Complete oxidation of methane at low temperature over Pt and Pd catalysts for the abatement of lean-burn natural gas fuelled vehicles emissions: influence of water and sulphur containing compounds

The catalytic activity of fresh Pd and Pt catalysts supported on γ-alumina in the complete oxidation of CH₄ traces under lean-burn conditions was studied in the presence or the absence of water or H₂S. Steam-aged catalysts were also studied in order to simulate long-term ageing in real lean-burn natural gas fuelled vehicles (NGVs) exhaust conditions. Without water or H₂S added to the feed, Pd catalysts exhibit a superior catalytic activity in methane oxidation compared to Pt ones, whatever the catalysts were fresh or aged. The addition of 10 vol.% water vapour to the feed strongly affects the activity of the fresh Pd catalyst, thus being only slightly more efficient than the fresh Pt one. H₂S has a strong poisoning effect on the catalytic activity of Pd catalysts, while Pt catalysts are more resistant. The fresh H₂S-poisoned Pd/Al₂O₃ catalyst was studied by TPD in O₂/He. Poisoning species decompose above 873 K as SO₂ and O₂ in relative concentrations consistent with the decomposition of surface sulphate species. However, a treatment in O₂/He at temperatures as high as 923 K does not allow the complete regeneration of the catalytic activity of H₂S-poisoned Pd/Al₂O₃. A mechanism involving the poisoning of PdO by sulphate species is proposed. Different diffusion processes by which these sulphate species can migrate back and forth between PdO and the support, depending on the experimental conditions, are suggested.     

Risk in Transport Investments

We discuss how the standard Cost-Benefit Analysis should be modified in order to take risk (and uncertainty) into account. We propose different approaches used in finance (Value at Risk, Conditional Value at Risk, Downside Risk Measures, and Efficiency Ratio) as useful tools to model the impact of risk in project evaluation. After introducing the concepts, we show how they could be used in CBA and provide some simple examples to illustrate how such concepts can be applied to evaluate the desirability of a new project infrastructure.     

Alumina-, niobia-, and niobia/alumina-supported NiMoS catalysts: Surface properties and activities in the hydrodesulfurization of thiophene and hydrodenitrogenation of 2,6-dimethylaniline

The activity of NiMoS catalysts supported on niobia, alumina, and niobia/alumina was compared for the thiophene hydrodesulfurization (HDS) and 2,6-dimethylaniline (2,6-DMA) hydrodenitrogenation (HDN) reactions. To evaluate the acidity of the supports and identify the nature of the sulfide sites, adsorption of 2,6-dimethylpyridine, pyridine, and CO was performed and followed by IR spectroscopy. This study has shown that with niobia as a support, the activity of NiMoS catalysts in thiophene HDS and in HDN of 2,6-DMA was no longer promoted by the synergy between Ni and Mo. The absence of synergy between molybdenum and nickel on niobia can be explained by the strong interaction of each metal with niobia at the expense of interaction with each other. Moreover, it has been shown that on a niobia/alumina support, the formation of the NiMoS phase can be directly linked to the presence of alumina not covered by niobia. However, niobia is an interesting support for the HDN of 2,6-DMA, because it favors the formation of xylene through direct ammonia elimination involving low H₂ consumption. The activity for xylene formation on niobia is linked to the electron-deficient nature of the Mo sulfide site, as demonstrated by CO adsorption followed by IR.     

Complete Oxidation of Methane at Low Temperature over Pt Catalysts Supported on High Surface Area SnO2

The catalytic activity of Pt catalysts supported on high surface area tin(IV) oxide in the complete oxidation of CH₄ traces under lean conditions at low temperature was studied in the absence and in the presence of water (10 vol.%) or H₂S (100 vol.ppm). Their catalytic properties were compared to those of Pd/Al₂O₃ and Pt/Al₂O₃. In the absence of H₂S in the feed, Pt/SnO₂appears as a very promising catalyst for CH₄ oxidation, being even significantly more active under wet conditions than the best reference catalyst, Pd/Al₂O₃. Catalysts steamed-aged at 873 K were also studied in order to simulate long term ageing in real lean-burn NGV exhaust conditions. To this respect, Pt/SnO₂ is slightly less resistant than Pd/Al₂O₃. In the presence of H₂S, Pt/SnO₂catalysts are rapidly and almost completely poisoned, comparably to Pd/Al₂O₃and the catalytic activity is hardly restored upon oxidising treatment below 773 K. A synergetic effect between Pt and specific surface SnO₂sites active in CH₄oxidation is proposed to explain the superior catalytic behaviour of Pt/SnO₂.     

