Kinematic modelling of a 3-axis NC machine tool in linear and circular interpolation

Machining time is a major performance criterion when it comes to high-speed machining. CAM software can help in estimating that time for a given strategy. But in practice, CAM-programmed feed rates are rarely achieved, especially where complex surface finishing is concerned. This means that machining time forecasts are often more than one step removed from reality. The reason behind this is that CAM routines do not take either the dynamic performances of the machines or their specific machining tolerances into account. The present article seeks to improve simulation of high-speed NC machine dynamic behaviour and machining time prediction, offering two models. The first contributes through enhanced simulation of three-axis paths in linear and circular interpolation, taking high-speed machine accelerations and jerks into account. The second model allows transition passages between blocks to be integrated in the simulation by adding in a polynomial transition path that caters for the true machining environment tolerances. Models are based on respect for path monitoring. Experimental validation shows the contribution of polynomial modelling of the transition passage due to the absence of a leap in acceleration. Simulation error on the machining time prediction remains below 1%

Modeling and simulation of high speed milling centers dynamics

High speed machining is a milling operation in industrial production of aeronautic parts, molds and dies. The parts production is being reduced because of the slowing down of the machining resulting from the tool path discontinuity machining strategy. In this article, we propose a simulation tool of the machine dynamic behavior, in complex parts machining. For doing this, analytic models have been developed expressing the cutting tool feed rate. Afterwards, a simulation method, based on numerical calculation tools, has been structured. In order to validate our approach, we have compared the simulation results with the experimental ones, for the same examples

Pilot optical alignment

PILOT (Polarized Instrument for Long wavelength Observations of the Tenuous interstellar medium) is a balloonborne astronomy experiment designed to study the polarization of dust emission in the diffuse interstellar medium in our Galaxy. The PILOT instrument allows observations at wavelengths 240 μm and 550 μm with an angular resolution of about two arcminutes. The observations performed during the two first flights performed from Timmins, Ontario Canada, and from Alice-springs, Australia, respectively in September 2015 and in April 2017 have demonstrated the good performances of the instrument. Pilot optics is composed of an off axis Gregorian type telescope combined with a refractive re-imager system. All optical elements, except the primary mirror, which is at ambient temperature, are inside a cryostat and cooled down to 3K. The whole optical system is aligned on ground at room temperature using dedicated means and procedures in order to keep the tight requirements on the focus position and ensure the instrument optical performances during the various phases of a flight. We’ll present the optical performances and the firsts results obtained during the two first flight campaigns. The talk describes the system analysis, the alignment methods, and finally the inflight performances

Pilot optical alignment

PILOT (Polarized Instrument for Long wavelength Observations of the Tenuous interstellar medium) is a balloonborne astronomy experiment designed to study the polarization of dust emission in the diffuse interstellar medium in our Galaxy. The PILOT instrument allows observations at wavelengths 240 μm (1.2THz) with an angular resolution about two arc-minutes. The observations performed during the first flight in September 2015 at Timmins, Ontario Canada, have demonstrated the optical performances of the instrument

Intégration de pics de contamination de durée et d’intensité variables par le « Polar Organic Chemical Integrative Sampler »

International audienceContamination level estimate can vary abruptly, depending on season and hydrology of the river at the sampling moment. The Polar Organic Chemical Integrative Sampler (POCIS) may integrate contamination peaks of about 3 days for moderately polar compounds (log Kow = 2-3) [3]. Concerning shorter contamination peaks (less than 1 hour) generated by punctual pollutions or a brutal intake of pesticides in a river (soil leaching, for example), interrogations about its reactivity (e.g. lag time) is still remaining. In this context, a laboratory calibration was made for three different contamination peak patterns, with variable intensity and duration. This experiment was led over a total exposure time of 14 days, and with a selection of 15 pesticides which covering different polarities (log Kow = 0.6-4.7) and classes (herbicides, fungicides, insecticides). Finally, the data showed different accumulation kinetic profiles, with phenomena like burst effect or lag effect, depending on physical-chemical properties of the substances and the exposition duration

Contamination en polychlorobiphenyles (PCB) des anguilles du système fluvio estuarien de la Gironde

[Departement_IRSTEA]MA [TR1_IRSTEA]QSA / DYMECOLes polluants organiques persistants (POP) sont des substances chimiques faiblement biodégradables qui possèdent des propriétés physico-chimiques qui leur confèrent un fort potentiel de bioaccumulation par les organismes. Parmi ces composés, les polychlorobiphényles (PCB) sont des molécules chlorées ubiquistes particulièrement rémanentes ; bien qu'interdits depuis la fin des années 1970, ils sont encore très présents à l'heure actuelle dans les écosystèmes aquatiques. Les travaux développés ont donc visé à caractériser d'une part la contamination en PCB des anguilles présentes dans le système estuarien et, d'autre part, la dynamique spatio-temporelle de cette contamination. Les composés étudiés ont été les 7 PCB indicateurs (CB 28, CB 52, CB 101, CB 118, CB 138, CB 153 et CB 180). Ces PCB sont des PCB dits "globulaires" ne présentant pas le même type de toxicité que les PCB dits "dioxine like", mais ils sont de très bons marqueurs des mécanismes de transfert des POP dans les réseaux trophiques, et font l'objet de l'avis de l'AFSSA. Le niveau de contamination en PCB a ainsi été évalué sur un échantillonnage de 17 lots de civelles, et de 240 individus d'âges et de tailles variés réalisé sur l'ensemble du système fluvio-estuarien de la Gironde

Contamination en polychlorobiphenyles (PCB) des anguilles du système fluvio estuarien de la Gironde

