Back-supported stratified flame propagation in lean and nonflammable mixtures

International audienceIn an effort to reduce pollutant emissions and increase energy efficiency, partially premixed combustion has been integrated into many new combustion technologies. The present study investigated lean back-supported flames in a stratified combustion regime. Outwardly propagating flames were observed following ignition under laminar stratification conditions generated in a constant volume vessel. The quantitative analysis of the flame properties relied on simultaneous PIV measurements to obtain local flame burning velocities and stretch rates and used anisole-PLIF measurements to calculate the equivalence ratio. Simultaneous OH-PLIF and OH-gradient measurements were used to differentiate between the burned gas boundaries and the active flame front. This differentiation was necessary to investigate the nonflammable mixture. Simultaneous OH-and anisole-PLIF measurements were used to estimate the thermal flame thickness. Two flame families were investigated: in family A the flame was ignited in a lean mixture (φ=0.6) with a rich stratification; in family B the mixture in the chamber was nonflammable. In rich mixtures ignition compensated for the non-equidiffusive effects of the lean propane flame. Both a flammable and a nonflammable mixture were investigated to evaluate the time scales of the back-supported propagation for the given stratification. The enhanced combustion regime allowed the flame to propagate with an active flame front, even in the nonflammable mixture for a few milliseconds before the flame extinguished

Assessing the differences between numerical methods and real experiments for the evaluation of reach envelopes of the human body

The use of static human body dimensions to assess the human accessibility is an essential part of an ergonomic approach in user-centered design. Assessments of reach capability are commonly performed by exercising external anthropometry of human body parts, which may be found in anthropometric databases, to numerically define the reach area of an intended user population. The result is a reach envelope determined entirely by the segment lengths, without taking into account external variables, as the nature of the task or the physical capacities of the subject, which may influence the results. Considering the body as a simple assembly of static parts of different anthropometry is limiting. In this paper, the limit of validity of this approach is assessed by comparing the reach envelopes obtained by this method to those obtained with a simple two-dimensional experimental reaching task of a panel of subjects. Forty subjects experimentally evaluated the reach, first with the body constrained and second unconstrained. Results were recorded and compared with those obtained numerically with a model, based on their own anthropometric characteristics, previously measured. A statistical study of the results allowed the definition of the shape of a confidence bound containing the real reach envelope. The results indicated important differences between the experiment and the numerical evaluation of the reach envelope.Comment: Colloque National AIP-Prim\'eca, Mar 201

Simultaneous measurements of PIV, anisole-PLIF and OH-PLIF for investigating back-supported stratified flame propagation in lean and nonflammable mixtures

International audienceIn an effort to reduce pollutant emissions and increase energy efficiency, partially premixed combustion has been integrated into many new combustion technologies. The present study investigated lean back-supported flames in a stratified combustion regime. This strategy leads to hybrid combustion regimes, ranging between fully premixed and fully non-premixed reactants, with a large panel of flame structures and properties requiring to be characterized. Outwardly propagating flames were observed following ignition under laminar stratification conditions generated in a constant volume vessel. The quantitative analysis of the flame properties relied on simultaneous PIV measurements to obtain local flame burning velocities and stretch rates and used anisole-PLIF measurements to calculate the equivalence ratio. Simultaneous OH-PLIF measurements were used to differentiate between the burned gas boundaries and the active flame front. This differentiation was necessary to investigate the nonflammable mixture. The OH-gradient measurement proved to be suitable for distinguishing burned gas interfaces from active flame fronts. Simultaneous OH-and anisole-PLIF measurements were used to estimate the thermal flame thickness. Two flame families were investigated: in family A the flame was ignited in a lean mixture (φ=0.6) with a rich stratification; in family B the mixture in the chamber was nonflammable. In rich mixtures ignition compensated for the non-equidiffusive effects of the lean propane flame and reinforced the flame's stretch resistance. Both a flammable and a nonflammable mixture were investigated to determine the time scales of the back-supported propagation for the given stratification. The enhanced combustion regime allowed the flame to propagate with an active flame front, even in the nonflammable mixture. Combustion continued for a few milliseconds before the flame extinguished. The richer the stratification, the longer the combustion lasted in the nonflammable mixture

Femoral deficiency reconstruction using a hydroxyapatite-coated locked modular stem. A series of 43 total hip revisions

