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71.
Several glasses synthesized by sol–gel route and based on the BaO–B2O3–X–Al2O3–SiO2 (X = CaO, MgO) glass system have been investigated to evaluate their applicability as sealant for solid oxide fuel cell (SOFC). Chemical interactions with K41X stainless steel and hydrogen‐tightness of these materials were evaluated after operations at high temperatures over 1,000 h in air atmosphere. Formation of a new phase at the steel–glass interface and formation of porosity in the glass were observed and determined as critical problems over mid‐term operations. The role of MgO is important to obtain a gas‐tight sealing. Application of the glass paste without binder addition was performed in order to avoid possible residual porosity related problems. The best glass was finally used as sealant between anodic and cathodic compartments in complete SOFCs operated at 760 and at 800 °C. Open circuit voltages and power densities of the cells were recorded during the first hours of operation. 相似文献
72.
S. Fvrier D. Gaponov M. Devautour P. Roy L. Daniault M. Hanna D.N. Papadopoulos F. Druon P. Georges M.E. Likhachev M.Y. Salganskii M.V. Yashkov 《Optical Fiber Technology》2010,16(6):419-427
In the search for ever higher output power or energy from fibre oscillators or amplifiers a nowadays mature technology relies on enlarging the fibre mode area. Broadening of the core diameter, all other things being equal, inevitably yields a multimode fibre, thereby dramatically limiting the device usefulness. Various strategies have been deployed to design and manufacture single transverse mode fibre oscillators and amplifiers, among which making use of the so-called photonic bandgap effect to restrict the modal population seems promising. Helped by efficient and reliable numerical tools the design of large mode area singlemode photonic bandgap fibres is presented. Two fibres with 20-μm and 40-μm core diameter, both of them heavily doped with Yb3+ ions, have been fabricated by the widespread modified chemical vapour deposition process and are shown to behave properly when used as the core element of either continuous wave oscillators or femtosecond amplifiers. Good output beam quality (M2 parameter spanning from 1.12 to 1.5 for the set of fibres studied) and high slope efficiency of 80% in cw oscillation regime are demonstrated. Furthermore the 40-μm core diameter fibre is shown to be resilient to tight bending down to 7.5-cm radius. The stack-and-draw process makes it easy to tailor the outer cladding so that a large numerical aperture can be reached. Subsequently, from this air-clad fibre, 500 fs 47 W pulses at 35 MHz are obtained from a two-stage chirped pulse amplification system. 相似文献
73.
74.
Douay M. Feng T. Bernage P. Niay P. Delevaque E. Georges T. 《Photonics Technology Letters, IEEE》1992,4(8):844-846
The spectra of Nd3+- and Pr3+-doped fibre lasers utilizing an intracore Bragg grating reflector written at 1.08-μm Bragg wavelength and a dichroic mirror for cavity feedback have been investigated under 0.6-GHz resolution. Two oscillating frequencies corresponding to two orthogonal linear polarization states of laser emission were observed. The frequencies and orientations of the two linearly polarized emissions could be changed by varying the fiber birefringence with an inline polarization controller. A phenomenological model is proposed to explain the experimental results 相似文献
75.
A. Bouchier G. Lucas-Leclin F. Balembois P. Georges 《Photonics Technology Letters, IEEE》2004,16(9):2021-2023
We present an amplified spontaneous emission (ASE) source based on a single-mode ytterbium-doped fiber pumped by a Nd : YVO/sub 4/ laser emitting at 914 nm. The ASE is centered on 977 nm with a bandwidth of 3 nm. With a spectrally filtered reflection of the copropagating ASE, we have obtained a source of ASE with a bandwidth of 0.4 nm and a tunability of 7 nm. This source delivers an output power of 340 for 700 mW of pump power, with a slope efficiency of 50%. 相似文献
76.
B Georges L Brown M Mazerolles JF Decun P Cougot M Archambaud C Suc P Andrieu C Virenque 《Canadian Metallurgical Quarterly》1997,26(11):502-506
OBJECTIVES: To evaluate the development of resistance to fosfomycin or fucidic acid in severe infections caused by methicillin-resistant Staphylococcus aureus (MRSA) and to assess the relationship with serum levels of vancomycin METHODS: A retrospective study was performed in patients hospitalized in our intensive care unit during a 3-year period (1993-1995) who were treated for severe MRSA infection with continuous infusion vacomycin and fosfomycin or fucidic acid. We analyzed the development of resistance and serum levels of vancomycin. RESULTS: During this period, only 20 patients received continuous infusion vancomycin plus fucidic acid or fosfomycin. MSRA resistant to fucidic or fosfomycin developed in 9. Vancomycin serum levels were significantly lower in patients who developed resistance to focidic acid or fosfomycin, both during the first 5 days of treatment (16.68 +/- 1.07 micrograms/ml vs. 22.64 +/- 1.05 mg/ml, p < 0.01) and throughout treatment duration (17.29 +/- 1.07 micrograms/ml vs. 21.85 +/- 0.78 microgram/ml, p < 0.01). CONCLUSIONS: Our findings confirm that in spite of continuous vancomycin infusion at an initial rate of 2 g/24 h, Staphylococcus aureus resistance to fosfomycin or fucidic acid an develop during ongoing treatment. Vancomycin levels of at least 20 micrograms/ml should be obtained as rapidly as possible. 相似文献
77.
78.
79.
Laurent Cormier Daniel R. Neuville Georges Calas 《Journal of the American Ceramic Society》2005,88(8):2292-2299
The anomalous behavior of the glass transition temperature ( T g ) in low silica calcium aluminosilicate glasses has been related to the structural modifications observed by neutron and X-ray diffraction. The diffraction data indicate that Al and Si are in tetrahedral sites and that Ca atoms are in distorted octahedral sites. By subtracting the correlation functions for glasses at constant SiO2 or constant Al2 O3 content, we have shown that Si and Al atoms are introduced in a different way within the glass structure. Si is present in various Q n sites, while Al resides in Q3 and Q4 sites for glasses with high CaO content and enters fully polymerized Q4 sites with increasing SiO2 or Al2 O3 content. The higher proportion of Al in Q3 positions at high CaO content yields a depolymerization of the network. The lower connectivity will contribute to a decrease of the viscosity, which may be at the origin of the decrease of T g for glasses at low silica content. 相似文献
80.
Delphine Antoni Jean-Baptiste Clavier Marius Pop Catherine Schumacher Fran?ois Lefebvre Georges No?l 《International journal of molecular sciences》2014,15(5):7554-7562