Misfit dislocation dipoles in wire composite solids

Developed in this note is a theoretical model describing the mobility of a misfit screw dislocation dipole in a wire composite consisting of a stiff cylindrical substrate covered by a soft co-axial cylindrical film. A critical value of the film thickness, which is a function of the parameter measuring the stiffness of the film with respect to the substrate, is identified. It is observed that: (i) there exist two equilibrium positions of the misfit dislocation dipole (one stable and the other one unstable) when the film is thicker than the critical value; (ii) the two equilibrium positions of the misfit dislocation dipole converge to a single saddle point equilibrium position which is neither stable nor unstable when the thickness of the film is at the critical value; (iii) there exists no equilibrium position of the misfit dislocation dipole when the thickness of the film is below the critical value. These features could be useful to the design of wire composites and to the dislocation-related plasticity analysis.     

Influence of un-cured PDMS chains in stamp using PDMS-based lithography

We present the compatibility of elastomeric stamp, poly(dimethylsiloxane) (PDMS), with inks for non-photolithography. This ink limitation is important in considering the lamination of hydrophilic solution on the patterned ink surface using an elastomeric stamp. We focus on an increase of the hydrophobicity of the patterned surface due to diffusion of low molecular weight (LMW) silicone polymer chains. This hydrophobicity increases inversely with the PDMS–ink interaction parameter (χ), which is correlated with the solubility parameter (δ). This study's results translate into proposed design factors for ink used in the patterned functional layer for PDMS-based lithography. Both the XPS and the contact angle measurement show that the hydrophobicity can be increased by LMW PDMS chains transfer from stamps, and this increase can cause the expansion of the free volume in PDMS pores through a swelling effect.     

Area-selectively sputtering the RuO2 nanorods array

The RuO₂ nanorods array is grown selectively on the SiO₂-patterned sapphire (SA) wafers using reactive sputtering. The area-selectivity is attributed to an early nucleation of RuO₂ and its fast surface coverage on SA (1 0 0) and (0 1 2), in contrast to the sluggish nucleation on glassy SiO₂ in the initial sputtering period. The growth domain is explored by investigating the temperature windows at sputtering power 40, 50, and 60 W. The low-temperature bound is limited by the mobility of precursors on SiO₂ surface, which enables the precursors to depart before aggregating into a large size to smear the non-growth region. The high-temperature bound is set by the horizontal growth which enlarges the rod width and deteriorates its one-dimensional feature. The temperature window shrinks with increasing sputtering power. The X-ray photoelectron spectra indicate the as-sputtered rod surface is ruthenium rich. The X-ray diffraction analysis shows that RuO₂ growth on SA (1 0 0) and (0 1 2) follows the epitaxial relations between RuO₂ and SA crystals.     

Investigation of DKP equation for spin-zero system in the presence of Gödel-type background space-time

This paper contains a discussion of a relativistic spin-0 system in the presence of a Gödel-type background space-time. The Duffin–Kemmer–Petiau (DKP) equation in the presence of a Gödel-type background space-time is studied in detail. After a derivation of the final form of this equation in the considered framework, free spin-0 particles have been studied.     

Effect of post treatment on the photorefractive properties of Ru‐doped lithium niobate

The effect of post treatment on the photorefractive properties of Ru‐doped lithium niobate was studied. The absorption spectra examination of Ru‐doped LiNbO₃ crystals with different post treatments showed that the absorption coefficient at 530 nm increased after the reduced treatment was employed and the absorption edge of the reduced crystal shifted towards the infrared band. On the contrary, the trend reversed after the oxidized treatment was employed. In addition, the photorefractive properties were investigated with the two‐beam coupling method conducted via a 532 nm solid state laser. It was found that the oxidized Ru:LiNbO₃ had smaller exponential gain coefficient and diffraction efficiency because the charges in the shallow level were exchanged to the deep level. On the other hand, the reduced Ru:LiNbO₃ crystals had larger exponential gain coefficient and diffraction efficiency due to the increase of the Ru³⁺ which existed in the shallow level. The response times of both oxidized and reduced Ru:LiNbO₃ were longer than those of the as‐grown ones. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Cyclic Representation of the gl√q (n)-Covariant Oscillator Algebra

The cyclic representation ofgl_q (n)-covariant oscillator algebrais discussed by use of some noncommutating cyclicvariables.     

Experimental and numerical investigation of combined isotropic-kinematic hardening behavior of sheet metals

To prevent a sheet specimen from buckling subjected to a tension-compression cyclic loading, a new fixture has been developed to use with a regular tensile-compression machine. The novelty of this device lies in 4-block wedge design with pre-loaded springs. This design allows blocks to freely move in the vertical direction while providing the normal support to the entire length of the specimen during the tension-compression cycle. The entire test is easy to setup, which is another advantage of this design. In order to measure the strain accurately, the transmission type laser extensometer was utilized together with the implementation of double-side fins in the specimen. Experimental results of tension-compression tests are presented followed by a review of existing testing methods. In order to describe the accurate cyclic tension-compression behavior, the combined isotropic-kinematic hardening law based on the modified Chaboche model and the practical two-surface model based on Dafalias-Popov and Krieg models have been modified in this work, considering the permanent softening behavior during reverse loading and the non-symmetric behavior during reloading. Through tension-compression tests, the material characterization has been performed for three base materials, BH180, DP600 steels and AA6111-T4 sheets.     

Ultra-short distributed feedback fiber laser with sub-kilohertz linewidth for sensing applications

A low-noise, ultra-short linear-cavity distributed feedback fiber laser (DFB-FL) with extremely narrow linewidth is presented. The FL has a total length of 17 mm, which is, to our knowledge, the shortest DFB-FL being reported. It has a measured linewidth of merely 250 Hz without active stabilization. It has a polarization beat frequency of 101 MHz, which is several times lower than that of most FLs. The relaxation oscillation frequency and relative peak are 110 kHz and −76.5 dB/Hz, respectively. The FL exhibited low-noise characteristics, with an intensity noise of −107 dB/Hz at 1 MHz. Due to low dopant concentration of the EDF and low splice loss with ordinary single-mode fibers, the net insertion loss amounts to only 0.45 dB. Such low pump power loss greatly enhances the capability of multiplexing a large number of FL sensors. Thus, these ultra-short DFB-FLs open up new opportunities for the development of compact-sized point sensor array systems for large-scale high sensitivity sensing applications.