Narrow Results

We have applied density-functional theory (DFT) based calculations to investigate the size and strain effects on the electronic properties, such as band structures, energy gaps and effective masses of the electron and the hole, in Si nanowires along the 〈110〉 direction with diameters up to 5 nm. Under uniaxial strain, we find that the band gap varies with strain and this variation is size dependent. For the 1–2 nm wire, the band gap is a linear function of strain, while for the 2–4 nm wire the gap variation with strain shows nearly parabolic behaviour. This size dependence of the gap variation with strain is explained on the basis of orbital characters of the band edges. In addition we find that the expansive strain increases the effective mass of the hole, while compressive strain increases the effective mass of the electron. The study of size and strain effects on effective masses shows that effective masses of the electron and the hole can be reduced by tuning the diameter of the wire and applying appropriate strain.

The total hip replacement is the only approved procedure for restoring a degenerated hip joint through operation. The life span of a prosthesis could depend on the geometry and material properties of the implant. This study aims to analyze the biomechanics of the carbon/polyetheretherketone (PEEK) composite prosthesis having three different fiber ply configurations compared to traditional stainless steel (SS) ones. The implant-bone system was established and subjected to a load from the head of the femur and abductor muscle sides. The stresses and strains in the implant-bone systems were calculated and compared. The results revealed lower stresses and strains in composite prostheses compared to SS ones. The fiber ply orientation of the carbon/PEEK composite prosthesis is shown to be a key asset in stress and strain distribution of the 13 implant-bone systems. The fiber plies which orientated multidirectionally with −45 and +45 degrees exhibited uniform stress and strain distributions. The results suggested the advantage of using composite prostheses in implant designs as they not only invoke lower stresses and strains in the implant-bone system but also amplify the life span of implants in the body.

This paper aims to relate some properties of photon-like objects, considered as spatially finite time-stable physical entities with dynamical structure, to well defined properties of the corresponding electromagnetic strains defined as Lie derivatives of the Minkowski (pseudo) metric with respect to the eigen vector fields of the Maxwell-Minkowski stress-energy-momentum tensor. First we recall the geometric sense of the concept of strain, then we introduce and discuss the notion for PhLO. We compute then the strains and establish important correspondences with the divergence terms of the energy tensor and the terms determining some internal energy-momentum exchange between the two components F and _*F of a vacuum electromagnetic field. The role of appropriately defined Frobenius curvature is also discussed and emphasized. Finally, equations of motion and interesting PhLO-solutions are given.