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排序方式: 共有775条查询结果,搜索用时 31 毫秒
711.
712.
Vittorio Vercillo Simone Tonnicchia Jean‐Michel Romano Antonio García‐Girn Alfredo I. Aguilar‐Morales Sabri Alamri Stefan S. Dimov Tim Kunze Andrs Fabin Lasagni Elmar Bonaccurso 《Advanced functional materials》2020,30(16)
Ice accretion on external aircraft surfaces due to the impact of supercooled water droplets can negatively affect the aerodynamic performance and reduce the operational capability and, therefore, must be prevented. Icephobic coatings capable of reducing the adhesion strength of ice to a surface represent a promising technology to support thermal or mechanical ice protection systems. Icephobicity is similar to hydrophobicity in several aspects and superhydrophobic surfaces embody a straightforward solution to the ice adhesion problem. Short/ultrashort pulsed laser surface treatments are proposed as a viable technology to generate superhydrophobic properties on metallic surfaces. However, it has not yet been verified whether such surfaces are generally icephobic under representative icing conditions. This study investigates the ice adhesion strength on Ti6Al4V, an alloy commonly used for aerospace components, textured by means of direct laser writing, direct laser interference patterning, and laser‐induced periodic surface structures laser sources with pulse durations ranging from nano‐ to femtosecond regimes. A clear relation between the spatial period, the surface microstructure depth, and the ice adhesion strength under different icing conditions is investigated. From these observations, a set of design rules can be defined for superhydrophobic surfaces that are icephobic, too. 相似文献
713.
In this paper, a comparison between two particle image velocimetry (PIV) systems, one based on a standard cross-correlation
charge coupled device (CCD) camera with pulsed laser and another using high-speed complementary metal oxide semiconductor
(CMOS) camera with continuous laser is performed. The objective of the paper is to point out advantages and disadvantages
of the two systems when computing large and small flow scale statistics. The comparison is performed on velocity measurements
in the near and far fields of a circular water jet: on this flow several experimental data and empirical self-similarity laws
are available for comparisons. The results show that both systems are suitable for measurements with a preference for the
standard one when investigating small-scale statistics. This result depends on the lower number of effectively independent
samples acquired by a high-speed system and on the higher noise levels of CMOS sensors in comparison to CCDs. 相似文献
714.
Bour D.P. Kneissl M. Van de Walle C.G. Evans G.A. Romano L.T. Northrup J. Teepe M. Wood R. Schmidt T. Schoffberger S. Johnson N.M. 《Quantum Electronics, IEEE Journal of》2000,36(2):184-191
We describe the design and performance characteristics of an asymmetric waveguide nitride laser diode structure, in which the p-cladding layer is placed immediately over the multiple-quantum-well (MQW) active region. Its close proximity to the active region enables it to serve not only as a cladding layer, but also as a potential barrier that confines injected electrons. This structure represents a departure from conventional nitride laser diode structures, where electron confinement is provided by a separate high-aluminum-content AlGaN tunnel barrier layer placed over the MQW active region. The optical confinement factor (Γ) remains: comparable to that of the conventional structure, in spite of the QW's displacement from the center of the waveguide. Room-temperature CW operation was achieved with this structure 相似文献
715.
716.
T.V. Kononenko S.V. Garnov S.M. Pimenov V.I. Konov V. Romano B. Borsos H.P. Weber 《Applied Physics A: Materials Science & Processing》2000,71(6):627-631
Laser ablation of thin TiN films deposited on steel substrates has been studied under wide-range variation of irradiation
conditions (pulsewidth, wavelength, energy density and spot size). It has been demonstrated that both picosecond (150–300 ps)
and nanosecond (5–9 ns) laser pulses were suitable for controllable ablation and microstructuring of a 1-μm-thick TiN film
unlike longer 150-ns pulses. The ablation rate was found to be practically independent of the wavelength (270–1078 nm) and
pulsewidth (150 ps–9 ns), but it increased substantially when the size of a laser spot was reduced from 15–60 μm to 3 μm.
The laser ablation technique was applied to produce microstructures in the thin TiN films consisting of microcraters with
a typical size of 3–5 μm in diameter and depth less than 1 μm. Tests of lubricated sliding of the laser-structured TiN films
against a steel ball showed that the durability of lubricated sliding increased by 25% as compared to that of the original
TiN film.
Received: 28 July 1999 / Accepted: 17 April 2000 / Published online: 20 September 2000 相似文献
717.
Giovanni Romano Raffaele Barretta Marina Diaco 《Continuum Mechanics and Thermodynamics》2016,28(6):1659-1670
The kinematics of generalized continua is investigated and key points concerning the definition of overall tangent strain measure are put into evidence. It is shown that classical measures adopted in the literature for micromorphic continua do not obey a constraint qualification requirement, to be fulfilled for well-posedness in optimization theory, and are therefore termed redundant. Redundancy of continua with latent microstructure and of constrained Cosserat continua is also assessed. A simplest, non-redundant, kinematic model of micromorphic continua, is proposed by dropping the microcurvature field. The equilibrium conditions and the related variational linear elastostatic problem are formulated and briefly discussed. The simplest model involves a reduced number of state variables and of elastic constitutive coefficients, when compared with other models of micromorphic continua, being still capable of enriching the Cauchy continuum model in a significant way. 相似文献
718.
Nonlinear asymptotic Lyapunov stability of the equilibrium state for the balance equations of charge transport in semiconductors based on the maximum entropy principle [A.M. Anile, V. Romano, Non parabolic band transport in semiconductors: closure of the moment equations, Contin. Mech. Thermodyn. 11 (1999) 307–325; V. Romano, Non parabolic band transport in semiconductors: closure of the production terms in the moment equations, Contin. Mech. Thermodyn. 12 (2000) 31–51] is proven for a typical 1-D problem. 相似文献
719.
720.
N. Soić D. Cali S. Cherubini E. Costanzo M. Lattuada M. Milin Đ. Miljanić S. Romano C. Spitaleri M. Zadro 《The European Physical Journal A - Hadrons and Nuclei》1998,3(4):303-305
Spectra of coincident charged particles from the reactions induced by a 52 MeV 7Li beam incident on a beryllium target were measured. Strong contributions of the 7Li quasi-free scattering off the α-cluster in 9Be nucleus were observed. This observation supports the conclusions from the study of complete fusion of weakly bound light
nuclei at low energies that the “fragility” of the nuclei makes their fusion less probable.
Received: 1 June 1998 相似文献