Reversible and irreversible switching processes in pure and lanthanum modified lead zirconate thin films

The mechanism of field induced phase switching in antiferroelectric lead zirconate and La-modified lead zirconate thin films has been analysed in terms of reversible and irreversible switching process under weak fields as a function of donor concentration. Extension of Rayleigh law of ferromagnetic materials to the present antiferroelectric and modified antiferroelectric compositions have clearly showed that origin of small signal dielectric permittivity is due to reversible domain wall motion. Rayleigh's constant, a measure of irreversible switching process, exhibited a slight increase with lower La3+ concentrations and followed by a gradual fall for higher concentration. This clearly illustrates that donor addition to antiferroelectric thin films controls the domain switching even under weak fields. (C) 2002 Elsevier Science B.V. All rights reserved.

Modified kinetic flux vector splitting (m-KFVS) method for compressible flows

To resolve many flow features accurately, like accurate capture of suction peak in subsonic flows and crisp shocks in flows with discontinuities, to minimise the loss in stagnation pressure in isentropic flows or even flow separation in viscous flows require an accurate and low dissipative numerical scheme. The first order kinetic flux vector splitting (KFVS) method has been found to be very robust but suffers from the problem of having much more numerical diffusion than required, resulting in inaccurate computation of the above flow features. However, numerical dissipation can be reduced by refining the grid or by using higher order kinetic schemes. In flows with strong shock waves, the higher order schemes require limiters, which reduce the local order of accuracy to first order, resulting in degradation of flow features in many cases. Further, these schemes require more points in the stencil and hence consume more computational time and memory. In this paper, we present a low dissipative modified KFVS (m-KFVS) method which leads to improved splitting of inviscid fluxes. The m-KFVS method captures the above flow features more accurately compared to first order KFVS and the results are comparable to second order accurate KFVS method, by still using the first order stencil. (C) 2011 Elsevier Ltd. All rights reserved.

Defining the ‘modified Griffin plot’ in vortex-induced vibration: revealing the effect of Reynolds number using controlled damping

In the present work, we study the transverse vortex-induced vibrations of an elastically mounted rigid cylinder in a fluid flow. We employ a technique to accurately control the structural damping, enabling the system to take on both negative and positive damping. This permits a systematic study of the effects of system mass and damping on the peak vibration response. Previous experiments over the last 30 years indicate a large scatter in peak-amplitude data ($A^*$) versus the product of mass–damping ($\alpha$), in the so-called ‘Griffin plot’. A principal result in the present work is the discovery that the data collapse very well if one takes into account the effect of Reynolds number ($\mbox{\textit{Re}}$), as an extra parameter in a modified Griffin plot. Peak amplitudes corresponding to zero damping ($A^*_{{\alpha}{=}0}$), for a compilation of experiments over a wide range of $\mbox{\textit{Re}}\,{=}\,500-33000$, are very well represented by the functional form $A^*_{\alpha{=}0} \,{=}\, f(\mbox{\textit{Re}}) \,{=}\, \log(0.41\,\mbox{\textit{Re}}^{0.36}$). For a given $\mbox{\textit{Re}}$, the amplitude $A^*$ appears to be proportional to a function of mass–damping, $A^*\propto g(\alpha)$, which is a similar function over all $\mbox{\textit{Re}}$. A good best-fit for a wide range of mass–damping and Reynolds number is thus given by the following simple expression, where $A^*\,{=}\, g(\alpha)\,f(\mbox{\textit{Re}})$: \[ A^* \,{=}\,(1 - 1.12\,\alpha + 0.30\,\alpha^2)\,\log (0.41\,\mbox{\textit{Re}}^{0.36}). \] In essence, by using a renormalized parameter, which we define as the ‘modified amplitude’, $A^*_M\,{=}\,A^*/A^*_{\alpha{=}0}$, the previously scattered data collapse very well onto a single curve, $g(\alpha)$, on what we refer to as the ‘modified Griffin plot’. There has also been much debate over the last three decades concerning the validity of using the product of mass and damping (such as $\alpha$) in these problems. Our results indicate that the combined mass–damping parameter ($\alpha$) does indeed collapse peak-amplitude data well, at a given $\mbox{\textit{Re}}$, independent of the precise mass and damping values, for mass ratios down to $m^*\,{=}\,1$.

