Elastic constants of Ni-Mn-Ga magnetic shape memory alloys

We have measured the adiabatic second order elastic constants of two Ni-Mn-Ga magnetic shape memory crystals with different martensitic transition temperatures, using ultrasonic methods. The temperature dependence of the elastic constants has been followed across the ferromagnetic transition and down to the martensitic transition temperature. Within experimental errors no noticeable change in any of the elastic constants has been observed at the Curie point. The temperature dependence of the shear elastic constant C' has been found to be very different for the two alloys. Such a different behavior is in agreement with recent theoretical predictions for systems undergoing multi-stage structural transitions.

Comment on "Reappraisal of experimental values of third-order elastic constants of some cubic semiconductors and metals"

In a recent paper A. S. Johal and D. J. Dunstan [Phys. Rev. B 73, 024106 (2006)] have applied multivariate linear regression analysis to the published data of the change in ultrasonic velocity with applied stress. The aim is to obtain the best estimates for the third-order elastic constants in cubic materials. From such an analysis they conclude that uniaxial stress data on metals turns out to be nearly useless by itself. The purpose of this comment is to point out that by a proper analysis of uniaxial stress data it is possible to obtain reliable values of third-order elastic constants in cubic metals and alloys. Cu-based shape memory alloys are used as an illustrative example.

Temperature and magnetic-field dependence of the elastic constants of Ni-Mn-Al magnetic Heusler alloy

We report on measurements of the adiabatic second-order elastic constants of the off-stoichiometric Ni54Mn23Al23 single-crystalline Heusler alloy. The variation in the temperature dependence of the elastic constants has been investigated across the magnetic transition and over a broad temperature range. Anomalies in the temperature behavior of the elastic constants have been found in the vicinity of the magnetic phase transition. Measurements under applied magnetic field, both isothermal and variable temperature, show that the value of the elastic constants depends on magnetic order, thus giving evidence for magnetoelastic coupling in this alloy system.

Curing studies of elastomer blends with special reference to NR/ NBR and NR/BR blends

There are a large number of commercial examples and property advantages of immiscible elastomer blends.73 Blends of natural rubber (NR) and polybutadiene (BR) have shown various advantages including heat stability, improved elasticity and abrasion resistance. Ethylene-propylene-diene-rubber (EPDM) blended with styrene-butadiene rubber (SBR) has shown improvements in ozone and chemical resistance with better compression set properties. Blends of EPDM and nitrile rubber (NBR) have been cited as a compromise for obtaining moderate oil and ozone resistance with improved low temperature properties. Neoprene (CR)/BR blends offer improved low temperature properties and abrasion resistance with better processing characteristics etc. However, in many of the commercial two-phase elastomer blends, segregation of the crosslinking agents, carbon black or antioxidants preferentially into one phase can result in failure to attain optimum properties. Soluble and insoluble compounding ingredients are found to be preferentially concentrated in one phase. The balance of optimum curing of both phases therefore presents a difficult problem. It has been the aim of this study to improve the performance of commercially important elastomer blends such as natural rubber (NR)/styrene-butadiene rubber (SBR) and natural rubber/polybutadiene rubber (BR) by industrially viable procedures

Studies on L-glutamic acid Production using Brevibacterium sp.

The thesis comprises a set of experiments mainly focused on the improvement of L-glutamic acid fennentation. Much attention has been given to use of locally available raw materials, culturing the organism on inert solid substrates and also immobilization of the bacterial cells from the view point of long term utilization of biocatalyst and continuous operation of the stabilized system. Studies were also carried out for the down stream processing for the extraction and purification of L-glutamic acid. An attempt was made to study the morphological features of the microorganism including the cell premeability. In relation with the accumulation of glutamic acid within the cells an approach was made to study the behaviour of the Brevibacterium cells when they are exposed to hyper osmotic environment. Attempts were also made to study the requirement of iron and production of siderophores by this microbial strain. The search for a suitable nitrogen source for glutamate fermentation ended with a promising result that they got a potent urease activity and it can be utilized for many biotransfonnation studies. The entire thesis is presented in three sections, viz. introductory section, experimental section and the concluding section

Depinning transition of dislocation assemblies: Pileups and low-angle grain boundaries

We investigate the depinning transition occurring in dislocation assemblies. In particular, we consider the cases of regularly spaced pileups and low-angle grain boundaries interacting with a disordered stress landscape provided by solute atoms, or by other immobile dislocations present in nonactive slip systems. Using linear elasticity, we compute the stress originated by small deformations of these assemblies and the corresponding energy cost in two and three dimensions. Contrary to the case of isolated dislocation lines, which are usually approximated as elastic strings with an effective line tension, the deformations of a dislocation assembly cannot be described by local elastic interactions with a constant tension or stiffness. A nonlocal elastic kernel results as a consequence of long-range interactions between dislocations. In light of this result, we revise statistical depinning theories of dislocation assemblies and compare the theoretical results with numerical simulations and experimental data.

