Non-Destructive Evaluation—A Pivotal Technology for Qualification of Composite Aircraft Structures

Tremendous advances in composite materials and a deeper understanding of their behavior have been responsible for the increased use of composites in the development of advanced, new generation civil and military aircraft. Composites play an important role in any aircraft development programme and are strong contenders to their metal counterparts due to their significant contributions towards improving strength, stiffness, fatigue properties & weight reduction. As materials, structural design & processing have evolved, strong emphasis is placed on effective & reliable damage detection, durability and damage tolerance. As a consequence, Non-destructive Evaluation (NDE) has also undergone significant advances towards meeting the growing demands of quality assurance. Advanced Composites Division (ACD) of National Aerospace Laboratories (NAL), has been involved in the development of composite structures for both civil and military aircraft for over a decade and a half. Innovative composite processing methods like co-curing/co-bonding have been successfully employed to realize airworthy structures. The role of NDE in the development of these structures has been critical and not limited to damage detection alone. On several occasions, NDE has provided valuable inputs towards improving design and process parameters. In-spite of the complexity of the structures, stringent quality requirements and tight delivery schedules, NDE has been successful in certifying these composite structures for airworthiness. This paper discusses the implementation of key NDE techniques like ultrasonics, radiography, acoustic emission and thermography for reliable flaw detection, characterization and quality assurance of composite aircraft structures

Spin Freezing in the Spin Liquid Compound FeAl2O4

Spin freezing in the $A$-site spinel FeAl$_2$O$_4$ which is a spin liquid candidate is studied using remnant magnetization and nonlinear magnetic susceptibility and isofield cooling and heating protocols. The remnant magnetization behavior of FeAl$_2$O$_4$ differs significantly from that of a canonical spin glass which is also supported by analysis of the nonlinear magnetic susceptibility term $\chi_3 (T)$. Through the power-law analysis of $\chi_3 (T)$, a spin-freezing temperature, $T_g$ = 11.4$\pm$0.9~K and critical exponent, $\gamma$ = 1.48$\pm$0.59 are obtained. Cole-Cole analysis of magnetic susceptibility shows the presence of broad spin relaxation times in FeAl$_2$O$_4$, however, the irreversible dc susceptibility plot discourages an interpretation based on conventional spin glass features. The magnetization measured using the cooling-and-heating-in-unequal-fields protocol brings more insight to the magnetic nature of this frustrated magnet and reveals unconventional glassy behaviour. Combining our results, we arrive at the conclusion that the present sample of FeAl$_2$O$_4$ consists of a majority spin liquid phase with "glassy" regions embedded.Comment: 5 pages, 6 figs, 2-column, Accepted to Phys. Rev.

Impact of different tillage methods on growth, development and productivity of maize (Zea mays)-wheat (Tritcum aestivum) cropping system

An experiment was conducted on a silty clay loam soil of Palampur during 2009–2011, to study the effect of different tillage methods in maize (Zea mays L.) wheat {Triticum aestivum (L.) emend. Fiori & Paol.} cropping system. Results revealed that in maize crop, tillage methods in kharif season resulted in significantly highest emergence count (27.1 plant/m2) under manual seed drill. While, multi-crop planter recorded in significantly taller plants (55.4 cm) at 30 DAS; higher dry matter accumulation 81.0, 990.0 and 4184.4 g/m2 at 30, 60 and 90 DAS, respectively and CGR (30.3 g/day/m2) at 30-60 DAS. Tillage methods in rabi season resulted in higher emergence count (17.6 plant/m2) under zero tillage. This treatment also recorded advanced emergence by 1.2 to 1.5 days. In wheat crop, tillage methods in kharif season resulted in significantly highest emergence count (307.6 plant/m2), taller plants (13.1 cm) at 30 DAS, dry matter accumulation (625.3 g/m2) at 120 DAS and CGR (14.4 g/day/m2) at 90-120 DAS under conventional tillage. While, tillage methods in rabi season resulted in significantly highest emergence count (369.5 plants/m2), tallest plants (17.7, 92.6 and 101.0 cm at 60, 120 and at harvest, respectively) with multi-crop planter. While, zero tillage recorded significantly higher CGR (15.8 g/day/m2) and RGR (0.027 g/g/day) during 120-harvest stage. Zero tillage produced statistically at par crop yield and rainwater-use efficiency of both crops with other tillage treatments. Hence, zero tillage can be as good as other intensive tillage system besides lower input cost and environmental security

Double-phase transition and giant positive magnetoresistance in the quasi-skutterudite Gd3_3Ir4_4Sn13_{13}

