A self-starting, passively mode-locked all-fibre ring laser based on the homemade Er^3＋/Yb^3＋ codoped phosphate glass fibre is reported. Dual-pump sources were used to achieve the mode-locked operation in the experi...
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A self-starting, passively mode-locked all-fibre ring laser based on the homemade Er^3＋/Yb^3＋ codoped phosphate glass fibre is reported. Dual-pump sources were used to achieve the mode-locked operation in the experiment. The fundamental mode-locked pulse repetition rate is 10.67MHz. The pulse duration, assumed as the fit of hyperbolic secant pulse shape, is 5.82ps. We also observe the multi-pulse output of the fibre laser.
Molecular dynamics simulations are performed to research the diffusion behavior of amorphous silica with hydroxyl group. Muliken analysis is employed for the determination of initial charge status of simulated systems...
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Molecular dynamics simulations are performed to research the diffusion behavior of amorphous silica with hydroxyl group. Muliken analysis is employed for the determination of initial charge status of simulated systems with various hydroxyl contents. Modified BKS potentials for the interactions between introduced hydroxyl groups and other atoms, are adopted in the present molecular dynamics simulations. Short-range atomic arrangement and self diffusion coefficients of hydroxyl-doped amorphous silica systems are calculated and hereafter compared with those of pure amorphous silica. The calculation results suggest that the doped hydroxyl groups play an important role for the mobility of atoms within the system, which can be employed to the theoretical interpretation of the oxidation process of the ceramics such as silicon nitride.
Improved genetic algorithm, combined with artificial neural network, is present for the optimal design of 2.5D braided composite. Dispersal simulation data, including maximal stresses and elastics properties, are adop...
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Improved genetic algorithm, combined with artificial neural network, is present for the optimal design of 2.5D braided composite. Dispersal simulation data, including maximal stresses and elastics properties, are adopted by artificial neural network for the calculation of strength property. Based on calculation method of strength mentioned above and other calculation models for other mechanical properties, genetic algorithm is employed for the design of structure parameters of 2.5D braided composite, such as wrap fiber density, fill fiber density and interface strength. These structure optimal parameters are finally optimized for practical application.
Amino and carboxylic groups functionalized mesoporous bioactive glasses (denoted as N-MBGs and C-MBGs, respectively) were successfully synthesized through a post-grafting process. The in vitro bioactivities testing re...
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Heat dissipation from aircraft is important. Carbon fiber polymer-matrix structural composites have high in-plane thermal conductivity, but low through-thickness conductivity. A nanostructuring method involving carbon...
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ISBN:
(纸本)9781934551042
Heat dissipation from aircraft is important. Carbon fiber polymer-matrix structural composites have high in-plane thermal conductivity, but low through-thickness conductivity. A nanostructuring method involving carbon black at the interlaminar interface was developed to improve the through thickness conductivity. Ethylene glycol monoethyl ether (EGME) was the vehicle for dispersing the carbon black and for partial dissolution of the epoxy resin on the fiber-epoxy prepreg surface. EGME evaporated from the prepreg surface prior to composite fabrication. The optimum carbon black content in EGME for attaining high through-thickness conductivity was 0.8 wt. % for both unidirectional and crossply configurations. EGME applied without carbon black improved the conductivity by up to 36%. For EGME with carbon black, the improvement was up to 210%. For the same interlaminar interface modification (except for 1.2 wt.% carbon black), the conductivity and its fractional increase were higher for the crossply configuration than the corresponding unidirectional configuration. The through-thickness compressive modulus and the flexural modulus were increased by up to 14% and 11% respectively by using EGME with carbon black. The average thickness of the interlaminar interface increased with increasing carbon black content, but it was decreased by the use of EGME alone.
Electrically conductive adherent films are useful for electrodes and microheaters. Carbon-based films of thickness ranging from 1 to 13 μm, with electrical resistivity ranging from 6.0 ×10-4 to 3 Ω.cm were prod...
