Laminated plate analysis by hybrid stress finite element model

M.S.Stayanadham Atlur

Gap phase regeneration of tree species of differing successional status in a humid tropical forest of Kerala, India

Germination, establishment and growth of seedlings of tree species Palaquium ellipticum (primary), Actinodaphne malabarica (late secondary) and Macaranga peltata (early secondary) were studied in a humid tropical forest at Nelliampathy, in the Western Ghats of Kerala. While the primary species completed its germination within a brief period of 1.5 months, at the other extreme, early secondary species showed slow germination extending for about 5 months, the late secondary species falling in between. Although, all the species studied showed higher establishment and growth under gaps, the early secondary species were more responsive compared to the primary species. Primary species showed better establishment in undisturbed sites and natural gaps than under selection felled gaps; the reverse was true for late and early secondary species. Survival of seedlings increased with gap size, but sharply declined with gap age. Shoot/root ratio was consistently higher in the early secondary species than in the primary species

Queen success is correlated with worker-brood genetic relatedness in a primitively eusocial wasp (Ropalidia marginata)

Ropalidia marginata is a primitively eusocial polistine wasp in which, although there is only one queen at any given time, frequent queen replacements lead to a system of serial polygyny. One of the most striking features of this system is the enormous variation in the success of different queens. Measuring queen success as queen tenure, total number of offspring produced, number of offspring produced per day of tenure, and proportion of eggs laid that develop into adults, we show here that each measure of queen success is correlated with worker-brood genetic relatedness and not correlated with worker:brood ratio or the age of the queen at takeover. We interpret these results as meaning that queens are better able to obtain the cooperation of workers when worker-brood genetic relatedness is high

Ropalidia rufoplagiata: a polistine wasp society probably lacking permanent reproductive division of labour

Ropalidia rufoplagiata Cameron (Hymenoptera: Vespidae), a polistine species from penisular India, appears to be unique among all known primitively eusocial wasps. A total of 33 out of 46 identified females from an observed colony were found to oviposit on 1-17 occasions. No single predominant egg-layer could be identified during the 45-day period. Of the 17 dissected egg-layers, 12 were mated. All egg-layers showed several oviposition-related behavioural patterns including systematic, but indiscriminate, cannibalism of eggs and larvae, cleaning of empty cells, and guarding of freshly-laid eggs. There was no correlation between the egg-laying activity of the females (whether mated or not), oophagy, and their position in the dominance hierarchy. All nest-maintenance activities were performed exclusively by the egg-layers, while the non-egg-layers were mainly involved in the extranidal task offoraging. No significant morphometric differences between egg-layers and foragers could be discerned. Almost all the older individuals in the colony were egg-layers, while foragers were mainly younger animals. Such a temporal differentiation in reproductive labour suggests the absence of a permanent reproductive caste in this species

Fracture strength estimation of L3-L4 intervertebral disc using FEA

Mechanical stress and fracture analysis of the human lumbar intervertebral discs are important in assessing disorders related to lower back pain and ageing. Finite element modelling and simulation approaches assist in easier prediction of the disc behaviour under different load conditions. The causes of mechanical failure and morphological changes still remain partially speculative. The present study addresses the issue by developing a finite element model of an L3-L4 lumbar intervertebral disc subjected to different axial compressive loadings. The morphological deformations and stress concentration regions within the disc are analyzed and reported. A mathematical relation is established to estimate the breaking strength of an L3-L4 intervertebral disc, thus indicating the risk of disc failure based on the applied load

Aggressiveness of Ralstonia solanacearum isolates on Tomato

Bacterial wilt caused by Ralstonia solanacearum is the world’s most economically important destructive disease of crop plants. Fifty seven isolates of R. solanacearum causing wilt on different host plants were collected from different agro climatic zones of India of which 54 isolates were confirmed as race-1, biovar-3 and 3 isolates as race-1, biovar-3B based on morphological, physiological, biochemical and pathogenicity studies. All the isolates were authenticated as Ralstonia solanacearum by using two sets of primers (OLI1 & Y2 and Y1 & Y2). Serological identity of the isolates was done by using diagnostic kit obtained from International Potato Research Center, Lima, Peru and single chain variable fragment antibody specific to Ralstonia solanacearum. Fifty seven isolates of R. solanacearum were inoculated on tomato (Solanum Lycopersicum L) cv. Avinash-II under artificial conditions at bacterial concentration of 5x108 cfu/ml to test its aggressiveness; the results obtained are discussed in this paper

Studies on the concentration of Ra-226 and Rn-222 in drinking water samples and effective dose to the population of Davanagere district, Karnataka state, India

The concentrations of Ra-226 and Rn-222 were measured in ground water samples of Davanagere district, Karnataka state, India using emanometry technique. Activity of Ra-226 and Rn-222 in groundwater varied from 15.6 +/- 3 to 68.9 +/- 5 mBql(-1) and 37 +/- 4 to 245 +/- 8 Bql(-1) respectively. More than 53% of the water samples showed higher radon concentration compare to standard safe limit of 100 Bql(-1) prescribed by WHO. Effective dose to the public due to Rn-222 in water was found to vary from 0.15 to 1.00 mSvy(-1) with an average of 0.49 mSvy(-1)

Mode based frequency behaviour of a cracked beam

Structural analysis is mainly concerned with predicting the behaviour of a structure when subjected to any external excitation. Dynamic analysis of simple structures can be carried out using finite element analysis on various computing platforms such as MatLab. In the case of industrial applications, dynamic analysis is mainly carried out using simulations on softwares such as Ansys. The present paper compares mathematical and simulation analysis of cracked beam and the dynamic behaviour with respect to mode shape and crack position is reported

Study of Thermal Convection in Micropolar Fluids Occupying a Rectangular Box

This paper is a Fourier–series assisted numerical study of two–dimensional steady thermal convection in micropolar fluid occupying a rectangular box. The horizontal walls of the cavity are uniformly heated to establish a linear temperature in the vertical direction. The vertical walls are insulated. The critical Rayleigh number is obtained numerically as a function of coupling parameter, couple stress parameter and aspect ratio, and the same is plotted graphically. The results of slender vertical, rectangular and square box of finite aspect ratio are obtained as limiting cases of the study

The Dynamic Characteristics of a non-linear main landing gear system of an aircraft during landing

The landing gear plays a very important role during landing by absorbing the high impact energy of the aircraft. The main landing gear absorbs the bulk of the load to reduce the load experienced by both the aircraft fuselage and the nose landing gear. In this paper, a mathematical approach is used to extract the dynamic characteristics of the system. A two-degree of freedom mathematical model of the main landing gear is developed. This model is used to derive the dynamic equations of the landing gear system and to study the behaviour of main landing gear during main gear and nose gear touchdown conditions. The non-linear stiffness and damping co-efficient in an Oleo-Pneumatic shock absorber are integrated into the system to achieve a more accurate response of the system. The response of this system is established by adopting a complex modal analysis approach to account for the non-classical damping exhibited by the system. The obtained spring force, damping force and responses are reported. This work provides an alternative approach using complex modal analysis to obtain results for complex systems exhibiting non-linear characteristics