P. Anand

Laboratory Study on Moisture Susceptibility of Dense Graded Mixes

Moisture damage is the degradation of the mechanical properties of the material attributable to the presence of moisture in its microstructure. To enhance the life of bituminous pavements, it is necessary to understand moisture’s damage on pavements and to evaluate the effects of hydrated lime as moisture damage resisting agents. The basis of laboratory work was AASHTO T 283 test and it was performed on two types of dense graded bituminous mixes that included dense bituminous macadam and bituminous concrete mix. The study was carried out for mixes prepared without lime, and the same process was repeated with addition of 2% quantity of hydrated lime. The addition of hydrated lime in the asphalt mix improves the tensile strength ratio. However, a well-controlled lime treatment is required to maximize distribution and dispersion of lime particles on aggregate surfaces. This study also presents various causes of moisture damage and their mechanisms. Attention is also given to the chemical and mineralogical composition of aggregates and effect of some important minerals on moisture susceptibility of aggregates.

Coastal upwelling off the southwest coast of India: observations and simulations

ABSTRACT Spatial hydrographic data collected from August 2007 through May 2008 and the Princeton Ocean Model (POM) are utilized to explain and document the upwelling in the south eastern Arabian Sea (SEAS). The decrease in the magnitude of winds towards the coast favors local anti-cyclonic vorticity, resulting in the formation of cyclonic eddy and reversal of coastal currents. The Ekman transport due to alongshore winds, Ekman pumping due to wind stress curl, cyclonic eddy and southward West Indian Coastal Currents play different roles in the SEAS upwelling. In the offshore, wind stress curl leads to the formation of meso-scale eddies, resulting in Ekman pumping at the center and consequent upwelling. The rapid depth variation on the western side of Quilon Mount intensifies upwelling in the offshore. The upwelling Kelvin waves generated at the equator terminates in the Bay of Bengal and do not contribute to the SEAS upwelling. The possible role of local and remote winds, especially around Sri Lanka on the upwelling dynamics of SEAS is described utilizing POM. The Kelvin waves generated off the coast of Sri Lanka during the active phase of the summer monsoon also contribute to the upwelling dynamics off the west coast of India.

Observation of switching between SA and RSA in silver/goldpolyaniline nanocomposite films

In the present work, attempts have been made to embed Silver (Ag) /Gold (Au) - nanoparticles into polyaniline (PANI) matrix using an easy wet chemical route. It is expected that the resulting nanocomposite will show the interesting third order nonlinear optical characteristics of Ag/Au-nanoparicles modified by the advantageous properties of the conducting polymer PANI. Structural characterisation of Ag/Au-PANI nanocomposite samples was done using X-ray diffraction and Raman studies. UV-visible absorption spectra show the presence of surface plasmon resonance (SPR) peaks centred at 410 nm and 520 nm for Ag-PANI and Au-PANI nanocomposite films respectively, which is a signature of nano dimensionality of the composite samples. Third order nonlinear behaviour of the nanocomposite films was analysed using Z Scan technique employing the second harmonic output (532 nm) of a Q-switched Nd:YAG laser (Minilite, Continuum). It is seen that Ag/Au-PANI nanocomposite film samples show simultaneous presence of saturable absorption (SA) and reversible saturable absorptions (RSA) behaviour at 50 μJ laser excitation. This switching between SA and RSA has been reported in many metal nanocomposite systems. However similar behavior in nanocomposite film samples has not been pursued much. The highlight of the present work is the observation of the switching between SA and RSA in Ag/Au polyaniline nanocomposite films. The switching behavior can be ascribed to the interplay between ground state plasmon band bleaching and excited state absorption. Two photon assisted absorption has been identified as the prime factor contributing towards the observed RSA in these nanocomposite films.

On the structural and impedance characteristics of Li- doped PEO, using n-butyl lithium in hexane as dopant

Nowadays polymer based solid state electrolytes for applications in rechargeable battery systems are highly sought after materials, pursued extensively by various research groups worldwide. Numerous methods are discussed in literature to improve the fundamental properties like electrical conductivity, mechanical stability and interfacial stability of polymer based electrolytes. The application of these electrolytes in Li-ion cells is still in the amateur state, due to low ionic conductivity, low lithium transport number and the processing difficulties. The present work is an attempt to study the effects of Li doping on the structural and transport properties of the polymer electrolyte, poly-ethelene oxide (PEO) (Molecular weight: 200,000). Li doped PEO was obtained by treating PEO with n-Butyllithium in hexane for different doping concentrations. Structural characterization of the samples was done by XRD and FTIR techniques. Impedance measurements were carried out to estimate the ionic conductivity of Li ...

A software to merge temperature and salinity profiles with climatology

Temperature and salinity are two major parameters deciding the characteristics of the ocean water column. Accurate information of these parameters is always a pre-requisite for any study of major climatic/physical processes. The insitu measurement of these parameters is done using instruments such as XBT, XCTD and CTD. Most of the instances, the data will not be collected upto the bottom depth due to instrument or time limitations. In such cases, the collected profiles are artificially extended up to ocean bottom, which is not always true. A better option is to extract the profile upto bottom by blending the insitu profile with climatology. The Profile blending software, written in Visual Basic, is for merging real time insitu temperature and salinity profiles with the climatology profiles for providing the data from surface to bottom. This s/w provides a smoother transition of gradient across the merge point without disturbing the insitu data. It also provides the climatological salinity profile for the corresponding near real time temperature profile obtained from expendable bathythermograph (XBT) records.