On the crystallization kinetics and micro-structural transformations of Fe40Ni38B18Mo4 alloys

Activation energy for crystallization (Ec) is a pertinent parameter that decides the application potential of many metallic glasses and is proportional to the crystallization temperature. Higher crystallization temperatures are desirable for soft magnetic applications, while lower values for data storage purposes. In this investigation, from the heating rate dependence of peak crystallization temperature Tp, the Ec values have been evaluated by three different methods for metglas 2826 MB (Fe40Ni38B18Mo4) accurately. The Ec values are correlated with the morphological changes, and the structural evolution associated with annealing temperatures is discussed.

Microwave exfoliated reduced graphene oxide epoxy nanocomposites for high performance applications

Graphene has captured the attention of scientific community due to recently emerging high performance applications. Hence, studying its reinforcing effects on epoxy resin is a significant step. In this study, microwave exfoliated reduced graphene oxide (MERGO) was prepared from natural graphite for subsequent fabrication of epoxy nanocomposites using triethylenetetramine (TETA) as a curing agent via insitu polymerization. Thermogravimetric analysis (TGA), X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), C13 NMR spectroscopy, X-ray photoelectron spectroscopy (XPS) and ultravioletevisible (UVevis) spectroscopy were employed to confirm the simultaneous reduction and exfoliation of graphene oxide. The reinforcing effect of MERGO on epoxy resin was explored by investigating its static mechanical properties and dynamic mechanical analysis (DMA) at MERGO loadings of 0 to 0.5 phr. The micro-structure of epoxy/MERGO nanocomposites was investigated using scanning electron microscope (SEM), transmission electron microscope (TEM) and XRD techniques. The present work reports an enhancement of 32%, 103% and 85% in tensile, impact and flexural strength respectively of epoxy by the addition of even 0.25 phr MERGO. At this loading elastic and flexural moduli also increased by 10% and 65%, respectively. Single-edge-notch three-point-Bending (SEN-TPB) fracture toughness (KIC) measurements were carried out where a 63% increase was observed by the introduction of 0.25 phr MERGO. The interfacial interactions brought about by graphene also benefited the dynamic mechanical properties to a large extent in the form of a significant enhancement in storage modulus and slightly improved glass transition temperature. Considerable improvements were also detected in dielectric properties. The epoxy nanocomposite also attained an ac conductivity of 10 5 S/m and a remarkable increase in dielectric constant. The simple and cost effective way of graphene synthesis for the fabrication of epoxy/MERGO nanocomposites may be extended to the preparation of other MERGO based polymer nanocomposites. This remarkable class of materials has thrown open enormous opportunities for developing conductive adhesives and in microelectronics

Dynamic and Thermodynamic Structure of the Monsoon Boundary Layer over India

The objective of the study is to examine the dynamic and thermodynamic structure and the variations that occur in the surface layer during the pre-monsoon, onset and post-monsoon periods over the Indian region. The variations caused during the occurrence of micro and mesoscale systems, structure and variation in the marine boundary layer over the Indian region is also investigated. The drag coefficient computed indirectly also shows variation during various seasons. The thermodynamic structure of the atmosphere shows variation during the various seasons. The onset monsoon causes lowering of the Lifting Condensation Levels. The outcome of the study is expected to provide a better understanding of the structure and variations in the boundary layer over India, which is useful for many applications especially for numerical modeling studies.

Diversification In Employment Structure And Status Of Rural Women Workers In Ernakulam District

The basic objective of the present study has been to observe the process and pattern of employment diversification among the rural women workers in Ernakulam district. The evidences are that the women workers in the rural areas of the state are being increasingly diversified into the tertiary sector. The clear cut evidence for the fact that in Kerala non-agricultural employment of rural women is increasing with more and more of them getting diversified into the tertiary sector. The women get more self esteem and recognition in terms of the work being done by them. In the urban areas of the state as a poverty eradicating measure the Kerala government has already introduced a new scheme under the banner of Kudumbasree. Another fact noticed in the study that the sectoral shift of women workers has posed a grave problem to the agricultural sector. The reluctance of workers to do manual jobs on land and the prevalence of high wages among the agricultural labours has left many a cultivable area fallow or has induced farmers to shift to less labour –intensive crops. The situation is expected to worsen in future as even the high wages fail to attract the young generation to this sector. To conclude the study has fulfilled all its objectives, viz; highlighting the rural employment structure in Kerala, examining the process, pattern, determinants and consequences of diversification among rural women workers in the sample villages. Being the first of its kind at the micro level in the state it contributes to the available literature in the area enriching the database that is crucially lacking for devising projects at the village and block-level. There exists ample scope for future research of similar nature in an urban background where the secondary data-sources are hinding towards a reversal of trends from non-agriculture to agriculture.

Influvence of Alloying Additions on the Structure and Properties of Ai-7Si-0.3Mg Alloy

Cast Ai-Si alloys are widely used in the automotive, aerospace and general engineering industries due to their excellent combination of properties such as good castability, low coefficient of thermal expansion, high strength-to-weight ratio and good corrosion resistance. The present investigation is on the influence of alloying additions on the structure and properties of Ai-7Si-0.3Mg alloy. The primary objective of this present investigation is to study these beneficial effects of calcium on the structure and properties of Ai-7Si-0.3Mg-xFe alloys. The second objective of this work is to study the effects of Mn,Be and Sr addition as Fe neutralizers and also to study the interaction of Mn,Be,Sr and Ca in Ai-7Si-0.3Mg-xFe alloys. In this study the duel beneficial effects of Ca viz;modification and Fe-neutralization, comparison of the effects of Ca and Sr with common Fe neutralizers. The casting have been characterized with respect to their microstructure, %porosity and electrical conductivity, solidification behaviour and mechanical properties. One of the interesting observations in the present work is that a low level of calcium reduces the porosity compared to the untreated alloy. However higher level of calcium addition lead to higher porosity in the casting. An empirical analysis carried out for comparing the results of the present work with those of the other researchers on the effect of increasing iron content on UTS and % elongation of Ai-Si-Mg and Ai-Si-Cu alloys has shown a linear and an inverse first order polynomial relationships respectively.

