Publication10

Here we report orientational dynamics in monolayer protected metal-cluster (MPC) systems as studied by quasielastic neutron scattering (QENS) technique. Experiments carried out using two different instruments having very different energy windows, thus covering a time scale of 10-9-10-12 s. Clear evidence of absence of 'rotator phase' has been found in isolated MPCs (Au-SC18H37, Au-SC8H17 and Au-SC6H13), a superlattice MPC (Ag-SC18H37) as well as planar thiolates (Ag-SC6H13, Ag-SC12H25, Ag-SC18H37) at room temperature. However, dynamics were found to evolve on increase of temperature and its behaviour is found to be different in the superlattice and isolated cluster systems. Detailed dynamical informations for MPCs are obtained for the first time in these systems. © 2003 Elsevier Science B.V. All rights reserved.

The diffuse surface reflectance profiles of the goat's isolated heart, spleen, and adipose tissues by multiprobe laser reflectometer are measured. The normalized backscattered intensity values for adipose, heart, and spleen tissues at source-detector separation 0.2 cm, are 0.060, 0.021, and 0.003, respectively. The optical parameters of these tissues are determined by the best fit (χ0.992) of their spatial profiles with that as obtained by Monte Carlo simulation by iterative procedure. As the optical parameters of these vary over a wide range, adipose and spleen tissues are treated as inhomogeneity of diameter 0.1, 0.2, or 0.3 cm, and placed inside the control (heart) tissue at different depths. Anisotropic simulation of light backscattering or photon depth distribution is significantly different for various tissues. The surface intensity profiles vary depending on the changes in tissue composition. From the horizontal scans of the subtracted images, the photon backscattering simulated images of control and combination of tissues are obtained. By analysis of peak intensity and full-width at half maximum, the type, location, and size of the tissue compositional variation are determined.

It is indicated in the literature that the toe geometry affects the fatigue properties of butt welded joints in structural steels. In an attempt to study the above effect with respect to stainless steel sheet metal welded joints, butt welded joints having two bead geometries were fabricated using AISI 304L stainless steel using gas tungsten arc welding and gas metal arc welding processes. The objective of the present work was to predict the fatigue life of AISI 304L butt joints failing at the weld toe, using a local stress approach (a two stage model). The notch root stress method was applied to calculate the fatigue crack initiation life, whereas the fatigue crack propagation life was estimated using fracture mechanics concepts. Constant amplitude fatigue tests with a stress ratio R=0 were carried out using a 100 kN servohydraulic Dartec universal testing machine at a frequency of 30 Hz. The crack initiation points were determined using strain gauges, and crack propagation gauges were used to obtain the crack propagation data during the fatigue process. The predicted lives were compared with the experimental values. © 2005 IoM Communications Ltd.

With the advancement of the tools for the analysis of reinforced concrete structures, a proper understanding of the applicability and limitations of the constitutive models has become imperative. This paper lists some of the models that are used for plain and reinforced concrete. The models are presented according to the states of uniaxial, biaxial and triaxial stresses. For reinforced concrete panel elements subjected to shear, models incorporating the softening of concrete compressive stress and the Poisson's effect in the steel tensile stress, are emphasised.

In this article, the selection of process parameters for obtaining a sound weld with an optimal weld strength in the Tungsten Inert Gas (TIG) welding of iron powder metallurgical (P/M) preforms with wrought copper is presented. The quality of the continuous current TIG weldments mainly depends on heat input and in the present case it also depends on the density of the P/M preforms. To consider these quality characteristics together in the selection of process parameters, the modified Taguchi method is adopted to analyze the effect of each parameter on the soundness of the weld, and also to determine the process parameters with optimal weld strength. Experimental results are provided to illustrate the approach.