The inactive X chromosome in the human female is enriched in 5-methylcytosine to an unusual degree and appears to contain more of this modified nucleotide than the remainder of the genome

By employing a procedure that combines ELISA and photoacoustic spectroscopy, we have examined the content of 5-methylcytosine (m(5)C) in DNA of individuals who differed from one another in the number of X chromosomes in their genomes. The results show that the human inactive X chromosome (Xi) contains very high amounts of this modified nucleotide. We estimate that in the 46,XX female there is more m(5)C in Xi (similar to3.6 x 10(7)) than in all the remaining chromosomes put together (similar to2.1 x 10(7)). Our results also suggest that nearly one-fifth of all cytosines in Xi are methylated and that, in addition to CpG methylation, there is extensive non-CpG methylation as well.

Development of solidification microstructure in boron-modified alloy Ti-6Al-4V-0.1B

Hypoeutectic boron addition (0.1 wt.%) to Ti-6Al-4V is known to cause significant refinement of the cast microstructure. In the present investigation, it has been observed that trace boron addition to Ti-6Al-4V alloy also ensures excellent microstructural homogeneity throughout the ingot. A subdued thermal gradient, related to the basic grain refinement mechanism by constitutional undercooling, persists during solidification for the boron-containing alloy and maintains equivalent beta grain growth kinetics at different locations in the ingot. The Ti-6Al-4V alloy shows relatively strong texture with preferred components (e.g. ingot axis parallel to[0 0 0 1] or [1 0 (1) over bar 0]) over the entire ingot and gradual transition of texture components along the radius. For Ti-6Al-4V-0.1B alloy, significant weakening characterizes both the high-temperature beta and room-temperature a texture. In addition to solidification factors that are responsible for weak beta texture development, microstructural differences due to boron addition, e.g. the absence of grain boundary alpha phase and presence of TiB particles, strongly affects the mechanism of beta -> alpha phase transformation and consequently weakens the alpha phase texture. Based on the understanding developed for the boron-modified alloy, a novel mechanism has been proposed for the microstructure and texture formation during solidification and phase transformation. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Modified lattice model for mode-I fracture analysis of notched plain concrete beam using probabilistic approach

A modified lattice model using finite element method has been developed to study the mode-I fracture analysis of heterogeneous materials like concrete. In this model, the truss members always join at points where aggregates are located which are modeled as plane stress triangular elements. The truss members are given the properties of cement mortar matrix randomly, so as to represent the randomness of strength in concrete. It is widely accepted that the fracture of concrete structures should not be based on strength criterion alone, but should be coupled with energy criterion. Here, by incorporating the strain softening through a parameter ‘α’, the energy concept is introduced. The softening branch of load-displacement curves was successfully obtained. From the sensitivity study, it was observed that the maximum load of a beam is most sensitive to the tensile strength of mortar. It is seen that by varying the values of properties of mortar according to a normal random distribution, better results can be obtained for load-displacement diagram.

Modified Stability Checking for On-Line Error Detection

The paper propose a unified error detection technique, based on stability checking, for on-line detection of delay, crosstalk and transient faults in combinational circuits and SEUs in sequential elements. The proposed method, called modified stability checking (MSC), overcomes the limitations of the earlier stability checking methods. The paper also proposed a novel checker circuit to realize this scheme. The checker is self-checking for a wide set of realistic internal faults including transient faults. Extensive circuit simulations have been done to characterize the checker circuit. A prototype checker circuit for a 1mm2 standard cell array has been implemented in a 0.13mum process.

Enhancement of charge and energy storage in sol-gel derived pure and La-modified PbZrO3 thin films

Antiferroelectric lanthanum-modified PbZrO3 thin films with La contents between 0 and 6 at. % have been deposited on Pt(111)/Ti/SiO2/Si substrate by sol-gel route. On the extent of La-modification, maximum polarization (Pmax) and recoverable energy density (W) have been enhanced followed by their subsequent reduction. A maximum Pmax ( ∼ 0.54 C/m2 at ∼ 60 MV/m) as well as a maximum W ( ∼ 14.9 J/cc at ∼ 60 MV/m) have been achieved on 5% La modification. Both Pmax and W have been found to be strongly dependent on La-induced crystallographic orientations.