Numerical Investigations on Soil Structure Interaction of Multistorey Frames

Frames are the most widely used structural system for multistorey buildings. A building frame is a three dimensional discrete structure consisting of a number of high rise bays in two directions at right angles to each other in the vertical plane. Multistorey frames are a three dimensional lattice structure which are statically indeterminate. Frames sustain gravity loads and resist lateral forces acting on it. India lies at the north westem end of the Indo-Australian tectonic plate and is identified as an active tectonic area. Under horizontal shaking of the ground, horizontal inertial forces are generated at the floor levels of a multistorey frame. These lateral inertia forces are transferred by the floor slab to the beams, subsequently to the columns and finally to the soil through the foundation system. There are many parameters that affect the response of a structure to ground excitations such as, shape, size and geometry of the structure, type of foundation, soil characteristics etc. The Soil Structure Interaction (SS1) effects refer to the influence of the supporting soil medium on the behavior of the structure when it is subjected to different types of loads. Interaction between the structure and its supporting foundation and soil, which is a complete system, has been modeled with finite elements. Numerical investigations have been carried out on a four bay, twelve storeyed regular multistorey frame considering depth of fixity at ground level, at characteristic depth of pile and at full depth. Soil structure interaction effects have been studied by considering two models for soil viz., discrete and continuum. Linear static analysis has been conducted to study the interaction effects under static load. Free vibration analysis and further shock spectrum analysis has been conducted to study the interaction effects under time dependent loads. The study has been extended to four types of soil viz., laterite, sand, alluvium and layered.The structural responses evaluated in the finite element analysis are bending moment, shear force and axial force for columns, and bending moment and shear force for beams. These responses increase with increase in the founding depth; however these responses show minimal increase beyond the characteristic length of pile. When the soil structure interaction effects are incorporated in the analysis, the aforesaid responses of the frame increases upto the characteristic depth and decreases when the frame has been analysed for the full depth. It has been observed that shock spectrum analysis gives wide variation of responses in the frame compared to linear elastic analysis. Both increase and decrease in responses have been observed in the interior storeys. The good congruence shown by the two finite element models viz., discrete and continuum in linear static analysis has been absent in shock spectrum analysis.

“Effects of monospecific and mixed algal diets on survival, development and biochemical composition of Penaeus monodon larvae”

The main objective of the present work is to acquire information regarding the growth responses of P. monodon larvae (from PZ1 upto PL1) to various mono specific and mixed diets. Evaluate the nutritional quality of selected species of micro algae viz. Chaetoceros calcitrans, Dunaliella salina, Isochrysis galbana and Nannochloropsis salina, larvae at three cell concentrations 10x104 cells/ml, 25x104 cells/ml and 50x104 cells/ml. The P. monodon larvae were transported, at the Nauplius stage, to the laboratory. The larvae were stocked at density of 150 larvae per litre in 5 litre FRP tanks with 3 litres of sea water. The algal cell density given to the larvae varied. The larval stages were fed with increasing densities of algae to evaluate the relationship between the food densities, ingestion rates, development and growth of the larvae. The water quality parameters, the percentage of survival rate, the growth estimation and the algal cell count were done. Each experiment was carried out in triplicate with a control group of larvae fed with Chaetoceros calcitrans. For the estimation standard procedures were used.to P. monodon

Finite size effects on the structural and magnetic properties of sol–gel synthesized NiFe2O4 powders

Nanoparticles of nickel ferrite have been synthesized by the sol–gel method and the effect of grain size on its structural and magnetic properties have been studied in detail. X-ray diffraction (XRD) studies revealed that all the samples are single phasic possessing the inverse spinel structure. Grain size of the sol–gel synthesized powders has been determined from the XRD data and the strain graph. A grain size of 9 nm was observed for the as prepared powders of NiFe2O4 obtained through the sol–gel method. It was also observed that strain was induced during the firing process. Magnetization measurements have been carried out on all the samples prepared in the present series. It was found that the specific magnetization of the nanosized NiFe2O4 powders was lower than that of the corresponding coarse-grained counterparts and decreased with a decrease in grain size. The coercivity of the sol–gel synthesized NiFe2O4 nanoparticles attained a maximum value when the grain size was 15nm and then decreased as the grain size was increased further.

Finite size effects on the electrical properties of sol–gel synthesized CoFe2O4 powders: deviation from Maxwell–Wagner theory and evidence of surface polarization effects

Fine particles of cobalt ferrite were synthesized by the sol–gel method. Subsequent heat treatment at different temperatures yielded cobalt ferrites having different grain sizes. X-ray diffraction studies were carried out to elucidate the structure of all the samples. Dielectric permittivity and ac conductivity of all the samples were evaluated as a function of frequency, temperature and grain size. The variation of permittivity and ac conductivity with frequency reveals that the dispersion is due to Maxwell–Wagner type interfacial polarization in general, with a noted variation from the expected behaviour for the cold synthesized samples. High permittivity and conductivity for small grains were explained on the basis of the correlated barrier-hopping model