53,162 research outputs found
A two-parameter wind speed algorithm for Ku-band altimeters
Full text linkGlobally distributed crossovers of altimeter and scatterometer observations clearly demonstrate that ocean altimeter backscatter correlates with both the near-surface wind speed and the sea state. Satellite data from TOPEX/Poseidon and NSCAT are used to develop an empirical altimeter wind speed model that attenuates the sea-state signature and improves upon the present operational altimeter wind model. The inversion is defined using a multilayer perceptron neural network with altimeter-derived backscatter and significant wave height as inputs. Comparisons between this new model and past single input routines indicates that the rms wind error is reduced by 10%–15% in tandem with the lowering of wind error residuals dependent on the sea state. Both model intercomparison and validation of the new routine are detailed, including the use of large independent data compilations that include the SeaWinds and ERS scatterometers, ECMWF wind fields, and buoy measurements. The model provides consistent improvement against these varied sources with a wind-independent bias below 0.3 m s?1. The continuous form of the defined function, along with the global data used in its derivation, suggest an algorithm suitable for operational application to Ku-band altimeters. Further model improvement through wave height inclusion is limited due to an inherent multivaluedness between any single realization of the altimeter measurement pair [?o, HS] and observed near-surface winds. This ambiguity indicates that HS is a limited proxy for variable gravity wave properties that impact upon altimeter backscatter
Jason-1/Jason-2 metocean comparisons and monitoring
Full text linkThe initial tandem phase of the Jason-2 mission is important for the calibration of the entire altimetric system, not just the records of sea surface height. However, as well as allowing a bulk comparison of metocean parameters such as wave height and backscatter strength (used to infer wind speed), it affords a more detailed opportunity to understand the artefacts within each instrument. The wave height comparison shows no bias between the instruments, with the mismatch error of consecutive points independent of one another. The backscatter difference is not a simple offset, but has a trend with weak non-linear variations. The technique for backscatter monitoring using Ku-/C-band differences is validated during the tandem phase, and extended to show ~59-day oscillations throughout the Jason-1 mission. This effect, which is predominantly in the C-band, is related to changing solar exposure, due to the fraction of orbit in eclipse varying as the orbit precesses. Such anomalies were partially present in TOPEX-B data, but are not noticeable for Jason-2. It is recommended that all TOPEX, Jason-1 and Jason-2 data be transformed to a consistent scale, allowing for the bias and trend terms in the offsets between instruments, and correcting for any long-period drifts in individual calibration; this will enable a single wind speed algorithm to be applied to the combined satellite data
Evidence for the decay B0→J/ψω and measurement of the relative branching fractions of meson decays to J/ψη and J/ψη′
Full text linkFirst evidence of the B 0 → J / ψ ω decay is found and the B s 0 → J / ψ η and B s 0 → J / ψ η ′ decays are studied using a dataset corresponding to an integrated luminosity of 1.0 fb -1 collected by the LHCb experiment in proton-proton collisions at a centre-of-mass energy of sqrt(s) = 7 TeV. The branching fractions of these decays are measured relative to that of the B 0 → J / ψ ρ 0 decay:frac(B (B 0 → J / ψ ω), B (B 0 → J / ψ ρ 0)) = 0.89 ± 0.19 (stat) - 0.13 + 0.07 (syst),frac(B (B s 0 → J / ψ η), B (B 0 → J / ψ ρ 0)) = 14.0 ± 1.2 (stat) - 1.5 + 1.1 (syst) - 1.0 + 1.1 (frac(f d, f s)),frac(B (B s 0 → J / ψ η ′), B (B 0 → J / ψ ρ 0)) = 12.7 ± 1.1 (stat) - 1.3 + 0.5 (syst) - 0.9 + 1.0 (frac(f d, f s)), where the last uncertainty is due to the knowledge of f d / f s, the ratio of b-quark hadronization factors that accounts for the different production rate of B 0 and B s 0 mesons. The ratio of the branching fractions of B s 0 → J / ψ η ′ and B s 0 → J / ψ η decays is measured to befrac(B (B s 0 → J / ψ η ′), B (B s 0 → J / ψ η)) = 0.90 ± 0.09 (stat) - 0.02 + 0.06 (syst)