[Departement_IRSTEA]MA [TR1_IRSTEA]QSA / DYMECOLes polluants organiques persistants (POP) sont des substances chimiques faiblement biodégradables qui possèdent des propriétés physico-chimiques qui leur confèrent un fort potentiel de bioaccumulation par les organismes. Parmi ces composés, les polychlorobiphényles (PCB) sont des molécules chlorées ubiquistes particulièrement rémanentes ; bien qu'interdits depuis la fin des années 1970, ils sont encore très présents à l'heure actuelle dans les écosystèmes aquatiques. Les travaux développés ont donc visé à caractériser d'une part la contamination en PCB des anguilles présentes dans le système estuarien et, d'autre part, la dynamique spatio-temporelle de cette contamination. Les composés étudiés ont été les 7 PCB indicateurs (CB 28, CB 52, CB 101, CB 118, CB 138, CB 153 et CB 180). Ces PCB sont des PCB dits "globulaires" ne présentant pas le même type de toxicité que les PCB dits "dioxine like", mais ils sont de très bons marqueurs des mécanismes de transfert des POP dans les réseaux trophiques, et font l'objet de l'avis de l'AFSSA. Le niveau de contamination en PCB a ainsi été évalué sur un échantillonnage de 17 lots de civelles, et de 240 individus d'âges et de tailles variés réalisé sur l'ensemble du système fluvio-estuarien de la Gironde

易圖象與易詮釋

International audienceThe present work describes the validation of an easy, fast and efficient precolumn derivatization method for the quantification of oligosides, mannose and galactose obtained by degradation of galactomannans. This work combines an acid hydrolysis and an enzymatic degradation of natural galactomannans with the quantification of released residues by reversed-phase HPLC-UV, the most usual HPLC system in laboratories. In case of enzymatic degradation, mannotetraose has been detected and quantified for the first time, and an application to the evaluation of the galactosyl distribution in galactomannans is proposed. After an acidic hydrolysis, this method also allowed to obtain the mannose/galactose (M/G) ratio

Intégration de pics de contamination d’intensité et de durée variables par le « Polar Organic Chemical Integrative Sampler »

[Departement_IRSTEA]Eaux [TR1_IRSTEA]BELCAInternational audienceNowadays, pesticides, considering their efficiency on animal and plant parasites, represent considerable progress in food resources management and public health improvement. However, due to intensive use, the three environment compartments (water, air, soil) are contaminated with worrying consequences for human being and ecosystem. In order to conserve and restore the condition of aquatic environments, the European Water Framework Directive (WFD) was adopted in 2000 by the European Union. Indeed, monitoring networks - such as Water Agencies - proceed to regular monitoring, performing spot water sampling up to 12 times a year. But, there are still questions about the spatial and temporal representativeness of this type of sampling. Actually, contamination level in rivers can vary abruptly, depending on season and hydrology at the sampling moment. Thus, contamination peaks could be undetected by monitoring networks, generating a partial snapshot and then estimation of water quality. Passive sampling techniques are proposed and developed to obtain better representativeness of the contamination level, providing average concentration over time with integration of peculiar events like contamination peaks. In this study, the Polar Organic Chemical Integrative Sampler (POCIS) with different king of membranes was considered. This tool, widely used for polar pesticides sampling (0 < log Kow < 4) (Alvarez et al. 2004), allows pre-concentration in situ of analytes and presents an integrative capacity over several week. Its scope and its technical limitations are actually well documented (Lissalde et al. 2011). Furthermore, it was proved that this device may integrate contamination peaks relatively prolonged (about 3 days) for moderately polar compounds (log Kow = 2-3) (Mazzella et al. 2008). Concerning shorter contamination peaks (few hours-few days) generated by punctual pollutions, interrogations about its reactivity (e.g. lag time) is still remaining. This study aimed to show the POCIS reactivity for three different contamination peak patterns, with variable intensity and duration, over a total exposure period of 14 days. For this experimentation under laboratory controlled conditions, fifteen pesticides covering different polarities (log Kow=0-5) and groups (herbicides, fungicides, insecticides) were selected. The data showed different accumulation kinetic profiles, depending on physico-chemical characteristics of the substances and the exposition duration. Some compounds presented a lag effect, or on the contrary a burst effect. For seven compounds, POCIS sampled correctly contamination peaks, which show the ability of this device to sample fleeting events

ASE extraction method for simultaneous carbon and nitrogen stable isotope analysis in soft tissues of aquatic organisms

Since lipids are depleted in C-13 relative to proteins and carbohydrates, variations in lipid composition among species and within individuals significantly influence delta C-13 and may result in misleading ecological interpretations. Whereas lipid extraction before IRMS analysis constitutes a way of stable isotope result lipid-normalisation, such a procedure was given up because of the un-controlled effects of the methods used (i.e., "Bligh & Dyer", Soxhlet, etc.) on delta N-15. The aim of this work was to develop a simple, rapid and efficient lipid extraction method allowing for simultaneous C and N stable isotope analysis in the biological soft tissues of aquatic Organisms. The goal was to be free from the lipid influence on delta C-13 values without interfering with delta N-15 values. For that purpose, the modern automated pressurized liquid extraction technique ASE (accelerated solvent extraction) was selected. Eel muscles representative of a broad range of far contents were extracted via ASE by using different semi-polar solvents (100% dichloromethane and 80% n-hexane/20% acetone) and by operating at different temperature (ambient temperature and 100 degrees C) and pressure (750 and 1900 psi) conditions. The results were discussed in terms of lipid extraction efficiency as well as delta C-13 and delta N-15 variability