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排序方式: 共有87条查询结果,搜索用时 15 毫秒
21.
提出一种激光诱导等离子体的主动抑制方法,以优化Ni30Cr25Al15Co15Mo5Ti5Y5高熵合金(HEA)涂层表面激光烧结(SLS)的晶体结构和摩擦学性能,该过程采用脉冲激光和不同保护气体。结果表明,无保护气体或He气氛下的电子温度(Te)和等离子体射流体积均高于Ar-He气氛下的。SLS过程中发生明显的相变和金属原子扩散,α-AlFe3、α-AlNi和γ-AlFe2Ni化合物沉淀形成冶金结合。等离子体通过逆韧致辐射(IB)吸收较低能量加强激光与HEA之间的相互作用,使涂层显微硬度增加,动态摩擦因数降低,这说明等离子体控制对激光增材制造存在重要影响。 相似文献
22.
Zhao Liu Huidan Zeng Xiaoming Ji Jing Ren Guorong Chen Junyi Ye Ye Dai Ya Cheng 《Journal of the American Ceramic Society》2015,98(2):408-412
We report on the formation of Bi2ZnB2O7 crystal structures with designated patterns in ZnO–Bi2O3–B2O3 glass by femtosecond laser direct writing. The crystallization mechanism in glass is investigated by crystallization kinetics analysis and simulation of the three‐dimensional temperature field distribution. The crystallized regions show larger third‐order optical nonlinearity than the unirradiated region in glass by Z‐scan technique. This finding is of great potential in application of nonlinear optical integrated devices and development of new nonlinear materials. 相似文献
23.
Daisuke Totsuka Takayuki Yanagida Makoto Sugiyama Yutaka Fujimoto Yuui Yokota Akira Yoshikawa 《Materials Research Bulletin》2012,47(4):993-997
In this work, we present results of structural characterization and optical properties including radio luminescence of (LuxGdyY0.99?x?yTm0.01)AP single crystal scintillators for (x, y) = (0.30, 0.19), (0, 0.19) and (0, 0) grown by the micro-pulling-down (μ-PD) method. The grown crystals were single phase materials with perovskite structure (Pbnm) as confirmed by XRD and had a good crystallinity. The distribution of the crystal constituents in growth direction was evaluated, and significant segregation of Lu and Gd was detected in (Lu0.30Gd0.19Y0.50Tm0.01)AP sample. The crystals demonstrated 70% transmittance in visible wavelength range and some absorption bands due to Tm3+, Gd3+ and color centers were exhibited in 190–900 nm. The radioluminescence measurement under X-ray irradiation demonstrated several emission peaks ascribed to 4f–4f transitions of Tm3+ and Gd3+. The ratio of emission intensity in longer wavelength range was increased when Y was replaced by Lu or Gd. 相似文献
24.
Wenwu Zhao Shilie Pan Xiaoyu Dong Junjie Li Xuelin Tian Xiaoyun Fan Zhaohui Chen Fangfang Zhang 《Materials Research Bulletin》2012,47(4):947-951
A new compound, Pb3OBO3F, has been grown by the high temperature solution method from the PbO–PbF2–B2O3 system. It crystallizes in the orthorhombic system, space group Pbcm with unit-cell parameters a = 7.6313(14) Å, b = 6.5229(12) Å, c = 11.906(2) Å, Z = 4, volume = 592.66(19) Å3. The structure of the compound is solved by the direct methods and refined to R1 = 0.0528 and wR2 = 0.1400. Pb3OBO3F consists of Pb(1)O3F tetrahedra, Pb(2)O4 tetrahedra and BO3 triangles which build up the symmetrical chains extended along the c-axis. The powder X-ray diffraction pattern of the Pb3OBO3F has been measured. Functional groups presented in the sample were identified by Fourier transform infrared spectrum. 相似文献
25.
26.
《Control Engineering Practice》2001,9(6):647-657
This paper deals with off-line parameter identification of induction motors by means of least square (LS) techniques and genetic algorithms (GA), using stator voltages, stator currents and velocity as input–output data. For analytical identification by LS algorithms, filtering of experimental data is performed by means of anticausal filters. Two models useful for identification are derived in which the products of acceleration and rotor fluxes, usually neglected, are taken into account. The GA-based identification method consists of the determination of the best parameters which match input–output behaviour of the motor. Both methods are investigated and compared by means of experiments carried out on a 1-kW induction motor. 相似文献
27.
太赫兹辐射极性和幅度依赖于双色场相位。由于等离子体光丝中色散和Gouy相移,导致双色场的相对相位随着激光的传播发生改变。当相位的改变量大于时,丝中的太赫兹电场极性发生反转,使得远场太赫兹辐射在离轴相位匹配角方向相干增强,而光轴前向相消减弱。通过对基频和倍频聚焦条件的调整和传输非线性色散的作用对双色场相对相位进行了调制,提出了可以使相对相位平缓的方法。模型计算证明了等离子体形成和Gouy相移调制是使双色场相移变平缓的原因。随后利用相位变平缓的条件得到了太赫兹发生极性反转的失相长度延长,最大长度近三倍于空气介质中的失相长度。在满足相位变平的条件下,远场太赫兹辐射在光轴前向的分布得到增强。 相似文献
28.
29.
A.?N.?ChumakovEmail author N.?A.?Bereza J.?D.?Hu N.?A.?Bosak Z.?X.?Guo Q.?Q.?Xie 《Journal of Engineering Physics and Thermophysics》2011,84(3):567-573
Experimental results on the nanostructural modification of an Al–C–Ti coating on magnesium alloy AZ91D under the multipulse
action of Nd:YAG lasers (λ = 1064 nm, τ = 20 ns, and E = 200 mJ) and Nd-glass lasers (λ = 1060 nm, τ = 85 ns, and E = 2 J)
are given. It is shown that the formation of the found nanocrystalline coating structure with a grain size of 35 to 400 nm
involves the process of background deposition of ablated particles and condensed clusters formed in the plasma plume. 相似文献
30.