Characterisation by TPR, XRD and NOx Storage Capacity Measurements of the Ageing by Thermal Treatment and SO2 Poisoning of a Pt/Ba/Al NOx-Trap Model Catalyst

The deactivation of a Pt/Ba/Al₂O₃ NO _x -trap model catalyst submitted to SO₂ treatment and/or thermal ageing at 800 °C was studied by H₂ temperature programmed reduction (TPR), X-ray diffraction (XRD) and NO _x storage capacity measurements.The X-ray diffractogram of the fresh sample exhibits peaks characteristic for barium carbonate. Thermal ageing leads to the decomposition of barium carbonate and to the formation of BaAl₂O₄. The TPR profile of the sulphated sample shows the presence of (i) surface aluminium sulphates, (ii) surface barium sulphates, (iii) bulk barium sulphates. The exposure to SO₂ after ageing leads to a small decrease of the surface barium-based sulphates, expected mainly as aluminate barium sulphates. This evolution can be attributed to a sintering of the storage material. TPR experiments also show that thermal treatment at 800 °C after the exposure to SO₂ involves the decomposition of aluminium surface sulphates to give mainly bulk barium sulphates, also pointed out by XRD. Thus, the thermal treatment at 800 °C leads to a stabilization of the sulphates.These results are in accordance with the NO _x storage capacity measurements. On non-sulphated catalysts, the treatment at 800 °C induces to a decrease of the NO _x storage capacity, showing that barium aluminate presents a lower NO _x storage capacity than barium carbonate. Sulphation strongly decreases the NO _x storage capacity of catalysts, whatever the initial thermal treatment, showing that barium sulphates inhibit the NO₂ adsorption. Moreover, the platinum activity for the NO to NO₂ oxidation is lowered by thermal treatments.     

QoS aggregation for service orchestrations based on workflow pattern rules and MCDM method: evaluation at design time and runtime

Service consumers satisfaction is considered today as one of the main concern to be ensured by service providers, especially with the spread of concurrency and the increase of functionally equivalent services. This satisfaction is closely related to quality of service (QoS) perceived by service consumers. In this context, we propose an approach to determine the satisfaction degree corresponding to the QoS of service-based applications, with regard to service consumers’ QoS expectations. Our approach is based on a preference model, which is built only on the basis of service consumer’s provided information. This preference model is also based on the 2-additive Choquet operator that takes into account preferential dependencies. In this paper, we target both design time and runtime aggregation of QoS of service-based applications.     

Using electric actuation and detection of oscillations in microcantilevers for pressure measurements

Response characteristics of a microcantilever, such as resonant frequency, amplitude, phase and quality factor, can be used for absolute pressure measurements in the range of 10⁻⁴ to 10³ Torr. To this end, it would be very convenient to have the resonance of the microcantilever actuated and detected electrostatically. Herein, we report the nonlinear dynamics of microcantilevers under varying pressure and different gases using the harmonic detection of resonance (HDR) technique [J. Gaillard, M.J. Skove, R. Ciocan, A.M. Rao, Electrical detection of oscillations in 340 microcantilevers and nanocantilevers, Rev. Sci. Instrum. 77 (2006) 073907]. The HDR technique exploits nonlinearities in the cantilever-counter electrode system to allow electrostatic actuation and detection of the responses of the microcantilever to the pressure and gas composition. In particular, the 2nd and 3rd harmonics of the measured charge on the cantilever are investigated. The microcantilever demonstrates a quality factor of 10,000 at 10⁻³ Torr, and a usable response in the range from 10⁻³ to 10³ Torr. The use of different harmonics can enable us to adjust the range of pressures over which the sensor has an efficacious response, enhancing its sensitivity to a particular environment. The experimental results are in reasonable agreement with theoretical calculations, despite the nonlinearities involved.     

