Extension of Lyman-alpha Complexes from HST Observations of Four Pairs of Quasars

in Combes, F.; Barret, D. (Eds.) SF2A-2002: Semaine de l'Astrophysique Francaise (2002, June 01)

We present HST observations of four pairs of quasars with 2,3 arcmin angular separation and redshift z 0.9. We apply the Nearest-Neighbor method to the sample of observed Lyman-alpha lines with rest ... [more ▼]

We present HST observations of four pairs of quasars with 2,3 arcmin angular separation and redshift z 0.9. We apply the Nearest-Neighbor method to the sample of observed Lyman-alpha lines with rest equivalent width greater than 0.3 Angstrum. According to Monte-Carlo simulations, we detect an excess of coincidences with velocity difference smaller than 500 km/s. [less ▲]

Extension of the Direct strength method to hot-rolled profiles cross-sections

in 6th European Conference on Steel and Composite Structures : Eurosteel 2011, Budapest 30 October - 2 September 2011 (2011, September)

Current metallic structural design codes use the concept of section classification for determining the section capacity of hot-rolled profiles. In this system, there exists a discontinuity between the ... [more ▼]

Current metallic structural design codes use the concept of section classification for determining the section capacity of hot-rolled profiles. In this system, there exists a discontinuity between the classes 2 and 3, while for the class 4, the effective width method (EWM) must be used to account for local buckling phenomenon. In order to overcome the complicate and time consuming EWM for evaluating the strength, the alternative Direct Strength Method (DSM) approach, developed only for cold-formed thin-walled members, has gained importance over the last few years. The DSM is premised on the assumption that the strength can be predicted from the yield strength to the elastic critical load ratio in conjunction with a strength curve. The DSM has been advanced for calculating the strength of compression members over the past decades and in this paper, the extension of DSM to hot-rolled profiles cross-sections is investigated. Firstly, the methods for calculating the cross-section resistance such as EWM, DSM, and the recent Continuous Strength Method (CSM) are reviewed; a short comparison is made and their domains of applicability are commented. Secondly, a numerical model carried out in the frame of this research is described. The model was built in ABAQUS and verified against test results of the “Semi-comp: Plastic member capacity of semi-compact steel sections - a more economic design” project, which was carried out earlier with the objective of improving the utilization of plasticity in rolled and welded sections with medium cross-section slenderness. On the basis of these premises, the final goal of the project is detailed: to derive a new formulation that would cover the whole field of section slenderness (present class 1 to class 4), which can be seen as an extension of the so-called DSM approach. [less ▲]

Extension of the experiment of J.H.C. Smith on the onset of oxygen evolution in etiolated leaves

in Brouers, Michel; Sironval, Cyrille (Eds.) Protochlorophyllide Reduction and Greening (1984)

Extension of the Liège intranuclear cascade model at incident energies between 2 and 12 GeV. Aspects of pion production.

in Nuclear Physics A (2011), 866

Extension of the long-term total column time series of atmospheric methane above the Jungfraujoch station: analysis of grating infrared spectra between 1976 and 1989

in Geophysical Research Abstracts (2011), 13

Methane (CH4) is one of the most abundant greenhouse gases in the Earth’s atmosphere, with current mean volume mixing ratio close to 1800 ppb. Since methane has a global warming potential of 25 (100-yr ... [more ▼]

