Estimation of Air-Pressure Drop in Inclined Penstocks during an Emergency Closure of Intake Gates

Hydroelectric power is an important source of energy. This is particularly true for Quebec and some other provinces in Canada. In the event of a combination of power trip and wicket gate blockage, as an emergency response, it is necessary to close the intake gates in order to stop water flow through the penstock to the unit. Such emergency closure can cause air pressure inside the penstock chamber to drop so significantly that the safety risks to the power station structures and facilities become unacceptable. The purpose of this study is to develop analysis methods for the assessment of air pressure drop in emergency closure. The scope of this research work covers the determination of the following time-dependent quantities: water discharge beneath a sluice gate, dry air flow through air vents leading to the penstock chamber, amount of air entrained by turbulent water motions through the penstock, and the resultant changes of air pressure in the penstock chamber. The analyses are based on the energy principle and take into account a large number of variables including the upstream and downstream water levels, the geometry of the hydraulic passage, the time rate of gate closing, and features of downstream control structures. The analysis methods are applied to two cases of emergency closure of power generating stations in Quebec. The results of calculated air demand and pressure drop are in good comparison with field measurements. Emergency closure is shown to produce two significant impacts on penstocks and air vents: 1) intensified water jet in the first half of the time period it takes to close the gate; and 2) pressure drop in the last one third of the time period. Air entrainment by high-velocity flowing water is an important cause of pressure drop in emergency closure, and can be modeled using hydraulic jump entrainment equations. The values of air pressure drop calculated for the Isle-Maligne and La Tuque stations are below one third of the standard atmospheric pressure. However, there are significant air pressure fluctuations. This study has contributed to the development of quantitative framework and calculation procedures that can easily be extended for applications to other sites. The development is of engineering relevance to upgrade of existing air vents and the design of new air vents and to safe operations of emergency closure

Measurement of the B0s→μ+μ− Branching Fraction and Effective Lifetime and Search for B0→μ+μ− Decays

A search for the rare decays Bs0→μ+μ- and B0→μ+μ- is performed at the LHCb experiment using data collected in pp collisions corresponding to a total integrated luminosity of 4.4  fb-1. An excess of Bs0→μ+μ- decays is observed with a significance of 7.8 standard deviations, representing the first observation of this decay in a single experiment. The branching fraction is measured to be B(Bs0→μ+μ-)=(3.0±0.6-0.2+0.3)×10-9, where the first uncertainty is statistical and the second systematic. The first measurement of the Bs0→μ+μ- effective lifetime, τ(Bs0→μ+μ-)=2.04±0.44±0.05  ps, is reported. No significant excess of B0→μ+μ- decays is found, and a 95% confidence level upper limit, B(B0→μ+μ-)<3.4×10-10, is determined. All results are in agreement with the standard model expectations.A search for the rare decays $B^0_s\to\mu^+\mu^-$ and $B^0\to\mu^+\mu^-$ is performed at the LHCb experiment using data collected in $pp$ collisions corresponding to a total integrated luminosity of 4.4 fb$^{-1}$. An excess of $B^0_s\to\mu^+\mu^-$ decays is observed with a significance of 7.8 standard deviations, representing the first observation of this decay in a single experiment. The branching fraction is measured to be ${\cal B}(B^0_s\to\mu^+\mu^-)=\left(3.0\pm 0.6^{+0.3}_{-0.2}\right)\times 10^{-9}$, where the first uncertainty is statistical and the second systematic. The first measurement of the $B^0_s\to\mu^+\mu^-$ effective lifetime, $\tau(B^0_s\to\mu^+\mu^-)=2.04\pm 0.44\pm 0.05$ ps, is reported. No significant excess of $B^0\to\mu^+\mu^-$ decays is found and a 95 % confidence level upper limit, ${\cal B}(B^0\to\mu^+\mu^-)<3.4\times 10^{-10}$, is determined. All results are in agreement with the Standard Model expectations

Air Pressure Drop in a Penstock during the Course of Intake-Gate Closure

In urgent situations, the intake gates of a hydroelectric power generating station must be closed to stop the inflow of water to the stationâ s penstock. During the course of gate closure, the air pressure in the penstock can drop drastically, posing safety risks. This paper aims to develop reliable methods for predicting pressure drop. The methods consider time-dependent water inflow, air entrainment in the penstock, air-water outflow from the penstock, and airflow down the air vent system. The methods are used to calculate time-dependent flow and pressure drop for two stations in Quebec, producing results in good comparison with field measurements. In the penstock, water jet intensifies in the first half of the closure time period, whereas air pressure drops in the last one third of the time period. Air entrainment is an important cause of pressure drop. The methods are useful for planning air-vent upgrades and safe closure operations.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

