IDENTIFICATION OF NITROGEN COMPOUNDS AND THEIR EVOLUTIONDURINGAGEING NABSENCE ANDPRESENCE OF ADDITIVES EFFICIENCYOFHYDROTREATMENT

As established by several previous works, nitrogen compounds play a prominent role in the evolution of middle distillates containing cracked components, particularly regarding sediment formation and color evolution.

In a first part, this paper describes and compares stability properties of fuel blends using both an accelerated ageing method at 120°C (248°F ) and long term storage methods at 43°C(110°F) -ASTM 0 4625 - and at ambient temperature. Effectiveness of stabilizing additives is also evaluated. In mixtures containing LCOs, insoluble products are formed progressively during ageings, more or less rapidly according to the chemical constitution of the mixtures.

Then, it reports the complete identification of nitrogen compounds using gas chromatography equipped with a selective nitrogen detector and mass spectrometry showing that in light cycle oils, alkyl indoles and carbazoles are the main families.

Evolution of these compounds was followed kinetically during ageings in absence and presence of additives and alkyl indoles appeared as the moat evolutionary.

It appeared that some additives avoided evolutions of alkyl indoles without preventing sediment formation and color evolution. Oxidation mechanism involving nitrogen compounds should not be the only one to explain the storage evolutions of middle distillates.

Hydrotreatment converts all the alkyl indoles of LCO and prevents coloration end deposits in the storage of the mixtures of steaight-run distillates and LCOs.     

A distributed approach for access and visibility task with a manikin and a robot in a virtual reality environment

This paper presents a new method, based on a multi-agent system and on a digital mock-up technology, to assess an efficient path planner for a manikin or a robot for an access and visibility task taking into account ergonomic constraints or joint and mechanical limits. In order to solve this problem, the human operator is integrated in the process optimization to contribute to a global perception of the environment. This operator cooperates, in real time, with several automatic local elementary agents. The result of this work validates solutions through the digital mock-up; it can be applied to simulate maintainability and mountability tasks.     

Elastic properties of polycrystalline gold thin films: Simulation and X-ray diffraction experiments

The elastic behavior of supported gold thin films has been studied using a framework in which the elastic interaction between grains and the actual structure of the film (i.e. preferential grain orientation and grain shape) are taken into account. Experiments were carried out using synchrotron X-ray diffraction combined with in-situ tensile testing and thereafter, no assumptions on the residual stress state and on the stress-free lattice parameter a₀ have to be made. Modeling of grain elastic interactions is based on the extension of Eshelby-Kröner model, which allows for estimating the elastic behavior of polycrystals considering the texture and the shape of the crystallites. Flat-disc shaped grains arrangement is shown to yield the best representation of the elastic behavior of the fiber-textured gold thin films composed of columnar grains. This non-intuitive representation results from free-surface effect.     

In situ regeneration of the Ni-based catalytic reformer of a 5 kW PEMFC system

The paper reports the results of on-site regeneration catalytic bed of the natural gas reformer in a 5 kW PEM fuel cell system. The Ni catalyst previously poisoned by sulphur from the available natural gas, could be re-activated by injection of pure water steam, following the method developed for industrial reformers using the same metal catalyst: this method was shown to be perfectly efficient, provided no natural gas was fed during the operation. Results of the tests conducted are presented and discussed in relation to published data on S-sorption on Ni surfaces.     

New integrated buried laser-ridge modulator with identical active layer

Integrated laser modulators are attractive devices for wavelength-division-multiplexing optical systems due to their compactness, high output power, and low cost. Their fabrication simplicity is a way to decrease further the transmitter cost and address new opening markets of short range and metropolitan networks. We report a new integration scheme electroabsorption-modulator distributed feedback (DFB) laser based on well-established industrial solutions for discrete buried ridge (BRS) DFB lasers and discrete shallow ridge modulators. Processing simplification with an identical active layer has been possible due to a good behavior of strongly positively detuned BRS lasers. The integrated devices demonstrated 30-dB extinction ratio with 10-GHz bandwidth and P/sub out/=10 dBm for emission in 1.55-/spl mu/m range.     

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     

Fast and accurate pricing of discretely monitored barrier options by numerical path integration

Barrier options are financial derivative contracts that are activated or deactivated according to the crossing of specified barriers by an underlying asset price. Exact models for pricing barrier options assume continuous monitoring of the underlying dynamics, usually a stock price. Barrier options in traded markets, however, nearly always assume less frequent observation, e.g. daily or weekly. These situations require approximate solutions to the pricing problem. We present a new approach to pricing such discretely monitored barrier options that may be applied in many realistic situations. In particular, we study daily monitored up-and-out call options of the European type with a single underlying stock. The approach is based on numerical approximation of the transition probability density associated with the stochastic differential equation describing the stock price dynamics, and provides accurate results in less than one second whenever a contract expires in a year or less. The flexibility of the method permits more complex underlying dynamics than the Black and Scholes paradigm, and its relative simplicity renders it quite easy to implement.     

An efficient purification method for detonation nanodiamonds

This article reports the purification process of detonation soot to obtain pure nanodiamond powder. Nanodiamonds are synthesized by detonation using a high explosive mixture composed of trinitrotoluene and hexogen. The detonation of the charge leads to a powder containing nanodiamonds as well as metallic impurities and sp² carbon species. Further, to remove metallic particles, an unusual acidic treatment (hydrofluoric/nitric acids; i.e. fluorinated aqua regia) was set up. To eliminate sp² carbon species such as graphite and amorphous carbon, a thermal oxidation treatment was performed at 420 °C under air in a furnace during several hours. Transmission Electronic Microscopy, Raman spectroscopy, X-ray diffraction and Thermo-Gravimetric Analysis showed that this purification process is very efficient. From TGA measurements, a model of the carbon grain combustion was developed by considering graphitic shells surrounding the nanodiamond particles, and was used to demonstrate that the selective oxidation of graphite was experimentally realistic. Moreover, another model was set up from specific area measurements to evaluate the thickness of the functional groups surrounding the nanodiamonds after the oxidation of sp² carbonaceous species. The treatment described herein was achieved on several tens of grams of product and could be easily adapted to the industrial scale.     

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Further observation of leucocyte migration through the endothelium of venules in the posterior latissimus dorsi muscle of the quail-chick spinal cord chimeras

The migration of leucocytes through the walls of venules was examined in detail in the posterior latissimus dorsi muscle of quail-chick spinal cord chimeras, in which flaccid paralysis of the wings was observed. Examinations were made from the 70th to 80th day after hatching. Muscle fibers were degenerated and intramuscular nerve bundles destroyed. Massive leucocytes (almost lymphocytes) were found around the venules, depending on the passage of wandering leucocytes through the endothelium. Lymphocytes penetrated and were encased in the cytoplasm of the venular endothelial cell, and did not pass through the interendothelial junction. These findings suggest that, in the venules of the atrophied chimeric muscle, wandering leucocytes in the blood may pass through the endothelial cell body and migrate into the inflamed extravascular space.