Methane (CH4) is one of the most abundant greenhouse gases in the Earth’s atmosphere, with current mean volume mixing ratio close to 1800 ppb. Since methane has a global warming potential of 25 (100-yr horizon) and an atmospheric lifetime of 12 years, the Kyoto Protocol has included it among the species to be regulated to limit global warming. Anthropogenic sources of methane are mainly energy production (coal and leaks) and agriculture while main natural sources are swamps and biomass waste. The main sink of methane is oxidation in the troposphere, primarily by reaction with the hydroxyl radical. Methane trends have exhibited significant changes during the last twenty-five years. For instance, long-term monitoring of its vertical total column above the high-altitude station of the Jungfraujoch (46.5°N, 8°E, 3580 m asl) has indeed allowed to derive column changes ranging from +0.72% in 1987-1988 to +0.14% in 1999-2000 (Zander et al., 2002), relative to 1988 and 2000, respectively. More recently and for the same site, Duchatelet et al. (2010) have even reported a significant slowdown of -0.02%/yr between years 2000 and 2005. This study also showed that since then, CH4 is on the rise again, at a rate close to +0.30%/yr. While the numbers reported here above have been derived from the Fourier Transform Infrared (FTIR) data set starting in 1984, earlier pioneering observations have been collected at the Jungfraujoch since 1950, using grating spectrometers. During the 1958-1975 period, the main objectives has been the study of the solar photosphere in the visible and the near infrared and the publication of high-resolution solar atlases. From 1976 to 1989, narrow-band IR solar absorption observations achieving a spectral resolution of about 0.02 cm-1 have been recorded with the high-performance double-pass grating spectrometer. Analysis of these historical spectra provides a unique opportunity to extend the Jungfraujoch’s total column time series of important atmospheric gases, including methane, by nearly 10 years. The aim of this contribution is to present the inversion strategy adopted to derive CH4 from the grating spectra, using the SFIT-2 algorithm (v3.91) We will evaluate the impact of resolution, spectroscopic parameters (from the EU HYMN project -see www.knmi.nl/samen/hymn-, and from HITRAN 2004), atmospheric pressure and temperature profiles on the error budget. The 1976-1989 total column time series produced will be presented and critically discussed. In particular, we will identify and correct for possible biases between double-pass grating spectrometer measurements and more recent FTIR total columns. The harmonized and consolidated time series will be investigated to characterize the long-term trend of methane for the 1976-2010 time period. Comparisons with synthetic data produced by the CHASER 3-dimensional chemical transport model will also be presented and analyzed. [less ▲]

Extension of the Marchenko equation to non-Hermitian differential systems

in Annals of Physics (1980), 126(2), 460--499

An extension of the radial return algorithm to account for rate-dependent effects in frictional contact and visco-plasticity

in Journal of Materials Processing Technology (1998), 80-1

This paper deals with unified elasto-plastic and elastic-visco-plastic constitutive equations for metals submitted to large deformations. We present here a newly developed time integration algorithm which ... [more ▼]

This paper deals with unified elasto-plastic and elastic-visco-plastic constitutive equations for metals submitted to large deformations. We present here a newly developed time integration algorithm which is an extension to the visco-plastic range of the classical radial return algorithm for plasticity. The resulting implicit algorithm is both efficient and very inexpensive. This algorithm is also subsequently extended to frictional problems where it allows a generalisation of the classical Coulomb dry friction criterion to a criterion depending on the relative slip velocity such as those encountered in the hydrodynamic regime. (C) 1998 Elsevier Science S.A. All rights reserved. [less ▲]

An extension of the Radial Return Scheme for Springback Similation in Sheet Metal Forming

in 6th ICTP-International Conference on Technology of Plasticity, Nuremberg (1999)

Extensions and applications of a mid-term voltage stability analysis method

in Proc. 3rd Intern. Workshop on Bulk Power system voltage phenomena : voltage stability and security (1994, August)

Extensions and restrictions of Wythoff's game preserving its P-positions

Scientific conference (2011, October 21)

Wythoff's game is a century old classical two players combinatorial game. When studying this game, Beatty sequences associated with the Golden Ratio, syntactical properties of the representations of ... [more ▼]

Wythoff's game is a century old classical two players combinatorial game. When studying this game, Beatty sequences associated with the Golden Ratio, syntactical properties of the representations of integers in the Fibonacci or Zeckendorf numeration system and the morphic Fibonacci word appear naturally in characterizations of its P-positions. Recall that whatever is the move played from a P-position, the other player has a winning strategy. Contrarily to the usual approach where one defines a new game by a set of rules and then tries to characterize the corresponding set of P-positions, our motivations are to proceed the other way around: keep the original set of P-positons while changing the rules. We consider extensions and restrictions of Wythoff's game having exactly the same set of P-positions as the original game. Our results are the following one: no strict subset of rules gives the same set of P-positions. On the other hand, we characterize all moves that can be adjoined while preserving the original set of P-positions. Testing if a move belongs to such an extended set of rules is shown to be done in polynomial time. In this talk, we won't consider many game theoretical aspects (but we will recall some basic facts on combinatorial games). We focus mainly on the role played by numeration systems, regular languages and bidimensional words generated by substitutions/morphisms. Indeed, games like this one provide nice interaction between combinatorics on words and combinatorial game theory. For instance, the set of P-positions of Wythoff's game are "coded" by the infinite Fibonacci word. Therefore, many arguments rely on this word, on automatic sequences and on the corresponding numeration systems. With these tools, we provide new bidimensional (shape-symmetric in the sense of Arnaud Maes) morphisms generating an infinite picture encoding respectively P-positions of Wythoff's game and moves that can be adjoined preserving the same set of P-positions. [less ▲]