Health monitoring of marine composite structural joints using fibre optic sensors

This paper describes a methodology for the health monitoring of composite marine joint structures based on strain measurements under operational loading using embedded fibre Bragg grating sensors. Finite element modelling indicated that the presence of a disbond significantly altered the bond-line longitudinal strain distribution. This was verified qualitatively through an experimental test program. The experimental results are examined in relation to the FE predictions and the implications for a practical strain-based SHM system are discussed. A technique is developed, based on novel signal processing and statistical outlier detection. This enables the sensor measurements to be used for damage detection without reference to a high-fidelity numerical model of the structure which is often difficult and resource-intensive to generate. The technique is shown to provide successful damage diagnoses with an acceptable level of accuracy. Further improvement in diagnostic accuracy may be achieved by increasing the sensor density.     

Individual Stair Ascent and Descent Walk Speeds Measured in a Korean High-Rise Building

The purpose of this study was to collect and analyze individual unimpeded stair ascent and descent walk speeds for the Korean population. To collect these data, a full-scale experiment was conducted in a 50-storey residential building in Korea involving 30 male and 30 female participants with an average age of 23.4 years. Each participant was required to ascend 50 floors and after a suitable rest period was then required to descend 50 floors using the stairs. Arrival times on each floor were recorded using video cameras, allowing floor by floor walk speeds to be determined and to assess whether fatigue affected the descent/ascent. The average descent speed for the male and female population was 0.83 m/s and 0.74 m/s, respectively, while the average ascent speed was 0.66 m/s and 0.48 m/s. However, there was no significant relationship between body mass index and stair walk speed or unimpeded horizontal walk speed and stair walk speed. During the descent, 50% of the population displayed a decrease in the walk speed over the final half of the descent with a maximum decrease of some 19%. However, some 50% of the population increased their travel speed during the final half of the descent. During the ascent, all participants decreased their speed over the first 20 floors by an average of approximately 60%. Implications of these findings for evacuation modeling/simulation are discussed.     

Penalty Approximation for Dynamical Systems Submitted to Multiple Non-Smooth Constraints

We consider discrete mechanical systems subject to perfect unilateral constraints. Moreau's impact law uses the decomposition of the velocity on the normaland tangent cones to the set of admissible positions at the impact point, and it iswell-known that this gives the only possible rule in the case of a singleperfect unilateral constraint. In the multi-constraint case, there areother possible energetically and geometrically consistant impact laws. Weshow here that in a number of cases, the limiting behavior of impact asits rigidity tends to infinity is given by Moreau's rule, i.e., in a more mathematical language, we justify this impact law by a penalty approach.First we describe the penalty method, then we apply it to amulti-constraint model problem. We choose an overdamped approximationand we obtain Moreau's rule for inelastic shocks in the limit. Finally,we present the computational drawbacks of the penalty method.     

Determination of the formation constant of ATP—cobalt(II) complex(ATP—Co)2− by A′pH stat′ titration method

A technique of pH titration is used for the study of the formation of the ATP Co^2? complex at diverse temperatures. The stability constants, as also the corresponding thermodynamic quantities, obtained for an ionic strength 0.2 in tetramethylammonium bromide are reported and compared with these of ATP Mn^2? and ATP Mg^2? complexes.     

Screening of genetically modified organisms and specific detection of Bt176 maize in flours and starches by PCR-enzyme linked immunosorbent assay

Polymerase chain reaction (PCR)-enzyme linked immunosorbent assays (ELISAs) targeting either the 35S promoter or the Bt176 specific junction sequence were developed to screen for the presence of genetically modified organisms (GMOs) and specifically detect Bt176 maize in flours and starches. Two additional PCR-ELISA assays were developed to validate the results: one, based on the detection of the maize alcohol dehydrogenase 1 promoter specifically detected the presence of maize, and the other, based on the detection of a conserved sequence of plants ( 26S ribosomal RNA gene), validated the extracted DNA amplification. The PCR-ELISA assays developed here were highly specific and found to be as sensitive as the reference Southern hybridisation assay. The PCR-ELISA tests were at least 6 times more sensitive than gel electrophoresis and allowed 0.1% GMOs to be detected in Bt176, Bt11, Mon810 maize and Roundup Ready soybean. The PCR-ELISA tests are a method of choice for GMO screening and identifying Bt176 maize in flours and native starches. They may offer a cheaper alternative to the expensive real-time PCR assays and may be useful in laboratory GMO monitoring.