GMRT observations of X-shaped radio sources

We present results from a study of X-shaped sources based on observations using the Giant Metrewave Radio Telescope (GMRT). These observations were motivated by our low frequency study of 3C 223.1 (Lal & Rao 2005), an X-shaped radio source, which showed that the wings (or low-surface-brightness jets) have flatter spectral indices than the active lobes (or high-surface-brightness jets), a result not easily explained by most models. We have now obtained GMRT data at 240 and 610 MHz for almost all the known X-shaped radio sources and have studied the distribution of the spectral index across the sources. While the radio morphologies of all the sources at 240 and 610 MHz show the characteristic X-shape, the spectral characteristics of the X-shaped radio sources, seem to fall into three categories, namely, sources in which (A) the wings have flatter spectral indices than the active lobes, (B) the wings and the active lobes have comparable spectral indices, and (C) the wings have steeper spectral indices than the active lobes. We discuss the implications of the new observational results on the various formation models that have been proposed for X-shaped sources.Comment: The paper contains 12 figures and 3 tables, accepted for publication in MNRAS Main Journal, please note, some figures are of lower qualit

Size scale effect in cavitation erosion

An overview and data analyses pertaining to cavitation erosion size scale effects are presented. The exponents n in the power law relationship are found to vary from 1.7 to 4.9 for venturi and rotating disk devices supporting the values reported in the literature. Suggestions for future studies were made to arrive at further true scale effects

A comprehensive analysis of cavitation and liquid impingement erosion data

Cavitation-erosion experimental data previously covering several materials tested in a rotating disk device and a magnetostriction apparatus were analyzed using new normalization and curve-fitting techniques. From this process a universal approach is derived which can include data from cavitation and liquid impingement studies for specific materials from different test devices

Universal approach to analysis of cavitation and liquid-impingement erosion data

Cavitation erosion experimental data was analyzed by using normalization and curve-fitting techniques. Data were taken from experiments on several materials tested in both a rotating disk device and a magnetostriction apparatus. Cumulative average volume loss rate and time data were normalized relative to the peak erosion rate and the time to peak erosion rate, respectively. From this process a universal approach was derived that can include data on specific materials from different test devices for liquid impingement and cavitation erosion studies

Design and breadboard evaluation of the SPS reference phase control system concept

The total breadboard system includes one pilot transmitter, one pilot receiver, nine phase distribution units, and two power transponders. With this complement of equipment, segments of a typical phase distribution system can be assembled to facilitate the evaluation of significant system parameters. The achievable accuracy of a large phase distribution system, the sensitivity of the system to parameter variations, and the limitations of commercially available components in such applications were determined

Spherical micro-glass particle impingement studies of thermoplastic materials at normal incidence

Light optical and scanning electron microscope studies were conducted to characterize the erosion resistance of polymethyl methacrylate (PMMA), polycarbonate (PC), polytetrafluoroethylene (PTFE) and ultra-high-molecular-weight-polyethylene (UHMWPE). Erosion was caused by a jet of spherical micro-glass beads at normal impact. During the initial stages of damage, the surfaces of these materials were studied using a profilometer. Material buildup above the original surface was observed on PC and PMMA. As erosion progressed, this buildup disappeared as the pit became deeper. Little or no buildup was observed on PTFE and on UHMWPE. UHMWPE and PTFE are the most resistant materials and PMMA the least. Favorable properties for high erosion resistance seem to be high values of ultimate elongation, and strain energy and a low value of the modulus of elasticity. Erosion-rate-versus-time curves of PC and PTFE exhibit incubation, acceleration and steady state periods. A continuously increasing erosion rate period was observed however for PMMA instead of a steady state period. At early stages of damage and at low impact pressure material removal mechanisms appear to be similar to those for metallic materials

Initial stages of cavitation damage and erosion on copper and brass tested in a rotating disk device

In view of the differences in flow and experimental conditions, there has been a continuing debate as to whether or not the ultrasonic method of producing cavitation damage is similar to the damage occurring in cavitating flow systems, namely, venturi and rotating disk devices. In this paper, the progress of cavitation damage during incubation periods on polycrystalline copper and brass tested in a rotating disk device is presented. The results indicate several similarities and differences in the damage mechanism encountered in a rotating disk device (which simulates field rotary devices) and a magnetostriction apparatus. The macroscopic erosion appears similar to that in the vibratory device except for nonuniform erosion and apparent plastic flow during the initial damage phase

Empirical relations for cavitation and liquid impingement erosion processes

A unified power-law relationship between average erosion rate and cumulative erosion is presented. Extensive data analyses from venturi, magnetostriction (stationary and oscillating specimens), liquid drop, and jet impact devices appear to conform to this relation. A normalization technique using cavitation and liquid impingement erosion data is also presented to facilitate prediction. Attempts are made to understand the relationship between the coefficients in the power-law relationships and the material properties

Role of Triacetin additive in the performance of single cylinder D I diesel engine with COME biodiesel

In the present work, COME-Triacetin additive blends are experimented in lieu of the neat diesel fuel. Pure coconut oil methyl ester (COME) itself as an additive has advantages in the operation of engine. Attention is bestowed upon the reduction of HC, NO, CO2, CO and smoke emissions, and the same is successfully achieved with the 10% Triacetin and 90% COME blend fuel. Vibration on the engine cylinder in three directions and on the foundation were measured and analyzed to elicit information about the nature of combustion. The pressure signatures are tallied with time waves eliminating the time lag in between exciter and the cylinder head vibration. Triacetin being an antiknock fuel, with 10% blend emanated as a best blend with its contribution to reduce cylinder vibration in vertical direction of the cylinder. The time wave resembles attenuated sine wave replete with pure harmonics indicating smoother combustion with lesser engine detonation. By analyzing the measured in-cylinder pressure data and the derived heat release rate, it is concluded that the addition of triacetin increases the ignition delay and the amount of heat release in the premixed combustion duration, but shortens both the diffusive burning duration and total combustion duration. On the emission side, the smoke and other emissions including NO are reduced without any cognizable trade off with other components of the emissions

Influence of Mo6+ on Dielectric properties of Copper Ferrites

Two series of copper ferrites are prepared using the chemical compositional formula Cu1.0-3y Fe2.0-2x Mox + yO4.0. They are calcinated at 750 C and sintered at 950C.When x =y = 0.0, the ε′ of the basic copper ferrite is probably due to electronic exchange interactions of copper and iron ions as Cu2+↔ Cu1+ and Fe3+↔ Fe2+. The observed value of dielectric constant (є′) decreases as a function of substituent concentration (x) up to x = 0.20 and for further values of ‘x’ it found to increase. In the case of ‘C’ (x = 0) series ferrites є′ decreases with substituent concentration (y) up to y = 0.04, later it found to increase. The dispersion of ac resistivity with frequency is observed indicating their strong dependence on frequency as in the case of dielectric behaviour. These results are explained with different possible mechanisms