treatment (decomposition of NH₄Cl) don’t affect the structure of montmorillonite of regenerated material (RSBE). The study of porous texture by the nitrogen adsorption technique at −196 °C shows that the specific surface area S_BET and the pore volume increased in the RSBE material compared to those of virgin bleaching earth VBE (unused) and their values are respectively of 145.68 against 115.5 m² g⁻¹ and of 0.287 against 0.234 cm³ g⁻¹. Calculations by the adsorption equations using BJH method, applied to both materials, show that the treatment generate an increase in the micropores in the RSBE material. We belonged the values of the micropores area of S_mic = 41.98 cm² g⁻¹ and of V_mic = 0.074 cm³ g⁻¹ for the volume.     

Rhodium Complexed C2‐PAMAM Dendrimers Supported on Large Pore Davisil Silica as Catalysts for the Hydroformylation of Olefins

Polyamidoamine (PAMAM) dendrimers up to the third generation were grown for the first time on the surface of a large‐pore (18 nm) Davisil silica support. The supported dendrimers of generations 0, 1, 2 and 3 were phosphinomethylated and complexed with rhodium. All the generations were found to be very active for the hydroformylation of olefins. The hydroformylation of 1‐octene was accomplished with a turnover frequency of 1700 h⁻¹ at 70 °C. The G(1) material was found to be the most active when the different generations were compared at 50% conversion at 70 °C     

A new position regulation strategy for VTOL UAVs using IMU and GPS measurements

We propose a new position regulation strategy for VTOL-UAVs using IMU and GPS measurements. Since there is no sensor that measures the attitude, our approach does not rely on the knowledge (or reconstruction) of the system orientation as usually done in the existing literature. Instead, IMU and GPS measurements are directly incorporated in the control law. An important feature of the proposed strategy, is that the accelerometer is used to measure the apparent acceleration of the vehicle, as opposed to only measuring the gravity vector, which would otherwise lead to unexpected performance when the vehicle is accelerating (i.e. not in a hover configuration).     

Nanoporous zirconium oxide prepared using the supramolecular templating approach

Hexagonal (Hx-ZrO₂) and lamellar (L-ZrO₂) phases of zirconium oxide have been prepared using the supramolecular templating approach. Long chain primary alkyl amines led to the formation of lamellar phases, while quaternary ammonium surfactants gave hexagonal phases. The materials have been characterized by XRD, TG/DTG, IR, XPS, SEM and EDX techniques. The influence of various synthesis parameters such as (i) the ZrO₂ surfactant ratio, (ii) the surfactant/water ratio, (iii) the nature of surfactant, (iv) the crystallization temperature and (v) the crystallization time have been investigated. The final solid products were found to be thermally unstable regardless of their structure. Removal of the surfactant from the mesopores by solvent extraction without damaging the structure was not possible.     

Q2ABR: QoE‐aware adaptive video bit rate solution

In this paper, we propose a new adaptive bit rate (ABR) streaming method. This method is based on estimating and monitoring users' video streaming experience, their quality of experience (QoE). This ensures a good user QoE and optimises bandwidth utilisation by monitoring video buffer fill rate to ensure minimal data traffic. First, we achieve a QoE evaluation model based on network bandwidth, video segment representation, and dropped video frame rate parameters. Second, following our QoE evaluation model, we formulate an ABR method using the reinforcement learning (RL) paradigm to select video representations and using a breakpoint detection mechanism to monitor end‐user QoE variation. The proposed ABR method is called “QoE‐aware adaptive bit rate (Q2ABR)” and is composed of three individual modules, one for QoE estimation using machine learning methods, one for QoE variation monitoring using the breakpoint detection mechanism, and one for video representation selection using reinforcement learning. The design objective of Q2ABR is to ensure the overall QoE of these users while maintaining a minimum variation in the standard deviation of the users' QoE values. Third, the performance of the Q2ABR method is evaluated and compared with several existing ABR approaches in the literature using real traces that we collect on different transport scenarios (such as bus and train, among others). Since this method considers the user's perception of video quality as a regulator for optimising the overall video distribution network, good results are ensured in terms of the user's experience and buffer fill rate.     

Velocity‐free attitude stabilization with inertial vector measurements

This paper deals with the attitude stabilization problem of a rigid body, where neither the angular velocity nor the attitude is used in the feedback; only body‐referenced vector measurements are needed. The proposed control scheme is based on an angular velocity observer‐like system relying solely on vector measurements. The proposed controller ensures almost global asymptotic stability and provides some interesting performance properties through an appropriate tuning of the control gains. The performance and effectiveness of the proposed control scheme are illustrated via simulation results where the control gains are adjusted using a nonlinear optimization. Copyright © 2015 John Wiley & Sons, Ltd.