Grain boundaries in vortex matter

We explore the statistical properties of grain boundaries in the vortex polycrystalline phase of type-II superconductors. Treating grain boundaries as arrays of dislocations interacting through linear elasticity, we show that self-interaction of a deformed grain boundary is equivalent to a nonlocal long-range surface tension. This affects the pinning properties of grain boundaries, which are found to be less rough than isolated dislocations. The presence of grain boundaries has an important effect on the transport properties of type-II superconductors as we show by numerical simulations: our results indicate that the critical current is higher for a vortex polycrystal than for a regular vortex lattice. Finally, we discuss the possible role of grain boundaries in vortex lattice melting. Through a phenomenological theory we show that melting can be preceded by an intermediate polycrystalline phase.

Photometric and fundamental plane studies of galaxies

Determining the morphological parameters that describe galaxies has always been a challenging task. The studies on the correlations between different photometric as well as spectroscopic parameters of the galaxies help in understanding their structure, properties of the stars and gas which constitute the galaxy, the various physical and chemical processes which determine the properties, and galaxy formation and evolution. In the last few decades, the advent of Charge Coupled Devices (CCDs) and near infrared arrays ha\·e provided quick and reliable digitized data acquisition, in the optical and near infrared bands. This has provided an avalanche of data, which can be processed using sophisticated image analysis techniques to obtain information about the morphology of galaxies. The photometric analysis performed in this thesis involve the extraction of structural parameters of early type gala.xies imaged in the near infrared K (2.2ttm) band, obtaining correlations between these, parameters and using them to constrain the large scale properties of galaxi,~s.

Prediction of Learning Disabilities in School Age Children using SVM and Decision Tree

This paper highlights the prediction of Learning Disabilities (LD) in school-age children using two classification methods, Support Vector Machine (SVM) and Decision Tree (DT), with an emphasis on applications of data mining. About 10% of children enrolled in school have a learning disability. Learning disability prediction in school age children is a very complicated task because it tends to be identified in elementary school where there is no one sign to be identified. By using any of the two classification methods, SVM and DT, we can easily and accurately predict LD in any child. Also, we can determine the merits and demerits of these two classifiers and the best one can be selected for the use in the relevant field. In this study, Sequential Minimal Optimization (SMO) algorithm is used in performing SVM and J48 algorithm is used in constructing decision trees.

Morphological filtering on hypergraphs

The focus of this article is to develop computationally efficient mathematical morphology operators on hypergraphs. To this aim we consider lattice structures on hypergraphs on which we build morphological operators. We develop a pair of dual adjunctions between the vertex set and the hyper edge set of a hypergraph H, by defining a vertex-hyperedge correspondence. This allows us to recover the classical notion of a dilation/erosion of a subset of vertices and to extend it to subhypergraphs of H. Afterward, we propose several new openings, closings, granulometries and alternate sequential filters acting (i) on the subsets of the vertex and hyperedge set of H and (ii) on the subhypergraphs of a hypergraph

Mechanical Properties of Steel Fiber-Reinforced Concrete

This paper presents the results from an experimental program and an analytical assessment of the influence of addition of fibers on mechanical properties of concrete. Models derived based on the regression analysis of 60 test data for various mechanical properties of steel fiber-reinforced concrete have been presented. The various strength properties studied are cube and cylinder compressive strength, split tensile strength, modulus of rupture and postcracking performance, modulus of elasticity, Poisson’s ratio, and strain corresponding to peak compressive stress. The variables considered are grade of concrete, namely, normal strength 35 MPa , moderately high strength 65 MPa , and high-strength concrete 85 MPa , and the volume fraction of the fiber Vf =0.0, 0.5, 1.0, and 1.5% . The strength of steel fiber-reinforced concrete predicted using the proposed models have been compared with the test data from the present study and with various other test data reported in the literature. The proposed model predicted the test data quite accurately. The study indicates that the fiber matrix interaction contributes significantly to enhancement of mechanical properties caused by the introduction of fibers, which is at variance with both existing models and formulations based on the law of mixtures

Strength and serviceability performance of beams reinforced with GFRP bars in flexure

