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A simple least-squares fitting-based method is described for the determination of strain profiles in epitaxial films using high-resolution X-ray diffraction. The method is model-independent,i.e.it does not require any `guess' model for the shape of the strain profile. The shape of the vertical displacement profile is modelled using the versatile cubicB-spline functions, which puts smoothness and curvature constraints on the fitting procedure. The effect of a coherently diffracting substrate is taken into account as well as the effects of film thickness fluctuations. The model is applied to the determination of strain profiles in SmNiO3films epitaxically grown on SrTiO3(001) substrates. The shape of the retrieved strain profile is discussed in terms of oxygen vacancies.

A continuum model that incorporates a dependence upon the Laplacian of the inelastic strain is used to regularize the initial value problem that results from the introduction of strain softening or non-associated flow. It is shown that the introduction of this gradient dependence preserves well-posedness of the initial value problem and that wave propagation in the enhanced continuum is dispersive. An analysis of the dispersive wave propagation reveals the existence of an internal length scale. Numerical analyses of one-dimensional and two-dimensional problems confirm that this internal length scale sets the localization zone and show that the results are insensitive to the fineness of the discretization and to the direction of the grid lines. This holds true with respect to the strain profiles, the energy dissipation and the extent of wave reflection.

Performance-based design approach of special moment-resistant reinforced concrete (RC) framed structures demands a thorough understanding of axial force-bending moment (P-M) yield interaction of RC elements, particularly when the structure is subjected to seismic loads. Latest design approach includes desirable features of both ultimate strength and working stress to ensure a suitable ductile deformation response. This demands a detailed understanding of nonlinear response of P-M interaction. A complete set of analytical expressions for P-M yield interaction are proposed in a closed form by defining the limit boundary with ten sub-domains based on Euro Code currently in prevalence. P-M interaction relationships are also verified for plastic flow-rule in two main sections namely: (i) tension failure resulting in yielding of steel; and (ii) compression failure resulting in crushing of concrete. The conventional limit P-M domain is described based on Euro Code as long as the plastic strain increment becomes nearly normal to the yield domain over the part of bending response in the presence of axial force. The verified flow rule shows a close agreement in all sub-domains of tension failure, while does not qualify in few of the sub-domains of crushing failure. Practical examples of RC sections are chosen to illustrate the influence of different parameters namely: (i) cross-section dimension; (ii) percentage of tension and compression reinforcements; and (iii) properties of constitutive materials on the P-M boundary. Mathematically developed P-M interaction model is capable of identifying the damage mechanism of different sub-domains in RC sections; damage identification is made on the basis of strain profile of concrete and reinforcing steel. � 2010 The Author(s).

Strain has a crucial effect on the optical and electronic properties of nanostructures. We calculate the atomistic strain distribution in silicon nanocrystals up to a diameter of 3.2 nm embedded in an amorphous silicon dioxide matrix. A seemingly conflicting picture arises when the strain field is expressed in terms of bond lengths versus volumetric strain. The strain profile in either case shows uniform behavior in the core, however it becomes nonuniform within 2-3 \AA distance to the nanocrystal surface: tensile for bond lengths whereas compressive for volumetric strain. We reconsile their coexistence by an atomistic strain analysis., Comment: Published in Applied Physics Letters Vol. 94, 191914 (2009)