SummaryIntroductionWe report a continuous prospective series of patients operated on for total hip prosthesis femoral component loosening involving a bone defect. Reconstruction was performed using a hydroxyapatite-coated locked modular stem. The study's objective was to assess medium term clinical and X-ray results obtained with this original concept.Materials and methodsThe patients included received a REEF® (DePuy) femoral implant for aseptic loosening or loosening associated with a periprosthetic fracture. Implantation was systematically accompanied by an extended trochanteric osteotomy (ETO). Patients were followed up prospectively by clinical and X-ray examination. Their loosening was graded at inclusion according to Vives’ classification as revised by SOFCOT in 1999. Analysis focused on actuarial implant survivorship, dislocation and the bone/implant interface.ResultsForty-three hips were included: mean follow-up was 58.2 months (12–92) and mean age at surgery was 72.4 years (37–94). The main indications were severe bone loss rated grade III (n=15) or IV (n=16) according to the SOFCOT classification. There was one long-term failure, involving implant fracture secondary to nonunion of the femoral shaft. Mean Postel and Merle d’Aubigné (PMA) clinical assessment score increased from six preoperatively to 14.5 at end of follow-up. X-ray analysis found no stem migration by end of follow-up. There was consistent consolidation of the ETO around the stem, except in one case of stem fracture which evolved into tight nonunion. In terms of metaphyseal integration, five patients showed radiolucency without evolution over follow-up, and eight had severe calcar cortical atrophy at end of follow-up. Mean 5-year actuarial survivorship was 97.7±2.3%, with a 2% incidence of dislocation.DiscussionThe complications rate was low, and results were comparable with those reported in the literature. The study confirmed the interest of the extended trochanteric osteotomy exposure and the effectiveness of the hydroxyapatite-coated interlocked modular stem concept in the treatment of hip prosthesis loosening with femoral bone loss (involving or not the cortex). On analysis, the one case of failure does not proscribe the surgical technique employed. Implant osseointegration was difficult to analyze. The extent of the surgical approach and of its corresponding sequels, combined with the complexity of adjusting the implant, however, restrict this surgical option indications to level III and IV cases of femoral loosening.Level of evidence: level IV; therapeutic study

Modelling and optimising the marginal expansion of an existing district heating network

Although district heating networks have a key role to play in tackling greenhouse gas emissions associated with urban energy systems, little work has been carried out on district heating networks expansion in the literature. The present article develops a methodology to find the best district heating network expansion strategy under a set of given constraints. Using a mixed-integer linear programming approach, the model developed optimises the future energy centre operation by selecting the best mix of technologies to achieve a given purpose (e.g. cost savings maximisation or greenhouse gas emissions minimisation). Spatial expansion features are also considered in the methodology. Applied to a case study, the model demonstrates that depending on the optimisation performed, some building connection strategies have to be prioritised. Outputs also prove that district heating schemes' financial viability may be affected by the connection scenario chosen, highlighting the necessity of planning strategies for district heating networks. The proposed approach is highly flexible as it can be adapted to other district heating network schemes and modified to integrate more aspects and constraints

Delle Società di Commercio : comento del titolo III libro I del codice di commercio : coll'aggiunta della giurisprudenza delle corti belgie / di M. Delangle ; 1. versione italiana de Giuseppe D'Angelo

FA156XXXI, 484 p. ; 27 c

Tristhiolato Pseudopeptides Bind Arsenic(III) in an AsS 3 Coordination Environment Imitating Metalloid Binding Sites in Proteins

The AsIII binding of two NTA-based tripodal pseudopeptides, possessing three cysteine (ligand L1) or D- penicillamine residues (ligand L2) as potential coordinating groups for soft semimetals or metal ions, was studied by experimental (UV, CD, NMR, and ESI-MS) and theoretical (DFT) methods. All of the experimental data, obtained with the variation of the AsIII:ligand concentration ratios or pH values in some instances, evidence the exclusive formation of species with an AsS3-type coordination mode. The UV-monitored titration of the ligands with arsenous acid at pH = 7.0 provided an absorbance data set that allowed for the determination of apparent stability constants of the forming species. The obtained stabilities (logK ' = 5.26 (AsL1) and logK ' = 3.04 (AsL2)) reflect high affinities, especially for the sterically less restricted cysteine derivative. DFT calculated structures correlate well with the spectroscopic results and, in line with the 1H NMR data, indicate a preference for the all-endo conformers resembling the AsIII environment at the semimetal binding sites in various metalloproteins

Couplage de la PIV et de la PLIF de OH et d'anisole pour l'étude d'une flamme se propageant dans une stratification de mélange laminaire

International audienceLa combustion partiellement prémélangée est introduite dans de nombreuses technologies récentes de combustion pour réduire les émissions de polluants et augmenter l'efficacité énergétique. Ce papier s'intéresse à la combustion stratifiée prémélangée. Des mesures simultanées de PIV, PLIF-OH et PLIF-anisole ont été utilisées pour étudier la propagation de flamme allumée par étincelle dans une stratification de mélange. Deux familles de flammes propane/air ont été considérées en fonction que la flamme se propage vers un milieu pauvre inflammable ou ininflammable. Dans les deux cas nous avons pu montrer une amélioration de la combustion dans les zones pauvres, avec temporairement avant extinction, des propagations de flamme dans des mélanges ininflammables