La barricade

L'histoire de la barricade se heurte, à un réseau de tensions ou, plutôt, de proximités inattendues qui accentuent le mystère de cette histoire sainte et sanglante. La pensée sauvage s'y combine à la science, la barbarie au rêve d'humanité, l'élan des coeurs à l'attente immobile, la surabondance au vide, le fracas au silence. L'espoir d'avènement et l'attente de la mort s'y disent, simultanément. Derrière la barricade, il n'est, souvent, pas d'autre alternative que le triomphe ou la mort. La fête, ici, précède de peu l'immolation ; le rêve se mêle vite de désespoir. Le caractère éphémère du combat s'accorde, paradoxalement, à la profondeur de la mémoire ; et l'on pourrait croire, parfois, que la lutte menée n'a guère d'autre visée que la construction du socle sur lequel pourront se fonder les futurs combats. La barricade, jusqu'au milieu du xxe siècle tout au moins, n'a cessé de diviser, de révéler, de définir et d'accentuer les antagonismes. Pour les uns, elle est le lieu du sacrifice, le légitime prélude à la paix civile et à la réalisation du rêve ; pour les autres, elle évoque le paroxysme du désordre des objets et des hommes, le pire théâtre de la violence et de la saturnale. Pour les uns, elle prélude au sacrifice nécessaire ; pour les autres au massacre nécessaire. Pour tous, elle a pour enjeu profond la fondation d'un ordre

Les immortels du Sénat, 1875-1918

Ce livre s’inscrit clans la série des recherches suscitées par l’enquête sur le personnel parlementaire de la Troisième République, entreprise par l’URA 1016 du CNRS, au sein du Centre d’histoire du xixe siècle qui asso­cie les Universités de Paris I et de Paris IV. Cet ouvrage porte sur une catégorie de sénateurs aujourd’hui oubliée : les inamovibles, nommés d’abord par l’Assemblée nationale, puis par le Sénat, conformément à la loi constitutionnelle du 24 février 1875. Jusqu’à la révision constitutionnelle de 1884, qui mit fin à ce mode de désignation, il y eut cent seize sénateurs inamovibles. Les diverses contributions réunies dans la première partie apportent des éléments de réflexion sur les origines sociales et la formation, les alliances et réseaux familiaux, les attitudes philosophiques et spirituelles, les liens avec le monde militaire, le barreau, le monde académique. Il fallait évo­quer leur enracinement provincial, leur place dans les conseils du gouver­nement, leur comportement politique grâce à quelques scrutins qui per­mettent au reste de décrire tendances et groupes dans le Sénat des débuts de la République. Enfin, les obsèques des sénateurs inamovibles et la mémoire qui les accompagne constituent comme le tombeau de ces « immortels » de la République. Les profils biographiques présentés ensuite trouveront sûrement l’attention de tous ceux qui s’intéressent aux élites socio-politiques de la France contemporaine. On découvre nombre de personnalités dont les débuts, non seulement professionnels mais politiques, datent de la monar­chie de Juillet, voire de la fin de la Restauration. Certaines de leurs exis­tences. et pas seulement celles des officiers de l’armée de terre ou de marine, sont marquées au coin du romanesque. Elles font revivre, comme en un éclair, l’histoire mouvementée de la France du xixe siècle, jalonnée par les révolutions, les changements de régime, les choix difficiles entre fidélité et ralliement. Ce livre éclaire une institution rarement étudiée et un personnel mal connu, qui doit tant à la France des notables, une France de propriétaires et de juristes, attachée au libéralisme

Search for the decays Bs0→τ+τ−B_s^0\to\tau^+\tau^- and B0→τ+τ−B^0\to\tau^+\tau^-

A search for the rare decays $B_s^0\to\tau^+\tau^-$ and $B^0\to\tau^+\tau^-$ is performed using proton$-$proton collision data collected with the LHCb detector. The data sample corresponds to an integrated luminosity of 3fb$^{-1}$ collected in 2011 and 2012. The $\tau$ leptons are reconstructed through the decay $\tau^-\to\pi^-\pi^+\pi^-\nu_{\tau}$. Assuming no contribution from $B^0\to\tau^+\tau^-$ decays, an upper limit is set on the branching fraction $\mathcal{B}(B_s^0\to\tau^+\tau^-) < 6.8\times 10^{-3}$ at 95% confidence level. If instead no contribution from $B_s^0\to\tau^+\tau^-$ decays is assumed, the limit is $\mathcal{B}(B^0\to\tau^+\tau^-)< 2.1 \times 10^{-3}$ at 95% confidence level. These results correspond to the first direct limit on $\mathcal{B}(B_s^0\to\tau^+\tau^-)$ and the world's best limit on $\mathcal{B}(B^0\to\tau^+\tau^-)$.A search for the rare decays Bs0→τ+τ- and B0→τ+τ- is performed using proton–proton collision data collected with the LHCb detector. The data sample corresponds to an integrated luminosity of 3  fb-1 collected in 2011 and 2012. The τ leptons are reconstructed through the decay τ-→π-π+π-ντ. Assuming no contribution from B0→τ+τ- decays, an upper limit is set on the branching fraction B(Bs0→τ+τ-)<6.8×10-3 at the 95% confidence level. If instead no contribution from Bs0→τ+τ- decays is assumed, the limit is B(B0→τ+τ-)<2.1×10-3 at the 95% confidence level. These results correspond to the first direct limit on B(Bs0→τ+τ-) and the world’s best limit on B(B0→τ+τ-).A search for the rare decays $B_s^0\to\tau^+\tau^-$ and $B^0\to\tau^+\tau^-$ is performed using proton--proton collision data collected with the LHCb detector. The data sample corresponds to an integrated luminosity of 3fb$^{-1}$ collected in 2011 and 2012. The $\tau$ leptons are reconstructed through the decay $\tau^-\to\pi^-\pi^+\pi^-\nu_{\tau}$. Assuming no contribution from $B^0\to\tau^+\tau^-$ decays, an upper limit is set on the branching fraction $\mathcal{B}(B_s^0\to\tau^+\tau^-) < 6.8\times 10^{-3}$ at 95% confidence level. If instead no contribution from $B_s^0\to\tau^+\tau^-$ decays is assumed, the limit is $\mathcal{B}(B^0\to\tau^+\tau^-)< 2.1 \times 10^{-3}$ at 95% confidence level. These results correspond to the first direct limit on $\mathcal{B}(B_s^0\to\tau^+\tau^-)$ and the world's best limit on $\mathcal{B}(B^0\to\tau^+\tau^-)$

