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901.
X.-F. Li 《Philosophical Magazine Letters》2013,93(4):313-320
Dynamic problems of quasicrystals are analysed within the framework of continuum mechanics. Phonon excitations yield wave propagation while phason excitations yield atomic diffusion. Phonon fields obey the equations of motion and phason fields obey the diffusion equations. Governing equations of elasto-hydrodynamics of decagonal quasicrystals combine characteristics of the equations of motion and diffusion. A general solution is derived in terms of two introduced auxiliary functions. It provides an easy-to-use approach to solve initial-boundary value problems encountered in elasticity problems for quasicrystals. Explicit expressions for displacements and stresses in the phonon and phason fields can be directly obtained. A derived general solution is also applicable to some planar quasicrystals such as pentagonal quasicrystals with fivefold symmetry. 相似文献
902.
Y. Z. Liu H. T. Yuan Z. Q. Zeng X. L. Du X. D. Han Q. K. Xue 《Philosophical Magazine Letters》2013,93(9):687-693
Transmission electron microscopy has been used to investigate the (1100) and (1103) inversion domain boundaries in a ZnO film prepared by molecular beam epitaxy. The inversion domain was revealed by dark-field images and confirmed by convergent-beam electron diffraction. Interacting with a (0002) stacking fault, the inversion domain boundary in the (1100) plane alters its orientation from the [0001] direction and climbs on the (1103) plane to release the strain energy. These features are characterized and analysed by high-resolution electron microscopy and the geometric phase method. The findings are significant for understanding the formation and propagation of inverse domain boundaries in epitaxial ZnO films. 相似文献
903.
ABSTRACTThe propagation of shear horizontal (SH) surface waves in piezoelectric semi-infinite bodies is investigated theoretically. The surface stress exerting on the boundary is taken into account through surface piezoelectricity theory, and the velocity ranges and existence conditions of such surface waves for both electrically open and shorted cases are derived in detail. Analysis results show that the SH surface waves occurring with surface stress are dispersive in contrast to the classical situation, and the propagation characteristics strongly depend on the relative value of surface elasticity, surface piezoelectricity and surface density. 相似文献
904.
X. Y. Zhang Z. L. Hu S. J. Zhou C. Jia M. Z. Zhou B. Y. Xia 《Philosophical Magazine Letters》2013,93(11):595-601
A study was carried out on the deformation of nanocrystalline cobalt. For cold-rolled nanocrystalline cobalt, the X-ray diffraction peaks narrowed instead of broadened on deformation. The results of transmission electron microscopy showed that grain size (17.8?nm on average) was not increased. The results can be explained in terms of the production and activity of vacancies and vacancy clusters. 相似文献
905.
The Ti36Ni41Hf15Cu8 melt-spun ribbon undergoes a B2 ? B19′ transformation upon cooling and heating. When the Ti36Ni41Hf15Cu8 melt-spun ribbon is annealed at 873 K for 1 h, the spherical (Ti, Hf)2Ni particles with a diameter of 20–40 nm precipitate in the grain interior. The fine (Ti, Hf)2Ni precipitates improve the stability of phase transformation temperatures and cause martensite domains, with (001) compound twins in three orientations dominant instead of (011) type I twins. {111}-, {113}- and (001)//{111}-type boundaries are observed among these martensite domains. When the (Ti,Hf)2Ni precipitates coarsen, (011) type I twins become main martensite structures in the ribbon annealed at 973 K for 1 h. 相似文献
906.
A complete diagonalization energy matrix method (CDM) is proposed for 3d 8 ions in orthorhombic site (D 2 h ) symmetry. As an application, the optical spectra of XF2 : Ni2+ (X = Mg, Zn) is well explained on the basis of both the CDM and the semi-self-consistent field d-orbital (semi-SCF d-orbital) theory. In addition, by establishing the relationship between the optical spectra and local structure, it has been possible to calculate the crystal structure parameters for XF2:Ni2+ from optical measurements on Ni2+ ions. The theoretical results are in good agreement with experimental findings. 相似文献
907.
Off-axis electron holography has been used to map the electric potential derived from the spontaneous polarity in a ZnO film. A wedge-shaped ZnO film, in which the holograms and the object wave were reconstructed, was used. To interpret the phase image correctly, the reconstructed amplitude image was used to obtain information on the thickness, which was then applied to eliminate the thickness effect on the phase shift. The electric potential distribution was characterized and the polarity of the ZnO film determined. 相似文献
908.
A. Shamimi Nouri X.J. Gu S.J. Poon G.J. Shiflet J.J. Lewandowski 《Philosophical Magazine Letters》2013,93(11):853-861
Systematic changes in composition were employed to increase the notch toughness of a variety of Fe-based Bulk Metallic Glasses (BMGs). The Fe50Mn10Mo14Cr4C16B6 BMG possessed very high hardness (e.g. 12 GPa) but very low notch toughness (e.g. 5.7 MPa m1/2) at room temperature, consistent with fracture surface observations of brittle features. Many of the other Fe-BMG variants, created to change the Poisson's ratio via systematic changes in alloy chemistry, exhibited higher toughness but more scatter in the data, reflected in a lower Weibull modulus. SEM examination revealed fracture initiation always occurred at inclusions in samples exhibiting lower toughness and/or Weibull modulus for a given chemistry. Implications of these observations on reliability of BMGs are discussed. 相似文献
909.
Nanoparticles on the fracture surfaces of Co- and Fe-based metallic glasses during quasi-static compression at room temperature have been observed using a high-resolution scanning electron microscope. In terms of the differential scanning calorimeter, those nanoparticles were identified to be a result of nanocrystallization induced by the rapid fracture. Finally, the nanocrystallization behavior was evaluated by taking into account the super-high crack propagation rate and high elastic energy, which contributed to the local temperature rise up to the onset of crystallization, T x. 相似文献
910.
George V. Gushue Brenda X. Mejia-Smith Lauren D. Fisher Alise Cogger Melissa Gonzalez-Matthews Yi-Jung Lee 《Counselling psychology quarterly》2013,26(3-4):343-361
This study explored the relationship between personal identity development and in-group/out-group identities within the sociopsychological context of the USA. Specifically, the study examined the relationship between Bowen’s construct of differentiation of self and Helms’ construct of racial identity for an American sample of 309 undergraduate and graduate students. Insofar as both models refer to a progression from an externally defined sense of self to an internally defined sense of self, it was hypothesized that higher levels of more sophisticated racial identity statuses would be positively associated with higher levels of self-differentiation for both white participants and participants of color. Overall, the findings suggest that for white students, attitudes associated with a more differentiated sense of self are also associated with a more sophisticated racial identity statuses, increased awareness of how white privilege and racism operate, and less internal conflict about one’s own racial identity. The results of this study also indicated that, in general, participants of color who have a more differentiated sense of self endorse attitudes associated with higher statuses of racial identity development, more awareness of societal racism, and less ambivalence about their racial identity. Implications of the findings for the practice of counseling and the training of counseling psychologists are considered. 相似文献