Wear studies of Al-Si alloys

There are many properties of Aluminium-Silicon alloys such as high wear resistance, light weight, low coefficient of thermal expansion and high strength to weight ratio, that makes it suitable for many industries. In recent years, it has gained huge acceptance in automotive industries, as its use results in fuel saving, hence cost saving. These advancements make the study of properties of Al-Si alloys important. In the present study, wear behavior of Al-Si alloys were studied. Aluminium containing 10 weight % of Silicon was synthesized using casting method. The microstructure showed the presence of Proeutectic silicon. Wear behaviour was studied by using computerized pin on disc wear testing machine. The abrasion of the alloy increased as sliding distance and time increased. The crack morphology of the worn surfaces were analysed using stereo microscope

A Triple-band Suspended Microstrip Antenna with Symmetrical USlots for WLAN/WiMax Applications

In this study, a triple-band suspended microstrip antenna with symmetrical U-slots is proposed for modern wireless communication systems. The antenna is specifically designed to acquire application in WLAN and WiMAX communication. Symmetrical U-slots in the radiator patch increase the number of resonances and improve the gain response. An appropriate air height was maintained between the ground plane and the radiator patch layer for improving bandwidth operation. The impedance characteristics of the antenna are enhanced using probe feeding techniques. The proposed compact antenna is designed on a single dielectric substrate of (30×25×1.56) mm3 . Parametric analysis of the proposed structure has been realized using IE3D software. This prototype exhibits maximum impedance bandwidth of 750 MHz and gain response of 7.28 dBi. The performance of the structure at three resonating bands i.e., at 3.3 GHz, 3.78 GHz and 5.3 GHz facilitate it to be applicable for WLAN/WiMAX systems

Development and Ergonomic Evaluation of Manually Operated Weeder for Dry Land Crops

A manually operated weeder for dry land crops was developed and evaluated to find its performance. It was compared with other available weeders namely wheel finger weeder, wheel hoe and conventional weeding by using trench hoe for groundnut crop at four levels of soil moisture content of 13.52, 11.63, 9.52 and 8.04 per cent (db). It was found that the heart rate, oxygen consumption rate and energy consumption rate increases with decrease in soil moisture content for all the treatments. The highest performance index of 3689.74 was obtained with developed weeder at 11.63 per cent moisture content. Lowest plant damage (2.46 to 7.96%) and lower energy consumption rate (8.34 to 40.05 kJ/min) with highest performance index (678.66 to 3689.74) of developed weeder at different soil moisture content proved its superiority over other weeders. Soil moisture of 11.63 per cent was found to be optimum for weeding in groundnut crop and the cost of operation of developed weeder at this soil moisture content was found to be Rupees 244.00 as against Rupees 2450.00 per hectare in conventional method of weeding by using trench hoe

Existence of non-exotic traversable wormholes in squared trace extended gravity theory

An extended gravity theory is used to explore the possibility of non-exotic matter traversable wormholes. In the extended gravity theory, additional terms linear and quadratic in the trace of the energy momentum tensor are considered in the Einstein-Hilbert action. Obviously, such an addition leads to violation of the energy-momentum tensor. The model parameters are constrained from the structure of the field equations. Non-exotic matter wormholes tend to satisfy the null energy conditions. We use two different traversable wormhole geometries namely an exponential and a power law shape functions to model the wormholes. From a detailed analysis of the energy conditions, it is found that, the existence of non-exotic matter traversable wormholes is not obvious in the model considered and its possibility may depend on the choice of the wormhole geometry. Also, we found that, non-exotic wormholes are possible within the given squared trace extended gravity theory for a narrow range of the chosen equation of state parameter.Comment: 12 pages, 8 figure

On Spatial Consensus Formation: Is the Sznajd Model Different from a Voter Model?

In this paper, we investigate the so-called ``Sznajd Model'' (SM) in one dimension, which is a simple cellular automata approach to consensus formation among two opposite opinions (described by spin up or down). To elucidate the SM dynamics, we first provide results of computer simulations for the spatio-temporal evolution of the opinion distribution $L(t)$, the evolution of magnetization $m(t)$, the distribution of decision times $P(\tau)$ and relaxation times $P(\mu)$. In the main part of the paper, it is shown that the SM can be completely reformulated in terms of a linear VM, where the transition rates towards a given opinion are directly proportional to frequency of the respective opinion of the second-nearest neighbors (no matter what the nearest neighbors are). So, the SM dynamics can be reduced to one rule, ``Just follow your second-nearest neighbor''. The equivalence is demonstrated by extensive computer simulations that show the same behavior between SM and VM in terms of $L(t)$, $m(t)$, $P(\tau)$, $P(\mu)$, and the final attractor statistics. The reformulation of the SM in terms of a VM involves a new parameter $\sigma$, to bias between anti- and ferromagnetic decisions in the case of frustration. We show that $\sigma$ plays a crucial role in explaining the phase transition observed in SM. We further explore the role of synchronous versus asynchronous update rules on the intermediate dynamics and the final attractors. Compared to the original SM, we find three additional attractors, two of them related to an asymmetric coexistence between the opposite opinions.Comment: 22 pages, 20 figures. For related publications see http://www.ais.fraunhofer.de/~fran