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ISBN:
(纸本)9781934551042
Electrically conductive adherent films are useful for electrodes and microheaters. Carbon-based films of thickness ranging from 1 to 13 μm, with electrical resistivity ranging from 6.0 ×10-4 to 3 Ω.cm were produced on an alumina substrate, using as the carbon precursor the combination of EPON SU 2.5 epoxy (with a lower viscosity than previously used EPON SU8 epoxy) and an amine curing agent, and a carbonization temperature of 650°C. This precursor, plus solvent and/or filler(s), gave carbon films without cracks and with good edge definition, in contrast to the poor edge definition when either polyamide or amidoamine (with low amine hydrogen equivalent weights) was used instead of the amine as the curing agent. Interconnected filamentary nickel nanoparticles were more effective for conductivity enhancement than silver nanoparticles (not filamentary) at the same volume fraction (5 vol.% or below). Multiwalled carbon nanotubes were between nickel and silver in their effectiveness. They were less effective than nickel nanoparticles in spite of their high aspect ratio. Even the combined use of nanotubes and silver nanoparticles was less effective than nickel nanoparticles alone. The filler volume fractions are much lower than those in prior related work, and are therefore attractive for good bonding to the substrate, high processability and low cost.
In this work we investigated the correlation between the emission properties of Scandia doped dispenser cathodes and their surface features. A proposal for explanation of the observed phenomena has been suggested.
ISBN:
(纸本)9781424417155
In this work we investigated the correlation between the emission properties of Scandia doped dispenser cathodes and their surface features. A proposal for explanation of the observed phenomena has been suggested.
Nanoröhren vom Fließband : Hexabenzocoronen(HBC)‐Amphiphile mit pyridylterminierten Triethylenglycol‐Seitenketten bilden in Kombination mit trans ‐[Pt(PhCN) 2 Cl 2 ] graphitische Nanoröhren. Die Stru...
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Nanoröhren vom Fließband : Hexabenzocoronen(HBC)‐Amphiphile mit pyridylterminierten Triethylenglycol‐Seitenketten bilden in Kombination mit trans ‐[Pt(PhCN) 2 Cl 2 ] graphitische Nanoröhren. Die Strukturen und Abmessungen der Nanoröhren hängen dabei von den Synthesebedingungen ab. Auch Platin(II)‐verbrückte cyclische Dimere mit zwei HBC‐Einheiten bauen Nanoröhren auf.
SnO2 nanowires with a diameter of 25 nm are synthesized at 550C by Au-Ag catalyst assisted thermal evaporation of SnO powders. The room-temperature photoluminescence spectra (PL) of the prepared nanowires are measured...
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SnO2 nanowires with a diameter of 25 nm are synthesized at 550C by Au-Ag catalyst assisted thermal evaporation of SnO powders. The room-temperature photoluminescence spectra (PL) of the prepared nanowires are measured. Among the four PL peaks, the peak of 418 nm is newly observed. This peak is caused by the plane defects of the twinned crystal nanowires. The formation of SnO2 nanowires at low temperature is pursued on the basis of the VLS mechanism and application of the reaction source of SnO. We suggest that the chemical reactions of the low temperature and low concentration of the vaporized species are responsible for the thinner size of the SnO2 nanowires.
Modern levitation furnaces are enabling melting and freezing of refractory materials like Al 2 O 3 to be studied in depth with synchrotron radiation techniques. Whilst α-Al 2 O 3 is a close packed Debye-like solid, l...
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Modern levitation furnaces are enabling melting and freezing of refractory materials like Al 2 O 3 to be studied in depth with synchrotron radiation techniques. Whilst α-Al 2 O 3 is a close packed Debye-like solid, liquid Al 2 O 3 has smaller coordination numbers and the structure has network-like characteristics. Under contactless conditions, substantial under cooling can be achieved. Melting involves a significant decrease in density which is approximately recovered on recrystallization, both of which can be followed with high speed video imaging. Freezing occurs with a burst of energy — recalescence — which substantially raises the temperature momentarily. Using Rietveld refinement the density of α-Al 2 O 3 and the mean square displacement of the average atom 〈μ 2 〉 can be followed up to the melting point and upon freezing using in situ X-ray diffraction. As melting is approached 〈μ 2 〉 for α-Al 2 O 3 exceeds the harmonic approximation of the Lindemann–Galvarry law and for liquid Al 2 O 3 above the melting point 〈μ 2 〉 appears to be greater still. On freezing from the undercooled state α-Al 2 O 3 is initially decompressed with the T - P point falling on the melting curve extrapolated to negative pressures.
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