688 research outputs found
Conception améliorée et caractérisation numérique des pompes submersibles de type sm : prise en compte des forces axiales et radiales, des contraintes, des déformations et des vibrations mécaniques induites
L'utilisation de la pompe submersible Ă grande pression est liĂ©e Ă des sollicitations Ă©levĂ©es sur ses Ă©quipements; ainsi sa conception a toujours Ă©tĂ© un grand dĂ©fi en raison des performances Ă atteindre. En effet, pour fabriquer ces pompes de maniĂšre optimale, les paramĂštres essentiels des composants doivent ĂȘtre dĂ©terminĂ©s tout en analysant simultanĂ©ment les forces axiales et radiales, les contraintes, les dĂ©formations et les vibrations induites. La sous-estimation ou lâomission de ces Ă©lĂ©ments lors de la phase de conception peut affecter le bon dimensionnement de l'arbre de la pompe et de ses paliers. De ce fait, le but de cette recherche est de dĂ©velopper des approches numĂ©riques fiables permettant de dĂ©terminer les forces axiales et radiales, les dĂ©formations, les contraintes et les vibrations induites dans les pompes submersibles de type SM. Lâutilisation de ces approches dans la conception desdites pompes permet Ă©galement dâamĂ©liorer davantage ses performances en ce qui concerne la hauteur manomĂ©trique, la puissance Ă lâarbre et le rendement tout en augmentant la fiabilitĂ© et la durĂ©e de vie des roulements et/ou des coussinets des paliers de lâarbre de pompe. Le dimensionnement part du point de conception caractĂ©risĂ© par un dĂ©bit de 141 m3/h, une hauteur manomĂ©trique de 92 m et une vitesse de rotation de 3600 tr/min. AprĂšs avoir dĂ©terminĂ© les diffĂ©rents paramĂštres gĂ©omĂ©triques des impulseurs, des diffuseurs et de lâarbre; un modĂšle 3D de la pompe a Ă©tĂ© obtenu dans le domaine solide et fluide. Les simulations numĂ©riques ont Ă©tĂ© rĂ©alisĂ©es et les rĂ©sultats obtenus ont Ă©tĂ© validĂ©s en les comparant avec les rĂ©sultats expĂ©rimentaux provenant de l'entreprise Technosub. Ainsi, les forces axiales, radiales et les couples rĂ©sultant des Ă©coulements du liquide dans l'impulseur deviennent des forces induites sur lâarbre de la pompe et permettent de dĂ©terminer les contraintes, les dĂ©formations et les vibrations mĂ©caniques sur lâarbre en rotation. Les analyses sur lâimpact du diamĂštre externe des impulseurs, du nombre d'Ă©tages de la pompe submersible et de la vitesse de rotation ont Ă©tĂ© rĂ©alisĂ©es dans lâoptique dâamĂ©liorer la conception de la pompe submersible de type SM. AprĂšs lâanalyse des rĂ©sultats, il convient de noter que les paramĂštres sĂ©lectionnĂ©s ont une influence directe sur la hauteur manomĂ©trique, la puissance Ă l'arbre, le rendement, la force axiale et radiale ainsi que les contraintes et les dĂ©formations induites dans la pompe
An international laboratory comparison of dissolved organic matter composition by high resolution mass spectrometry: Are we getting the same answer?
High-resolution mass spectrometry (HRMS) has become a vital tool for dissolved organic matter (DOM) characterization. The upward trend in HRMS analysis of DOM presents challenges in data comparison and interpretation among laboratories operating instruments with differing performance and user operating conditions. It is therefore essential that the community establishes metric ranges and compositional trends for data comparison with reference samples so that data can be robustly compared among research groups. To this end, four identically prepared DOM samples were each measured by 16 laboratories, using 17 commercially purchased instruments, using positive-ion and negative-ion mode electrospray ionization (ESI) HRMS analyses. The instruments identified ~1000 common ions in both negative- and positive-ion modes over a wide range of m/z values and chemical space, as determined by van Krevelen diagrams. Calculated metrics of abundance-weighted average indices (H/C, O/C, aromaticity, and m/z) of the commonly detected ions showed that hydrogen saturation and aromaticity were consistent for each reference sample across the instruments, while average mass and oxygenation were more affected by differences in instrument type and settings. In this paper we present 32 metric values for future benchmarking. The metric values were obtained for the four different parameters from four samples in two ionization modes and can be used in future work to evaluate the performance of HRMS instruments
Analysis of the P. lividus sea urchin genome highlights contrasting trends of genomic and regulatory evolution in deuterostomes
Sea urchins are emblematic models in developmental biology and display several characteristics that set them apart from other deuterostomes. To uncover the genomic cues that may underlie these specificities, we generated a chromosome-scale genome assembly for the sea urchin Paracentrotus lividus and an extensive gene expression and epigenetic profiles of its embryonic development. We found that, unlike vertebrates, sea urchins retained ancestral chromosomal linkages but underwent very fast intrachromosomal gene order mixing. We identified a burst of gene duplication in the echinoid lineage and showed that some of these expanded genes have been recruited in novel structures (water vascular system, Aristotle's lantern, and skeletogenic micromere lineage). Finally, we identified gene-regulatory modules conserved between sea urchins and chordates. Our results suggest that gene-regulatory networks controlling development can be conserved despite extensive gene order rearrangement
