New CPW-fed monopole antennas with both linear and circular polarisations

A low-profile, planar, circularly polarised monopole antenna with a shorting sleeve strip fed using a coplanar-waveguide transmission line for wireless communication in the digital communication system and the global positioning system bands is studied. By utilising the coupling effect between the monopole antenna and sleeve, two excited resonant modes, including the monopole and travelling-wave modes, cover the 1.57- and 1.8-GHz bands. Through modification with antennas of various geometrical parameters, the proposed antenna exhibits the wide bandwidth in the desired frequency bands, which has a bandwidth of 45% at 1.6%GHz for an input reflection coefficient of less than %10%dB. Meanwhile, the antenna has a 3-dB axial ratio bandwidth of 5%. Details of the design considerations for the proposed antennas are described, and the results of the antenna performances obtained are presented and discussed.     

Spatial solitons in biased photorefractive materials with both the linear and quadratic electro-optic effects

Unlike previous cases discussed, non-linear changes of refractive index in the photorefractive (PR) materials are governed by both the linear and quadratic electro-optic (EO) effects simultaneously now. Here, the evolution equations of one-dimension spatial solitons resulting from both the linear and quadratic EO effect are presented firstly. Under appropriate conditions, our analysis indicates that bright, dark, and gray solitons can exist in the steady-state regime. Moreover, stabilities of bright and dark soliton propagation are analyzed by means of beam propagation methods. The analytical solutions in the low-amplitude regime are also obtained. The self-deflection of such bright spatial solitons arising from diffusion effect in biased PR crystals involving both the linear and quadratic EO effects has been investigated symmetrically by the use of numerical techniques and perturbation methods.     

Coating cracks in materials with general anisotropy

The problem of a straight crack lying in the coating of a semi-infinite substrate is considered. The most general case of anisotropy is assumed for both materials (coating and substrate). The solution of Atkinson and Eftaxiopoulos [2] for a dislocation in an anisotropic bimaterial is modified to solve the fundamental problem of a dislocation in the coating, by including a corrective solution that accounts for the additional boundary conditions at the free surface. The coating crack is modelled as a continuous distributions. The resulting system of singular integral equations is solved by applying an inversion theorem and then using numerical integration. The stress intensity factors for modes I, II and III can be directly obtained from the dislocation densities. Numerical results are presented to compare the present analysis with existing solutions for some particular geometries and material models. For the general anisotropic case, results are presented showing the influence of a number of geometric and material parameters.     

Nonuniform transformation field analysis of materials with morphological anisotropy

The effective properties of metal matrix composites with particulate reinforcement are investigated using the nonuniform transformation field analysis (NTFA) developed by Michel and Suquet [30]. In particular the effect of the particle morphology on the effective mechanical response is examined in detail. For that, an existing periodic three-dimensional mesh generation technique for particulate composites is extended to allow for anisotropic morphologies. It is shown that the effects induced by the anisotropic particles can be captured by the NTFA. Additionally, the load partitioning between reinforcement and matrix material is investigated and a good agreement to full-field computations is attained with the NTFA.     

Permanent magnets based on materials with high crystal anisotropy

The properties of Alnicos and elongated single-domain fine-particle materials, both interpreted as due to shape anisotropy of fine particles, are still far short of those predicted by simple theory. The hard ferrites, with properties due to magnetocrystalline anisotropy, come much closer, but are restricted by their low magnetization. The search for a combination of high magnetization and high magnetocrystalline anisotropy has led to the investigation of a variety of intermetallic compounds. Some of them, particularly the cobalt-rare earths, appear quite promising. Mechanical grinding often has an adverse effect on the magnetic properties of crystal anisotropy materials. Chemical stability is also often a problem. Crystal anisotropy materials in general have high values of intrinsic coercive force. This makes them especially suitable for applications involving widely varying dynamic conditions. Their proper evaluation may be best done using criteria other than the usual maximum energy product.     