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Measurement of the B0–B0 oscillation frequency Δmd with the decays B0→D−π+ and B0→ J/ψK∗0
Full text linkThe B
0
–B
0
oscillation frequency Δmd is measured by the LHCb experiment using a dataset corresponding
to an integrated luminosity of 1.0 fb−1
of proton–proton collisions at √
s = 7 TeV, and is found to be
Δmd
=0.5156±0.0051 (stat.)±0.0033 (syst.) ps−1
. The measurement is based on results from analyses
of the decays B
0
→ D
−π
+ (D
−
→ K
+π
−π
−) and B
0
→ J/ψK
∗0
(J/ψ →μ
+μ
−,K
∗0
→ K
+π
−) and
their charge conjugated modes
Measurement of the ratio of branching fractions B(B0→K∗0γ )/B(B0s→φγ ) and the directCP asymmetry inB 0→K∗0γ
Full text linkThe ratio of branching fractions of the radiative B decays B0→K⁎0γ and B0s→ϕγ has been measured using an integrated luminosity of 1.0 fb−1 of pp collision data collected by the LHCb experiment at a centre-of-mass energy of s√=7TeV. The value obtained is
B(B0→K⁎0γ)B(B0s→ϕγ)=1.23±0.06(stat.)±0.04(syst.)±0.10(fs/fd),
where the first uncertainty is statistical, the second is the experimental systematic uncertainty and the third is associated with the ratio of fragmentation fractions fs/fd. Using the world average value for B(B0→K⁎0γ), the branching fraction B(B0s→ϕγ) is measured to be (3.5±0.4)×10−5.
The direct CP asymmetry in B0→K⁎0γ decays has also been measured with the same data and found to be
ACP(B0→K⁎0γ)=(0.8±1.7(stat.)±0.9(syst.))%.
Both measurements are the most precise to date and are in agreement with the previous experimental results and theoretical expectations
Measurement of CP observables in B-+/- -> D(*)K-+/- and B-+/- -> D(*)pi(+/-) decays
Full text linkMeasurements of CP observables in B-+/- -> D(*)K-+/- and B-+/- -> D(*)pi(+/-) decays are presented, where D(*) indicates a neutral Dor D* meson that is an admixture of D(*)(0) and (D) over bar(*)(0) states. Decays of the D* meson to the D pi(0)and D gamma final states are partially reconstructed without inclusion of the neutral pion or photon, resulting in distinctive shapes in the Bcandidate invariant mass distribution. Decays of the D meson are fully reconstructed in the K-+/-pi(-/+), K+K- and pi(+)pi(-) final states. The analysis uses a sample of charged Bmesons produced in ppcollisions collected by the LHCb experiment, corresponding to an integrated luminosity of 2.0, 1.0 and 2.0fb- 1taken at centre- of- mass energies of root s = 7, 8 and 13 TeV, respectively. The study of B-perpendicular to -> D*K-perpendicular to and B-perpendicular to -> D*pi(perpendicular to) decays using a partial reconstruction method is the first of its kind, while the measurement of B-+/- -> DK +/- and B-+/- -> D pi(+/-) decays is an update of previous LHCb measurements. The B-+/- -> DK +/- results are the most precise to date. (c) 2017 The Author. Published by Elsevier B. V
Viscosity data for hydrous peraluminous granitic melts: comparison with a metaluminous model
No full textWe performed 27 viscosity determinations on dry and water-bearing peraluminous haplogranitic melts. The dry melt compositions cover the range of normative corundum to be expected in peraluminous granitic melts in nature. The compositions are based on addition
of Al2O3 to a haplogranitic melt (HPG8) whose composition is near that of the projection
of the 2 kbar H2O-saturated minimum melt composition into the system NaAlSi3O8-
KAlSi3O8-SiO2. The H2O contents of the hydrous melts were analyzed using Karl Fischer titration ranging from 1 to 3 wt%. The viscosity determinations were performed using a
modified micropenetration method in the viscosity range of 1010 to 1011 Pa·s, at 1 atm
pressure, and in the temperature ranges of 880–940 °C and 470–640 °C for the dry and wet melts, respectively. For the dry peraluminous melts in this high viscosity range, addition of the first few percent of normative corundum to a metaluminous granitic melt increases the viscosity, which remains nearly constant despite further addition of Al2O3.