Measurements of branching fraction ratios and CP-asymmetries in suppressed B^- -> D(-> K^+ pi^-)K^- and B^- -> D(-> K^+ pi^-)pi^- decays
We report the first reconstruction in hadron collisions of the suppressed
decays B^- -> D(-> K^+ pi^-)K^- and B^- -> D(-> K^+ pi^-)pi^-, sensitive to the
CKM phase gamma, using data from 7 fb^-1 of integrated luminosity collected by
the CDF II detector at the Tevatron collider. We reconstruct a signal for the
B^- -> D(-> K^+ pi^-)K^- suppressed mode with a significance of 3.2 standard
deviations, and measure the ratios of the suppressed to favored branching
fractions R(K) = [22.0 \pm 8.6(stat)\pm 2.6(syst)]\times 10^-3, R^+(K) =
[42.6\pm 13.7(stat)\pm 2.8(syst)]\times 10^-3, R^-(K)= [3.8\pm 10.3(stat)\pm
2.7(syst]\times 10^-3, as well as the direct CP-violating asymmetry A(K) =
-0.82\pm 0.44(stat)\pm 0.09(syst) of this mode. Corresponding quantities for
B^- -> D(-> K^+ pi^-)pi^- decay are also reported.Comment: 8 pages, 1 figure, accepted by Phys.Rev.D Rapid Communications for
Publicatio
Comparison of PET metabolic indices for the early assessment of tumour response in metastatic colorectal cancer patients treated by polychemotherapy
Measurement of inclusive production in hadronic decays
An analysis is presented of inclusive \pi^0 production in Z^0 decays measured with the DELPHI detector. At low energies, \pi^0 decays are reconstructed by \linebreak using pairs of converted photons and combinations of converted photons and photons reconstructed in the barrel electromagnetic calorimeter (HPC). At high energies (up to x_p = 2 \cdot p_{\pi}/\sqrt{s} = 0.75) the excellent granularity of the HPC is exploited to search for two-photon substructures in single showers. The inclusive differential cross section is measured as a function of energy for {q\overline q} and {b \bar b} events. The number of \pi^0's per hadronic Z^0 event is N(\pi^0)/ Z_{had}^0 = 9.2 \pm 0.2 \mbox{(stat)} \pm 1.0 \mbox{(syst)} and for {b \bar b}~events the number of \pi^0's is {\mathrm N(\pi^0)/ b \overline b} = 10.1 \pm 0.4 \mbox{(stat)} \pm 1.1 \mbox{(syst)} . The ratio of the number of \pi^0's in b \overline b events to hadronic Z^0 events is less affected by the systematic errors and is found to be 1.09 \pm 0.05 \pm 0.01. The measured \pi^0 cross sections are compared with the predictions of different parton shower models. For hadronic events, the peak position in the \mathrm \xi_p = \ln(1/x_p) distribution is \xi_p^{\star} = 3.90^{+0.24}_{-0.14}. The average number of \pi^0's from the decay of primary \mathrm B hadrons is found to be {\mathrm N} (B \rightarrow \pi^0 \, X)/\mbox{B hadron} = 2.78 \pm 0.15 \mbox{(stat)} \pm 0.60 \mbox{(syst)}
Search for new phenomena using single photon events in the DELPHI detector at LEP
Data are presented on the reaction \epem~\into~\gamma + no other detected particle at center-of-mass energies, \sqs = 89.48 GeV, 91.26 GeV and 93.08 GeV. The cross section for this reaction is related directly to the number of light neutrino generations which couple to the \zz boson, and to several other phenomena such as excited neutrinos, the production of an invisible `X' particle, a possible magnetic moment of the tau neutrino, and neutral monojets. Based on the observed number of single photon events, the number of light neutrinos which couple to the \zz is measured to be N_\nu = 3.15 \pm 0.34. No evidence is found for anomalous production of energetic single photons, and upper limits at the 95\% confidence level are determined for excited neutrino production (BR < 4-9 \times 10^{-6}), production of an invisible `X' particle (\sigma < 0.1 pb), and the magnetic moment of the tau neutrino (< 5.2 \times 10^{-6} \mu_B). No event with the topology of a neutral monojet is found, and this corresponds to the limit \sigma < 0.044/\epsilon pb at the 95\% confidence level, where \epsilon is the unknown overall monojet detection efficiency
Measurement of the B oscillation frequency using kaons, leptons and jet charge
A measurement of the mass difference, \Delta m_d, between the two physical \mbox{B}^0_d states has been obtained from the analysis of the impact parameter distribution of a lepton emitted at large transverse momentum (p_t) relative to the jet axis and from the analysis of the flight distance distribution of secondary vertices tagged by either a high p_t lepton or an identified kaon. In the opposite hemisphere of the event, the charge of the initial quark has been evaluated using a high p_t lepton, a charged kaon or the mean jet charge. With 1.7 million hadronic Z^0 decays recorded by DELPHI between 1991 and 1993, \Delta m_d is found to be: \Delta m_d = 0.531^{+0.050}_{-0.046} ~(stat.) \pm 0.078 ~(syst.) ~ {\mathrm{ps}}^{-1} \,
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