Absolute calibration of photostimulable image plate detectors used as (0.5-20 MeV) high-energy proton detectors

In this paper, the absolute calibration of photostimulable image plates (IPs) used as proton detectors is presented. The calibration is performed in a wide range of proton energies (0.5-20 MeV) by exposing simultaneously the IP and calibrated detectors (radiochromic films and solid state detector CR39) to a source of broadband laser-accelerated protons, which are spectrally resolved. The final result is a calibration curve that enables retrieving the proton number from the IP signal.     

Dynamique des lasers à fibre dopée à I’erbium

The dynamics of the erbium doped fiber laser is analysed both experimentally and theoretically. This laser operates spontaneously in self-pulsing, in sinusoidal or in CW regime. Experiments have allowed to determine the control parameters : the cavity losses, the pumping rate and the ion pairs concentration. An antiphase dynamics is observed when the laser operates simultaneously at 1.55 µn and 1.536 µm. The self-pulsing behavior is attributed to a fast energy transfer which occurs between two neighboring ions (pair induced quenching). A simple model considering the active medium as a mixture of isolated ions and ions pairs is developped and leads to a good qualitative agreement with the experimental results.     

Overlap-freeness in infinite partial words

We prove that there exist infinitely many infinite overlap-free binary partial words containing at least one hole. Moreover, we show that these words cannot contain more than one hole and the only hole must occur either in the first or in the second position. We define that a partial word is $k$-overlap-free if it does not contain a factor of the form $xyxyx$ where the length of $x$ is at least $k$. We prove that there exist infinitely many 2-overlap-free binary partial words containing an infinite number of holes.     

Sign language applications: preliminary modeling

For deaf persons to have ready access to information and communication technologies (ICTs), the latter must be usable in sign language (SL), i.e., include interlanguage interfaces. Such applications will be accepted by deaf users if they are reliable and respectful of SL specificities—use of space and iconicity as the structuring principles of the language. Before developing ICT applications, it is necessary to model these features, both to enable analysis of SL videos and to generate SL messages by means of signing avatars. This paper presents a signing space model, implemented within a context of automatic analysis and automatic generation, which are currently under development.

Plasticity and fracture initiation in rubber-toughened poly(methyl methacrylate)

The deformation behavior of rubber toughened poly(methylmethacrylate), RT-PMMA, has been investigated in terms of the ability of the material to nucleate plasticity. Work-hardening rate parameter K measurements in the early stages of the nonelastic response in a constant strain-rate test are used to probe the development of micro shear zones as a function of rubber volume fraction. The results reveal the existence of a sharp transition from difficult to easy shear band nucleation for a critical rubber volume fraction V_c. This abrupt change in mechanical behavior also shows in the evolution of the critical stress intensity factor K measured at the onset of crack initiation. These findings are discussed in terms of the morphological parameters of the blends.     

Flaw detection close to the interface using ultrasonic echography

The detection of flaws by ultrasonic echography becomes difficult when the flaw is at a shallow depth. The time delay between the interface and flaw echos is less than the width of the impulse-response time of the transducer, and the flaw echo generally has an amplitude much smaller than the dominating interface echo. When the surface is not too rough, the interface echo can be assumed to be known, and its comparison with the signal interface and flaw echo permits the detection of the flaw. In this article it is shown that signal processing techniques allow small flaws to be detected very close to the surface (0.5 mm). Two methods are proposed, the first one is based on the minimization of the mean-square error, and the second on the spectral substraction of the two echos.This work has been supported by the French Ministry of Defense.     

GPU Shape Grammars

GPU Shape Grammars provide a solution for interactive procedural generation, tuning and visualization of massive environment elements for both video games and production rendering. Our technique generates detailed models without explicit geometry storage. To this end we reformulate the grammar expansion for generation of detailed models at the tesselation control and geometry shader stages. Using the geometry generation capabilities of modern graphics hardware, our technique generated massive, highly detailed models. GPU Shape Grammars integrate within a scalable framework by introducing automatic generation of levels of detail at reduced cost. We apply our solution for interactive generation and rendering of scenes containing thousands of buildings and trees.