Thus a viscosity maximum is inferred for dry slightly peraluminous granitic melts. The hydrous melt viscosity data were compared with the recent calculational model of Hess and Dingwell (1996), which was based on and designed for metaluminous melt viscosities.
That model is capable of describing the viscosities of hydrous peraluminous granitic melts within the uncertainties stated for its application in metaluminous melts
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Inclusive decays B->DX and B->D*X
Full text linkComplete Author List: Gibbons L, Johnson SD, Kwon Y, Roberts S, Thorndike EH, Jessop CP, Lingel K, Marsiske H, Perl ML, Schaffner SF, Ugolini D, Wang R, Zhou X, Coan TE, Fadeyev V, Korolkov I, Maravin Y, Narsky I, Shelkov V, Staeck J, Stroynowski R, Volobouev I, Ye J, Artuso M, Efimov A, Frasconi F, Gao M, Goldberg M, He D, Kopp S, Horwitz N, Moneti GC, Mountain R, Mukhin Y, Schuh S, Skwarnicki T, Stone S, Thulasidas M, Viehhauser G, Xing X, Bartelt J, Csorna SE, Jain V, Marka S, Freyberger A, Godang R, Kinoshita K, Lai IC, Pomianowski P, Schrenk S, Bonvicini G, Cinabro D, Greene R, Perera LP, Barish B, Chadha M, Chan S, Eigen G, Miller JS, OGrady C, Schmidtler M, Urheim J, Weinstein AJ, Wurthwein F, Asner DM, Bliss DW, Brower WS, Masek G, Paar HP, Sharma V, Gronberg J, Kutschke R, Lange DJ, Menary S, Morrison RJ, Nelson HN, Nelson TK, Qiao C, Richman JD, Roberts D, Ryd A, Witherell MS, Balest R, Behrens BH, Cho K, Ford WT, Park H, Rankin P, Roy J, Smith JG, Alexander JP, Bebek C, Berger BE, Berkelman K, Bloom K, Cassel DG, Cho HA, Coffman DM, Crowcroft DS, Dickson M, Drell PS, Ecklund KM, Ehrlich R, Elia R, Foland AD, Gaidarev P, Gittelman B, Gray SW, Hartill DL, Heltsley BK, Kandaswamy J, Katayama N, Kim PC, Kreinick DL, Lee T, Liu Y, Ludwig GS, Masui J, Mevissen J, Mistry NB, Ng CR, Nordberg E, Ogg M, Patterson JR, Peterson D, Riley D, Soffer A, Ward C, Athanas M, Avery P, Jones CD, Lohner M, Prescott C, Yang S, Yelton J, Zheng J, Brandenburg G, Briere RA, Gao YS, Kim DYJ, Wilson R, Yamamoto H, Browder TE, Li F, Li Y, Rodriguez JL, Bergfeld T, Eisenstein BI, Ernst J, Gladding GE, Gollin GD, Hans RM, Johnson E, Karliner I, Marsh MA, Palmer M, Selen M, Thaler JJ, Edwards KW, Bellerive A, Janicek R, MacFarlane DB, McLean KW, Patel PM, Sadoff AJ, Ammar R, Baringer P, Bean A, Besson D, Coppage D, Darling C, Davis R, Hancock N, Kotov S, Kravchenko I, Kwak N, Anderson S, Kubota Y, Lattery M, ONeill JJ, Patton S, Poling R, Riehle T, Savinov V, Smith A, Alam MS, Athar SB, Ling Z, Mahmood AH, Severini H, Timm S, Wappler F, Anastassov A, Blinov S, Duboscq JE, Fisher KD, Fujino D, Fulton R, Gan KK, Hart T, Honscheid K, Kagan H, Kass R, Lee J, Spencer MB, Sung M, Undrus A, Wanke R, Wolf A, Zoeller MM, Nemati B, Richichi SJ, Ross WR, Skubic P, Wood M, Bishai M, Fast J, Gerndt E, Hinson JW, Menon N, Miller DH, Shibata EI, Shipsey IPJ, Yurko M</p
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