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791.
792.
793.
Structural characteristics of 2024 aluminum alloy plasma-based ion implanted with nitrogen then titanium 总被引:1,自引:0,他引:1
J.X. Liao L.F. Xia M.R. Sun W.M. Liu T. Xu C.R. Yang H.W. Chen C.L. Fu W.J. Leng 《Applied Surface Science》2005,240(1-4):71-76
As an interlayer in the gradient layers such as AlN/Ti/TiN/DLC prepared by plasma-based ion implantation (PBII) on 2024 aluminum alloy, titanium layer plays an important role in enhancing adhesion, reducing thermal stress, limiting the crack propagation, etc. A series of dual-layers prepared by PBII with nitrogen then titanium at various sputtering currents of titanium target on 2024 aluminum alloy have been reported in this paper. The composition distributions and the chemical states are analyzed using X-ray photoelectron spectroscopy (XPS). The structures are studied with grazing X-ray diffraction (GXRD). The results show that PBII with titanium strongly depends on the sputtering current. It is found that there exists a critical sputtering current corresponding only to a titanium-implanted layer containing TiAl3. When the sputtering current exceeds the critical value, a titanium-deposited layer rich in -Ti is formed on a titanium-implanted layer. By controlling the sputtering current an appropriate titanium interlayer can be prepared to meet the requirement of forming a proper gradient layer. 相似文献
794.
Chunmei Zhang Jianliang Wang Xiaowei Chen Yuxin Leng Ruxin Li Zhizhan Xu 《Laser Physics》2009,19(8):1793-1795
The seventh harmonic generation by tunable mid-infrared femtosecond pulses filamentation in air is observed first time. Pumped by a focused mid-infrared pulses, which pulse duration is ~50 fs and wavelength is tunable from 1300 to 2000 nm, the tunable region of the fifth and seventh harmonic generation can cover the near ultraviolet region from 180 to 400 nm. 相似文献
795.
Yong-Chang Huang Leng Liao Xie-Guo Lee 《The European Physical Journal C - Particles and Fields》2009,60(3):481-487
We generalize the Faddeev–Jackiw canonical path integral quantization for the scenario of a Jacobian with J=1 to that for the general scenario of non-unit Jacobian, give the representation of the quantum transition amplitude with
symplectic variables and obtain the generating functionals of the Green function and connected Green function. We deduce the
unified expression of the symplectic field variable functions in terms of the Green function or the connected Green function
with external sources. Furthermore, we generally get generating functionals of the general proper vertices of any n-points
cases under the conditions of considering and not considering Grassmann variables, respectively; they are regular and are
the simplest forms relative to the usual field theory. 相似文献
796.
We investigate experimentally the linear viscoelastic properties of a lamellar liquid foam as a function of the cell size
and spatial organisation. The system consists of multilamellar vesicles generated by a simple shear flow on a lyotropic lamellar
phase. The vesicles can be prepared either in an amorphous or a spatially ordered state. Their size is easily tunable in the
range R = 0.5-15 μm. Whereas the shear modulus of the amorphous lamellar foam is alike that of usual liquid foams or concentrated
emulsions and scales linearly with 1/R, the elastic modulus of the ordered foam is almost independent of the cell size. This result --probably the first describing
the elasticity of an ordered foam-like system-- remains unexplained.
Received 7 August 2000 相似文献
797.
Pin Wai Koh Tiem Leong Yoon Thong Leng Lim Yee Hui Robin Chang 《International journal of quantum chemistry》2019,119(10):e25884
Structural and electronic properties of ternary clusters AlkTilNim, where k, l, and m are integers and k + l + m = 4 , are investigated. These clusters are generated and studied by performing a two-stage density functional theory (DFT) calculations using the Slater, Vosko, Wilks, and Nusair (SVWN) and Becke three-parameter, Lee-Yang-Parr (B3LYP) functional exchange correlations. In the first stage, an unbiased global search algorithm coupled with a DFT code with a light exchange-correlation and smaller basis sets are used to generate the lowest energy cluster structures. It is then followed by further optimization using another round of DFT calculation with heavy exchanged correlations and large basis set. Electronic properties of the structures obtained via the two-stage procedure are then studied via DFT calculations. The results are illustrated in the form of ternary diagram. Our DFT calculations find that the stability of the cluster increases with the increase in the number of nickel atoms inside the clusters. Our findings provide new insight into the ternary metallic cluster through the structure, stability, chemical order, and electronic properties studies. 相似文献
798.
Zehai Lu He Liu Shihan Liu Xuebing Leng Yu Lan Qilong Shen 《Angewandte Chemie (International ed. in English)》2019,58(25):8510-8514
The synthesis, characterization, and C(sp2)?CF3 reductive elimination of stable aryl[tris(trifluoromethyl)]cuprate(III) complexes [nBu4N][Cu(Ar)(CF3)3] are described. Mechanistic investigations, including kinetic studies, studies of the effect of temperature, solvent, and the para substituent of the aryl group, as well as DFT calculations, suggest that the C(sp2)?CF3 reductive elimination proceeds through a concerted carbon–carbon bond‐forming pathway. 相似文献
799.
Optimization control of modulation-instability gain in photonic crystal fibres with two-zero dispersion wavelengths 下载免费PDF全文
We design three kinds of photonic crystal fibres (PCF)
with two zero-dispersion wavelengths (ZDWs) using the improved full
vector index method (FVIM) and finite-difference frequency domain
(FDFD) techniques. Based on these designed fibres, the effect of
fibre structure, pump power and wavelength on the modulation
instability (MI) gain in the anomalous dispersion region close to
the second ZDW of the PCFs is comprehensively analysed in this paper.
The analytical results show that an optimal MI gain can be obtained
when the optimal pump wavelength (1530~nm) is slightly shorter than
the second ZDW (1538~nm) and the optimal pump power is 250~W.
Importantly, the total MI gain bandwidth has been increased to 260~nm
for the first time, so far as we know, for an optimally-designed fibre
with Λ = 1.4~nm and d/Λ = 0.676, and
the gain profile became much smoother. The optimal pump wavelength
relies on the second ZDW of the PCF whereas the optimal pump power
depends on the corporate operation of the optimal fibre structure and
optimal pump wavelength, which is important in designing the most
appropriate PCF to attain higher broadband and gain
amplification. 相似文献
800.
Fei Leng Gao Lin 《Acta Mechanica Solida Sinica》2010,23(2):147-155
An energy-dissipation based viscoplastic consistency model is presented to describe the performance of concrete under dynamic loading. The development of plasticity is started with the thermodynamic hypotheses in order that the model may have a sound theoretical background. Independent hardening and softening and the rate dependence of concrete are described separately for tension and compression. A modified implicit backward Euler integration scheme is adopted for the numerical computation. Static and dynamic behavior of the material is illustrated with certain numerical examples at material point level and structural level, and compared with existing experimental data. Results validate the effectiveness of the model. 相似文献