Glass fiber reinforced polymer (GFRP) rebars have been identified as an alternate construction material for reinforcing concrete during the last decade primarily due to its strength and durability related characteristics. These materials have strength higher than steel, but exhibit linear stress–strain response up to failure. Furthermore, the modulus of elasticity of GFRP is significantly lower than that of steel. This reduced stiffness often controls the design of the GFRP reinforced concrete elements. In the present investigation, GFRP reinforced beams designed based on limit state principles have been examined to understand their strength and serviceability performance. A block type rotation failure was observed for GFRP reinforced beams, while flexural failure was observed in geometrically similar control beams reinforced with steel rebars. An analytical model has been proposed for strength assessment accounting for the failure pattern observed for GFRP reinforced beams. The serviceability criteria for design of GFRP reinforced beams appear to be governed by maximum crack width. An empirical model has been proposed for predicting the maximum width of the cracks. Deflection of these GFRP rebar reinforced beams has been predicted using an earlier model available in the literature. The results predicted by the analytical model compare well with the experimental data

Properties of Equilibrium Distributions of Order n

The present work is intended to discuss various properties and reliability aspects of higher order equilibrium distributions in continuous, discrete and multivariate cases, which contribute to the study on equilibrium distributions. At first, we have to study and consolidate the existing literature on equilibrium distributions. For this we need some basic concepts in reliability. These are being discussed in the 2nd chapter, In Chapter 3, some identities connecting the failure rate functions and moments of residual life of the univariate, non-negative continuous equilibrium distributions of higher order and that of the baseline distribution are derived. These identities are then used to characterize the generalized Pareto model, mixture of exponentials and gamma distribution. An approach using the characteristic functions is also discussed with illustrations. Moreover, characterizations of ageing classes using stochastic orders has been discussed. Part of the results of this chapter has been reported in Nair and Preeth (2009). Various properties of equilibrium distributions of non-negative discrete univariate random variables are discussed in Chapter 4. Then some characterizations of the geo- metric, Waring and negative hyper-geometric distributions are presented. Moreover, the ageing properties of the original distribution and nth order equilibrium distribu- tions are compared. Part of the results of this chapter have been reported in Nair, Sankaran and Preeth (2012). Chapter 5 is a continuation of Chapter 4. Here, several conditions, in terms of stochastic orders connecting the baseline and its equilibrium distributions are derived. These conditions can be used to rede_ne certain ageing notions. Then equilibrium distributions of two random variables are compared in terms of various stochastic orders that have implications in reliability applications. In Chapter 6, we make two approaches to de_ne multivariate equilibrium distribu- tions of order n. Then various properties including characterizations of higher order equilibrium distributions are presented. Part of the results of this chapter have been reported in Nair and Preeth (2008). The Thesis is concluded in Chapter 7. A discussion on further studies on equilib- rium distributions is also made in this chapter.

Export performancecof Indian spices in the WTO regime: a disaggregated analysis

Export has assumed an important place in the development of any country and considered as the engine of economic growth. India requires huge amount of foreign exchange for its essential import and for achieving rapid growth. Millions of job opportunities have to be created to utilise the youth for nation building. Even though the country has different sources of foreign exchange, export earning is the safe way of obtaining it in the long run. Export of high valued traditional products not only gives foreign exchange, but also employment to large number of people. Spices are the traditional products of India whose production process is highly intensive in semi and unskilled labour, and high domestic and foreign market prices compared to other traditional products. The new world trade scenario with the establishment of WTO has affected India’s spices export considerably. The study examines the export performance of Indian spices in the WTO regime taking the export of major spices from 1985 to 2013 using the growth of export, trend and instability in growth rate, changes in the composition and direction of spices, export performance ratio and the prospects of spices in earning foreign exchange during the WTO period and Pre-WTO period. The analysis reveals that the overall performance of Indian spices exports during the WTO regime are satisfactory. Export volume and value increased much during this period. But the decrease in market share of spices export during the WTO period reflects that, the favourable conditions in the international market are not exploited by India. High Revealed Comparative Advantage (RCA) and Value Elasticity (EV) of major spices amidst the low export shares shows that export performance of Indian spices during the WTO regime was not mainly affected by external demand factors as suggested by Ragnar Nurkse in his Demand Deficiency Thesis, but because of internal supply factors as suggested in Supply Deficiency Thesis, (supported by K.S Dhinsha, Dacosta, Goddamwar,etc.). But the fluctuations of export during the recession and prosperity periods show that external demand is also a determinant of Indian spices export. From this one can conclude that both the domestic supply factors and foreign demand factors influence the export performance of Indian spices. The long term performance of Indian spices exports are mainly influenced by domestic supply factors as suggested by Supply Deficiency Thesis and short term performance is mostly influenced by external demand factors as suggested by Demand Deficiency Thesis.