Spiraling elliptic breathers in nonlocal nonlinear media with linear anisotropy

The dynamical properties of spiraling elliptic breathers in nonlocal nonlinear media with linear anisotropy are analytically discussed. Using a two-dimensional asynchronous fractional Fourier transform, the exact analytical solutions of spiraling elliptic breathers are obtained to the nonlocal nonlinear Schrödinger equation with unequal diffraction coefficients in the highly nonlocal limit. It is found that the spiraling elliptic breathers exhibit a kind of molecule-like libration due to the combined effects of the linear anisotropy and the orbital angular momentum. The angular velocity of the spiraling elliptic breathers is discussed, which can be controlled by the linear anisotropy parameter. In the media with linear anisotropy such as uniaxial crystals, the angular velocity of the spiraling elliptic breathers can be controlled by changing the propagation directions of optical beams. Furthermore, the nonlinearity of media is found to enhance the rotation effect of spiraling elliptic breathers.     

Laser linear encoder with both high fabrication and head-to-scale tolerances

We introduce a new configuration for the optical head of a newly developed diffractive laser encoder system. This configuration has a high manufacturing tolerance and a high head-to-scale alignment tolerance, both of which can enhance the wider potential applicability of this newly designed laser encoder. The measurement principles of the encoder are discussed and detailed. We optimized the grating shape and analyzed the impact of the optical components and their arrangement on the measurement error. The head-to-scale alignment tolerance and the arrangement of components in the encoder were also determined. Finally, the measurement performance was evaluated and analyzed. Under nonenvironmentally controlled conditions, the measurement accuracy was found to be 37.3 nm with a standard deviation of 25.4 nm.     

Elastic and thermal expansion anisotropy of oriented linear polyethylene

A two-phase composite laminate model is proposed for representing biaxially oriented sheets of linear polyethylene. Thermoelastic analysis of the model yields predictions of the complete elastic and thermal expansion anisotropy. These predictions are compared with experimental measurements of elastic compliance and thermal expansivity obtained with the same oriented sheets. Using only one adjustable parameter (Poisson's ratio of non-crystalline linear polyethylene), extensive qualitative agreement is obtained between model predictions and experimental results. Discrepancies which are observed are attributed to the influence of the interfacial regions which exist between adjacent stacks of lamellar crystals in the real oriented sheets.     

Crystallography-based prediction of plastic anisotropy of polycrystalline materials

The on-line prediction of metal sheet formability requires that both material characterization (texture identification) and yield loci predetermination be done in very shor time intervals. Of two applicable approaches, i.e., continuum mechanics and crystallography-based methods, only the latter are suitable for this purpose. Several models of plasticity of a polycrystalline material were reviewed, and their applicability to the prediction of plastic anisotropy of face-centered cubic (FCC) metals was evaluated. A tailored set of cold-rolled copper alloy samples was designed and manufactured, representing the wide spectrum of textures and cold work levels typical for the sheet metal industry. The texture was quantitatively described in the form of the orientation distribution functions derived by the inversion of four incomplete pole figures. The Taylor-Bishop-Hill model was applied in order to calculate the planar variation of the plastic strain ratio. The continuum mechanics of textured polycrystals approach was also used for the prediction of the plastic strain-rate ratio for the same set of deformed materials. The theoretical predictions were compared with the plastic strain ratios measured in tensile tests using strain gauges. The applicability of the models for prediction of the plastic anisotropy of FCC metals was discussed in view of the operating deformation mechanisms and other factors such as strain hardening sensitivity and grain size/shape effects.     

Polarization holographic gratings in side-chain azobenzene polyesters with linear and circular photoanisotropy

We investigate thin phase polarization holographic gratings recorded with two waves with orthogonal linear polarizations in materials in which illumination with linearly/circularly polarized light gives rise to linear/circular birefringence. The theoretical analysis shows that the presence of circular photoanisot-ropy changes significantly the diffraction characteristics of the gratings. The intensities of the waves diffracted in the +1 and -1 orders of diffraction and their ratio depend substantially on the reconstructing-wave polarization. Experiments with films of side-chain liquid-crystalline azobenzene polyester that is a photoanisotropic material of the considered type confirm the unusual polarization properties. It is shown that polarization holography may be used for real-time simultaneous measurement of photoinduced linear and circular birefringence.     