Observation of five new narrow Ωc0\Omega_c^0 states decaying to Ξc+K−\Xi^+_c K^-

The $\Xi^+_c K^-$ mass spectrum is studied with a sample of $pp$ collision data corresponding to an integrated luminosity of 3.3 fb$^{-1}$, collected by the LHCb experiment. The $\Xi^+_c$ is reconstructed in the decay mode $pK^- \pi^+$. Five new, narrow excited $\Omega_c^0$ states are observed: the $\Omega_c (3000)^0$, $\Omega_c (3050)^0$, $\Omega_c (3066)^0$, $\Omega_c (3090)^0$, and $\Omega_c (3119)^0$. Measurements of their masses and widths are reported.The Ξc+K- mass spectrum is studied with a sample of pp collision data corresponding to an integrated luminosity of 3.3  fb-1, collected by the LHCb experiment. The Ξc+ is reconstructed in the decay mode pK-π+. Five new, narrow excited Ωc0 states are observed: the Ωc(3000)0, Ωc(3050)0, Ωc(3066)0, Ωc(3090)0, and Ωc(3119)0. Measurements of their masses and widths are reported.The $\Xi_c^+ K^-$ mass spectrum is studied with a sample of $pp$ collision data corresponding to an integrated luminosity of 3.3 fb$^{-1}$, collected by the LHCb experiment. The $\Xi_c^+$ is reconstructed in the decay mode $p K^- \pi^+$. Five new, narrow excited $\Omega_c^0$ states are observed: the $\Omega_c(3000)^0$, $\Omega_c(3050)^0$, $\Omega_c(3066)^0$, $\Omega_c(3090)^0$, and $\Omega_c(3119)^0$. Measurements of their masses and widths are reported

Measurement of the inelastic pppp cross-section at a centre-of-mass energy of 13 TeV

The cross-section for inelastic proton-proton collisions at a centre-of-mass energy of 13 TeV is measured with the LHCb detector. The fiducial cross-section for inelastic interactions producing at least one prompt long-lived charged particle with momentum p > 2 GeV/c in the pseudorapidity range 2 < η < 5 is determined to be σ$_{acc}$ = 62.2 ± 0.2 ± 2.5 mb. The first uncertainty is the intrinsic systematic uncertainty of the measurement, the second is due to the uncertainty on the integrated luminosity. The statistical uncertainty is negligible. Extrapolation to full phase space yields the total inelastic proton-proton cross-section σ$_{inel}$ = 75.4 ± 3.0 ± 4.5 mb, where the first uncertainty is experimental and the second due to the extrapolation. An updated value of the inelastic cross-section at a centre-of-mass energy of 7 TeV is also reported

Measurement of C ⁣PC\!P asymmetries in two-body B(s)0B_{(s)}^{0}-meson decays to charged pions and kaons

International audienceThe time-dependent CP asymmetries in B0→π+π- and Bs0→K+K- decays are measured using a data sample of p p collisions corresponding to an integrated luminosity of 3.0  fb-1, collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV. The same data sample is used to measure the time-integrated CP asymmetries in B0→K+π- and Bs0→π+K- decays. The results are Cπ+π-=-0.34±0.06±0.01, Sπ+π-=-0.63±0.05±0.01, CK+K-=0.20±0.06±0.02, SK+K-=0.18±0.06±0.02, AK+K-ΔΓ=-0.79±0.07±0.10, ACPB0=-0.084±0.004±0.003, and ACPBs0=0.213±0.015±0.007, where the first uncertainties are statistical and the second systematic. Evidence for CP violation is found in the Bs0→K+K- decay for the first time