Optimal Operation of the Multireservoir System in the Seine River Basin Using Deterministic and Ensemble Forecasts

International audienceThis article investigates the improvement of the operation of a four-reservoir system in the Seine River basin, France, by use of deterministic and ensemble weather forecasts and real-time control. In the current management, each reservoir is operated independently from the others and following prescribed rule-curves, designed to reduce floods and sustain low flows under the historical hydrological conditions. However, this management system is inefficient when inflows are significantly different from their seasonal average and may become even more inadequate to cope with the predicted increase in extreme events induced by climate change. In this work, a centralized real-time control system is developed to improve reservoirs operation by exploiting numerical weather forecasts that are becoming increasingly available. The proposed management system implements a well-established optimization technique, model predictive control (MPC), and its recently modified version that can incorporate uncertainties, tree-based model predictive control (TB-MPC), to account for deterministic and ensemble forecasts respectively. The management system is assessed by simulation over historical events and compared to the no-forecasts strategy based on rule-curves. Simulation results show that the proposed real-time control system largely outperforms the no-forecasts management strategy, and that explicitly considering forecast uncertainty through ensembles can compensate for the loss in performance due to forecast inaccuracy

Measurement of the Beam-Recoil Polarization in Low-Energy Virtual Compton Scattering from the Proton

Double-polarization observables in the reaction $\vec{e}p \rightarrow e'\vec{p'}\gamma{}$ have been measured at $Q^2=0.33 (GeV/c)^2$. The experiment was performed at the spectrometer setup of the A1 Collaboration using the 855 MeV polarized electron beam provided by the Mainz Microtron (MAMI) and a recoil proton polarimeter. From the double-polarization observables the structure function $P_{LT}^\perp$ is extracted for the first time, with the value $(-15.4 \pm 3.3 (stat.)^{+1.5}_{-2.4} (syst.)) GeV^{-2}$, using the low-energy theorem for Virtual Compton Sattering. This structure function provides a hitherto unmeasured linear combination of the generalized polarizabilities of the proton

Combination of two fat saturation pulses improves detectability of glucose signals in carbon-13 MR spectroscopy

In order to improve the fat suppression performance of in vivo 13C-MRS operating at 3.0 Tesla, a phantom model study was conducted using a combination of two fat suppression techniques; a set of pulses for frequency (chemical shift) selective suppression (CHESS), and spatial saturation (SAT). By optimizing the slab thickness for SAT and the irradiation bandwidth for CHESS, the signals of the –13CH3 peak at 49 ppm and the –13CH2– peak at 26 ppm simulating fat components were suppressed to 5% and 19%, respectively. Combination of these two fat suppression pulses achieved a 53% increase of the height ratio of the glucose C1β peak compared with the sum of all other peaks, indicating better sensitivity for glucose signal detection. This method will be applicable for in vivo 13C-MRS by additional adjustment with the in vivo relaxation times of the metabolites

A new measurement of the structure functions PLL−PTT/epsilonP_{LL}-P_{TT}/epsilon and PLTP_{LT} in virtual Compton scattering at Q2=Q^2= 0.33 (GeV/c)2^2

The cross section of the $ep \to e' p' \gamma$ reaction has been measured at $Q^2 = 0.33$ (GeV/c)$^2$. The experiment was performed using the electron beam of the MAMI accelerator and the standard detector setup of the A1 Collaboration. The cross section is analyzed using the low-energy theorem for virtual Compton scattering, yielding a new determination of the two structure functions P_LL}-P_{TT}/epsilon and $P_{LT}$ which are linear combinations of the generalized polarizabilities of the proton. We find somewhat larger values than in the previous investigation at the same $Q^2$. This difference, however, is purely due to our more refined analysis of the data. The results tend to confirm the non-trivial $Q^2$-evolution of the generalized polarizabilities and call for more measurements in the low-$Q^2$ region ($\le$ 1 (GeV/c)$^2$).Comment: 9 pages, 10 figures. EPJA version. slight revisions in the text and figure

Search for Relativistic Magnetic Monopoles with IceCube

We present the first results in the search for relativistic magnetic monopoles with the IceCube detector, a subsurface neutrino telescope located in the South Polar ice cap containing a volume of 1 km$^{3}$. This analysis searches data taken on the partially completed detector during 2007 when roughly 0.2 km$^{3}$ of ice was instrumented. The lack of candidate events leads to an upper limit on the flux of relativistic magnetic monopoles of \Phi_{\mathrm{90%C.L.}}\sim 3\e{-18}\fluxunits for $\beta\geq0.8$. This is a factor of 4 improvement over the previous best experimental flux limits up to a Lorentz boost $\gamma$ below $10^{7}$. This result is then interpreted for a wide range of mass and kinetic energy values.Comment: 11 pages, 11 figures. v2 is minor text edits, no changes to resul

Lateral Distribution of Muons in IceCube Cosmic Ray Events

In cosmic ray air showers, the muon lateral separation from the center of the shower is a measure of the transverse momentum that the muon parent acquired in the cosmic ray interaction. IceCube has observed cosmic ray interactions that produce muons laterally separated by up to 400 m from the shower core, a factor of 6 larger distance than previous measurements. These muons originate in high pT (> 2 GeV/c) interactions from the incident cosmic ray, or high-energy secondary interactions. The separation distribution shows a transition to a power law at large values, indicating the presence of a hard pT component that can be described by perturbative quantum chromodynamics. However, the rates and the zenith angle distributions of these events are not well reproduced with the cosmic ray models tested here, even those that include charm interactions. This discrepancy may be explained by a larger fraction of kaons and charmed particles than is currently incorporated in the simulations

Calibration and Characterization of the IceCube Photomultiplier Tube

Over 5,000 PMTs are being deployed at the South Pole to compose the IceCube neutrino observatory. Many are placed deep in the ice to detect Cherenkov light emitted by the products of high-energy neutrino interactions, and others are frozen into tanks on the surface to detect particles from atmospheric cosmic ray showers. IceCube is using the 10-inch diameter R7081-02 made by Hamamatsu Photonics. This paper describes the laboratory characterization and calibration of these PMTs before deployment. PMTs were illuminated with pulses ranging from single photons to saturation level. Parameterizations are given for the single photoelectron charge spectrum and the saturation behavior. Time resolution, late pulses and afterpulses are characterized. Because the PMTs are relatively large, the cathode sensitivity uniformity was measured. The absolute photon detection efficiency was calibrated using Rayleigh-scattered photons from a nitrogen laser. Measured characteristics are discussed in the context of their relevance to IceCube event reconstruction and simulation efforts.Comment: 40 pages, 12 figure

The IceCube Neutrino Observatory Part VI: Ice Properties, Reconstruction and Future Developments

Papers on ice properties, reconstruction and future developments submitted to the 33nd International Cosmic Ray Conference (Rio de Janeiro 2013) by the IceCube Collaboration.Comment: 28 pages, 38 figures; Papers submitted to the 33nd International Cosmic Ray Conference, Rio de Janeiro 2013; version 2 corrects errors in the author lis