Sharif Digital Repository

Using the mathematical framework of surface elasticity theory, an analytical solution is presented for Love and Rayleigh surface wave propagations in a semi-infinite medium with face-centered cubic (fcc) single crystal structure. Previous formulations within surface elasticity have been based on the simplistic assumption of isotropy. Two different crystallographic orientations with respect to the incident wave vector are examined: (a) the free surface of the half-space is (010) plane and the surface waves propagate in [100] direction, (b) the free surface of the half-space is (110) plane and the surface waves propagate in [11¯0] direction. It is well-known that, contrary to the predictions... 

Propagation of the torsional surface waves in a medium consisting of a functionally graded (FG) substrate bonded to a thin piezoelectric over-layer has been analytically formulated in the mathematical framework of surface/interface elasticity theory. In the cases where the wavelength and/or the thickness of the over-layer are comparable to the surface/interface characteristic length, then the surface/interface effects are not negligible. It is assumed that the over-layer is made of hexagonal 622 crystals with a single axis of rotational symmetry coinciding with the axis of polarization. The half-space is made of an FG transversely isotropic material in which the elasticity tensor and the... 

Shear horizontal surface acoustic waves (SAW) propagation in an ultra-thin functionally graded piezoelectric (FGP) layer bonded to a homogeneous substrate is analytically formulated in the mathematical framework of surface/interface elasticity theory. It is assumed that the FGP over-layer is made of a hexagonal 6-mm crystal with a single axis of rotational symmetry coinciding with the axis of polarization. The mechanical and piezoelectric properties of the layer are assumed to vary linearly with thickness. The half-space is made of a transversely isotropic material. It should be mentioned that this model is of great interest in investigating SAW devices at high frequencies. Accounting for... 

Using the mathematical framework of surface/interface elasticity theory, an analytical solution is presented for the antiplane scattering of Love waves by a surface-breaking crack normal to the free surface of an ultra-thin layer bonded to a semi-infinite medium. Fourier transform technique is used to formulate the corresponding mixed-boundary value problem as a singular integral equation of Cauchy type. Within the context of the present theory, the scattered stress field, the Mode III dynamic stress intensity factor (DSIF) at the crack-tip, and the reflection coefficient at large distances from the crack face are computed and plotted for different wave numbers and surface/interface... 

The misfit strain within the core of a two-phase free-standing core-shell nanowire resulting in the generation of an edge misfit dislocation or an edge misfit dislocation dipole at the core-shell interface is considered theoretically within both the classical and surface/interface elasticity approaches. The critical conditions for the misfit dislocation generation are studied and discussed in detail with special attention to the non-classical surface/interface effect. It is shown that this effect is significant for fine cores of radius smaller than roughly 20 interatomic distances. The positive and negative surface/interface Lamé constants mostly make the generation of the misfit dislocation... 

A combination of measurements of the inclusive top-quark pair production cross-section performed by ATLAS and CMS in proton–proton collisions at centre-of-mass energies of 7 and 8 TeV at the LHC is presented. The cross-sections are obtained using top-quark pair decays with an opposite-charge electron–muon pair in the final state and with data corresponding to an integrated luminosity of about 5 fb−1 at s = 7 TeV and about 20 fb−1 at s = 8 TeV for each experiment. The combined cross-sections are determined to be 178.5 ± 4.7 pb at s = 7 TeV and 243.3−5.9+6.0 pb at s = 8 TeV with a correlation of 0.41, using a reference top-quark mass value of 172.5 GeV. The ratio of the combined cross-sections...