Damage of short-fibre reinforced materials with anisotropy induced by complex fibres orientations

In this paper, a behaviour model for damageable elastoplastic materials reinforced with short fibres that have complex orientations is proposed. The composite material is seen as the assembly of the matrix medium and several linear elastic fibre media. Its macroscopic behaviour is computed thanks to an additive decomposition of the state potential, with no need to implement complex methods of homogenisation. A 4th-order tensor that depends on the characteristics of each fibre medium is introduced to model the anisotropic damage of the matrix material induced by the reinforcement, as well as the progressive degradation of the fibre–matrix interface. The division of short fibres into several families means that complex distributions of orientation or random orientation can be easily modelled. The model is tested for the case of a polyamide reinforced with different contents of short-glass fibres with distributed orientations and subjected to uniaxial tensile tests in different loading directions. The comparison of the results with experimental data (extracted from the literature) demonstrates the efficiency of the model.     

Probing magnetic anisotropy and spin polarization in spintronic materials

Magnetic anisotropy and spin polarization are fundamental parameters in ferromagnetic materials that have use in spintronic device applications. As the need for screening properties of new magnetic materials rises, it is important to have measurement probes for quantities such as anisotropy and spin polarization. We have developed two unconventional yet powerful techniques to study these parameters. A resonant RF transverse susceptibility method is used to map the characteristic anisotropy and switching fields over a wide range in temperature and magnetic fields. For studies of spin polarization, the phenomenon of Andreev reflection across ferromagnet-superconductor junctions is used to extract values of the transport spin polarization. The effectiveness of these approaches is demonstrated in candidate spintronic materials such as half-metallic CrO/sub 2/ thin films and arrays of monodisperse, single-domain Fe nanoparticles.     

Failure criteria for linear elastic materials with U-notches

This paper provides a simple, albeit accurate, criterion for prediction of the rupture loads of brittle, or quasi-brittle, U-notched samples, where linear elastic fracture mechanics is not applicable because blunted notches do not exhibit stress singularities. Good agreement is found between numerical predictions and experimental results. The results of fracture tests from 18 different ceramic materials and a polymer (at − 60°C) are summarized and are used as a reference for checking the fracture criterion. Seven fracture criteria are reviewed and it is shown that all can be recast into the proposed criterion.     

Backscatter linear and circular polarization analysis of roughened aluminum

A study of cross-polarized and copolarized intensities backscattered from roughened aluminum surfaces is presented for both linear and circular incident polarization states. The angular variation of measured Mueller matrices is shown to contain only diagonal elements, as predicted by the reciprocity theorem. The ratio of cross-depolarized to copolarized scattered intensities is significantly larger for circular than for linear input polarization states. In the linear case the ratio saturates beyond 50 degrees , whereas in the circular case the ratio continues to increase monotonically with angle. A phenomenological model for copolarization and cross-polarization intensities is shown to predict the observed behavior of both linear and circular input polarization states up to incident angles of 70 degrees .     

Influence of anisotropy and lubrication on wrinkling of circular plates using bifurcation theory

In this research, wrinkling in cylindrical deep drawing of a circular plate in the flange area is studied and the critical blank holder force in the deep-drawing operations has been achieved. Analytical model based on the Hill’s bifurcation method is used with regard to the inner edge of an annular plate that is subjected to tensile stress. The analysis is formulated in the form of large deformation assumption. The friction between the plate and the die, and the strain-hardening parameters are also investigated. The result of this analysis is the critical blank holder force, which is related to the critical wrinkling condition in the flange area. The Abaqus/Explicit is also used for the finite element simulations. Experimental study in order to validate the results of the analytical and finite element simulations has been performed. Analytical method, experimental tests and finite element method have been investigated to obtain critical blank holder force for four materials: ST12, ST14, copper and brass. These results showed that ST12 and copper plates have the highest and lowest compressive instability, respectively. To study the effect of plastic anisotropy of sheet on the wrinkling, some cold work operations and then heat treatment operations was carried out on three different types of plate parts. The results show that by increasing the plastic anisotropy of plate, wrinkling is partially delayed. The effect of lubricant used in the experimental tests, has been also studied. The effect of three various yield functions on the critical blank holder force, has been studied.     

Piecewise linear interval maps both expanding and contracting

The dynamics of piecewise linear interval maps is studied with two branches, one expanding and one contracting. It is proved that such a map either has a periodic attractor or it is eventually expanding. In the latter case there exists an absolutely continuous invariant measure.