The magnetic, thermodynamic and electrical/thermal transport properties of the caged-structure quasi-skutterudite Gd$_3$Ir$_4$Sn$_{13}$ are re-investigated. The magnetization $M(T)$, specific heat $C_p(T)$ and the resistivity $\rho(T)$ reveal a double-phase transition -- at $T_{N1}\sim$ 10~K and at $T_{N2}\sim$ 8.8~K -- which was not observed in the previous report on this compound. The antiferromagnetic transition is also visible in the thermal transport data, thereby suggesting a close connection between the electronic and lattice degrees of freedom in this Sn-based quasi-skutterudite. The temperature dependence of $\rho(T)$ is analyzed in terms of a power-law for resistivity pertinent to Fermi liquid picture. Giant, positive magnetoresistance (MR) $\approx$ 80$\%$ is observed in Gd$_3$Ir$_4$Sn$_{13}$ at 2~K with the application of 9~T. The giant MR and the double magnetic transition can be attributed to the quasi-cages and layered antiferromagnetic structure of Gd$_3$Ir$_4$Sn$_{13}$ vulnerable to structural distortions and/or dipolar or spin-reorientation effects. The giant value of MR observed in this class of 3:4:13 type alloys, especially in a Gd-compound, is the highlight of this work.Comment: 20 pages single column, 7 figures, 1 table; Accepted to J. Appl. Phys., 201

On the polar decomposition of right linear operators in quaternionic Hilbert spaces

In this article we prove the existence of the polar decomposition for densely defined closed right linear operators in quaternionic Hilbert spaces: If $T$ is a densely defined closed right linear operator in a quaternionic Hilbert space $H$, then there exists a partial isometry $U_{0}$ such that $T = U_{0}|T|$. In fact $U_{0}$ is unique if $N(U_{0}) = N(T)$. In particular, if $H$ is separable and $U$ is a partial isometry with $T = U|T|$, then we prove that $U = U_{0}$ if and only if either $N(T) = \{0\}$ or $R(T)^{\bot} = \{0\}$.Comment: 17 page

Influence of Recreational Games on Selected Fitness Components, Cognitive Skills and Psychomotor Abilities among Mild Intellectually Challenged Children

Most children have the option to participate in recreation, after school activities, weekend team sports, and summer camps. At school, they have a chance to exercise in physical education classes and in the playground at recess. However, these are limited for children with disabilities. Children with disabilities want to have friends, enjoy activities, and be included like everyone else. Like other children their interests range from swimming and sports, to visiting parks and playgrounds and attending summer camps with friends. The purpose of this study was to find out Influence of Recreational games on selected fitness components, cognitive skills and psychomotor abilities among mild intellectually challenged children from age group of 10 to 15 years both boys and girls and forty five students who were study in Coimbatore District. The subjects were divided in to three groups, each group consisting of 15 each. Experimental group I participated in unified play activities with partner who is normal for a period of 12 weeks training. Experimental group II participated in unified play activities among themselves for a period of 12 weeks training. Control group did not participate in unified play activities. The subjects were tested on selected criterion variables physical fitness variables as flexibility, leg explosive power and balance, Cognitive skills span of memory and span of attention and psychomotor ability reaction time, finger – eye coordination and hand – eye coordination before the training and after 12 weeks of training. The analysis of covariance was applied to find out the significant difference among the 10 -14 years of all groups in the selected variables. The “t” ratio was applied to find out significant improvement in the selected variables in each group

Phenotypic evaluation of indigenous Brinjal types suitable for rainfed conditions of South India (Tamil Nadu)

Research work was undertaken in brinjal (Solanum melongena L.) local types to identify suitable varieties for cultivation with high yield and quality traits under Madurai (Southern India) condition. The study reveals that highly significant differences were observed for most of the traits. Mean performance showed that EP 27 (1.93 kg) registered the highest fruit yield per plant followed by EP 3 (1.83 kg). From the nutrient point of view, the genotype Keerikai recorded highest ascorbic acid content of 13.87 mg/100 g, followed by Kallampatty. Earliness was one of the important criteria under rainfed conditions which ranged from 75.00 (Keerikai Local) to 85.00 (EP 28). Hence, these genotypes could be better utilized for further breeding programme for the improvement of fruit yield.Keywords: Mean performance, yield attributes, selection, eggplantAfrican Journal of Biotechnology Vol. 12(27), pp. 4338-4342

Gene Action and Combining Ability Analysis in Brinjal (Solanum melongena L.)

Combining ability analysis in brinjal genotypes indicated significant genotypic and environmental variations for all the 15 characters studied. Both general combining ability (GCA) and specific combining ability (SCA) variances showed significant interactions. Genotypes Palamedu Local (L5), Alagarkovil Local (L4), Melur Local (L6) and Annamalai (T1) were found to be good general combiners, and the crosses L3 x T3 (Kariapatty Local x Punjab Sadabahar), L8 x T1, (Nilakottai Local x Annamalai), L4 x T1 (Alagarkovil Local x Annamalai), L6 x T2 (Melur Local x KKM 1), L7 x T3 (Keerikai Local x Punjab Sadabahar) and L7 x T2 (Keerikai Local x KKM 1) were identified as good specific combiners for fruit yield and other related traits. These hybrid combinations can be used for commercial exploitation for fruit yield in brinjal