Genetic variability of the bollworm, Helicoverpa armigera, occurring on different host plants

The bollworm, Helicoverpa armigera Hübner (Lepidoptera: Noctuidae) is a polyphagous pest of worldwide occurrence inflicting annual crop damage in India worth US$ 1billion. In India this insect occurs as a major pest in many economically important crops, including cotton, pigeonpea, chickpea, tomato, okra, and blackgram. Understanding the genetic variation among the H. armigera populations occurring on host plants has become essential to understand the variation in their susceptibility to different insecticides, including Bacillus thuringiensis. This preliminary study uses 10 microsatellite simple sequence repeat (SSR) markers, to provide insight into the genetic variability of H. armigera populations from six different host plants. Nine of the SSR primers indicated high variability across the different host associated populations with polymorphism ranging from 75 to 100 per cent. Using the un-weighted pair-group method analysis, H. armigera collected and reared from cotton stood out as unique in one cluster while the insects collected and reared on all other hosts grouped separately

Experimental identification of cracked rotor system parameters from the forward and backward whirl responses

In the present work, an experimental investigation of a transverse fatigue crack has been carried out. A mathematical modelling of cracked rotor system along with the measured vibration is used to find crack parameters that not only detect the fault but also quantify it. Many experimental studies on cracks considered the crack as a slit or notch, which remains open. However, such flaws do not mimic a fatigue crack behavior, in which crack front opens and closes (i.e., breathes in a single revolution of the rotor). The fatigue crack in rotors commonly depicts 2× frequency component in the response, as well as higher frequency components, such as 3×, 4× and so on. In rotors, both forward and backward whirling take place due to asymmetry in rotor, and thus the fatigue crack gives the forward and backward whirl for all such harmonics. A rotor test rig was developed with a fatigue crack in it; rotor motions in two orthogonal directions were captured from the rig at discrete rotor angular speeds using proximity probes. The directional-spectrum processing technique has been utilized to the measured displacements to get its forward and backward whirl components. Subsequently, it is executed in a mathematical model-based estimation procedure to obtain the crack forces, residual unbalances, and remaining rotor system unknown variables. Estimation of crack forces during rotation of the shaft gives its characteristics, which can be used further to develop newer crack models

Modelling and Analysis of High-Speed Angular Contact Ball Bearing

Angular contact bearings are of primal importance in accommodating rotational mechanisms with high-speed characteristics. Their applications are centric to heavy axial and radial loads sustaining thrust loads to a single direction. In high-speed applications, factors such as centrifugal force, gyroscopic moments and relative displacements in various geometric features of the bearings are to be taken into consideration. This study focuses on establishing the contact angles, contact forces and spin speed for angular contact bearing to withstand varied rotational angular velocities. The forces experience a non-linear variation with respect to the body stiffness thus necessitating the involvement of numerical methods to converge at precise solutions through each juncture. The outer raceway of the bearing is accepted to be static with respect to the inner raceway as the input shaft for any application is predominantly affixed to the inner raceway of the angular contact bearing. Geometrical variations are determined under combined load conditions to simulate the natural working of the bearing at accelerated speeds. The analyses involve results for spatial parameters which are iteratively solved for each of the rolling elements in the bearing taken into concern. The spin speeds of the rolling elements are shown to dampen and exponentially increase with respect to their angular positions. The outputs manifested through this work can be utilized to accurately predict shift of salient design attributes of an angular contact bearings through low and high-speed applications.</jats:p

Lateral and torsional vibration analysis of composite shaft

Abstract In Energy Industries reliability of rotating equipment’s plays a key role in overall plant reliability and safer operation, in fact maintaining these equipment’s in larger scale is a challenging task. The magnitude of vibration in rotating equipment’s is high when the rotor excitation force coincides with the natural frequency. This paper deals with the comparison study on existing steel shaft over laminated composite shaft’s lateral and torsional critical speed, which aims to optimize the natural frequency. The rotor system model represented here is undamped, without disc and simply supported with bearing for lateral vibration analysis and considering two discs at ends for torsional vibration analysis. The analysis report represents the comparison of both steel and laminated composite shaft, which features with Campbell diagram.</jats:p

Determination of Damping Coefficient of a Bump Foil Squeeze Film Damper

The present investigation is aiming to get better squeeze film dampers which are normally used in high speed jet engines to minimize small amplitude large force vibrations. The investigation was started with squeeze film dampers employing conventional lubricating oils. Magneto rheological fluids are then used to enhance the viscosity characteristics of the fluid under the influence of magnetic fields in order to improve the damper performances. It is observed that the dynamic characteristics of the damper with magneto rheological fluids are enhanced. Further to improve the damper performance, few modifications in the damper assembly are carried out in this research work. A good amount of reduction in the amplitude of vibrations is observed in these modified squeeze film dampers coupled with magneto rheological fluids. This research work discusses dual and triple clearance squeeze film dampers and bump foil squeeze film damper, also subjected to variation in temperature. Dynamic characteristics are found to be decreasing as the viscosity of the fluid decreases with rise in temperature of the fluid.</jats:p

Feasibility and Performance Studies of a Semi Active Journal Bearing

AbstractIn this paper, details related to preliminary efforts made towards developing a novel semi-active journal bearing have been presented. The study which is predominantly experimental in nature uses a test rig designed and fabricated for the purpose of simulating a multi-lobed journal bearing and also to study the possibility of utilising smart materials for conversion of a circular bearing profile to a multi lobed bearing profile during operation. Preliminary experimental studies have indicated that while shape memory alloy (SMA) can be used as a medium to apply necessary forces at identified locations to obtain the desired profile shapes for a multi-lobe bearing configuration facilitating the development of semi active journal bearings, ovality ratios of the bearing profile under investigation ranging from 1.5 to 2 have been realised by suitable application of direct forces in opposing directions. The performance enhancement defined in terms of stiffness and damping of the newly configured bearing equivalent to two lobed bearing over the conventional bearing has been studied. The test rig is versatile in nature, with a facility to investigate varieties of semi active journal bearings. The study indicates an increase in dynamic stiffness and damping with increase in the ovality ratio of the semi-active journal bearings

Limiting stiffness coefficients analysis of texture foil journal bearing

Abstract The purpose of this study is to explore the limiting stiffness coefficients of a foil journal bearing with the texture bump profile of top foil. The limiting stiffness coefficients are evaluated based on simplified compressible Reynolds equation for large bearing numbers with high speeds of foil journal bearing. A limiting pressure gradient solution for a texture bump of top foil bearing is analyzed. The analytical model accounts for the top foil texture bump profile and bottom foil bump compliance. Results of linearized nondimensional stiffness coefficients obtained using infinitesimal perturbation method are compared for various top foil texture bump profiles. The influence of top foil texture bump extent and height on the limiting stiffness coefficients of a foil journal bearing are investigated.</jats:p

A Novel Logic to Stator Single Phase - to - Ground Fault for Power-former

The stator single-phase to ground fault is one of the most common fault that a Generator will suffer. If such fault is neglected then there are chances of converting it into phase to phase fault. So there is need to detect and isolate the faulty part from the rest of the system as early as possible. Because of this, protection is very important otherwise there is shortage of power in our system. The proposed approach detects the ground fault by analyzing the direction, magnitude, and energy of leakage current, which is the difference of zero-sequence current fault component between the neutral and the terminal of Power-former. The aim of the study carried out was realizing 100% coverage of fault detection in internal &amp;external fault protection for the stator winding of Power former