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

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

Growth and yield of Vigna radiata L.) under Terminalia arjuna and Mitragyna parvifolia based agrisilvicultural system

The present investigation was carried out in an agrisilvicultural system with treatments involving silvicultural component of 20 years old Terminalia arjuna Bedd. (Arjun) and Mitragyna parvifolia Korth (Kalam) intercropped with agricultural component of four varieties of green gram (Vigna radiata L.) viz. Pusa Vishal, GM-3, GM-4 and K-851. All the varieties of green gram were compared for growth and yield parameters like plant height (cm), number of leaves, number of branches per plant, total grain yield per plant as well as per plot at harvestablestage under Arjuna and Kalam trees. All the varieties of green gram performed superior in terms of number of leaves, numbers of branches, grain yield (per plant and per plot basis) under open condition as compared to crops under Arjuna and Kalam. However, only the plant height was found to be highest under Arjun, followed by Kalam trees. Among all the varieties tested, K-851 variety showed superiority for number of leaves (12.31) and number of branches per plant (3.96) and grain yield (2.66 gm per plant and 0.80 kg per plot) as compared to other varieties (at P=0.05). Therefore, this variety is suggested to grow in south Gujarat condition. Further, comparatively lower yield of crop under tree cover could be due to shade effect, which can be managed by regular pruning of tree branches

Developing procedures for assessment of ecological status of Indian River basins in the context of environmental water requirements

River basins / Ecology / Indicators / Environmental flows / Environmental management / Habitats / Biota / Fish / Ecosystems / India / Krishna River Basin / Chauvery River Basin / Narmada River Basin / Periyar River Basin / Ganga River Basin

Fragmentation of a Circular Disc by Impact on a Frictionless Plate

The break-up of a two-dimensional circular disc by normal and oblique impact on a hard frictionless plate is investigated by molecular dynamics simulations. The disc is composed of numerous unbreakable randomly shaped convex polygons connected together by simple elastic beams that break when bent or stretched beyond a certain limit. It is found that for both normal and oblique impacts the crack patterns are the same and depend solely on the normal component of the impact velocity. Analysing the pattern of breakage, amount of damage, fragment masses and velocities, we show the existence of a critical velocity which separates two regimes of the impact process: below the critical point only a damage cone is formed at the impact site (damage), cleaving of the particle occurs at the critical point, while above the critical velocity the disc breaks into several pieces (fragmentation). In the limit of very high impact velocities the disc suffers complete disintegration (shattering) into many small fragments. In agreement with experimental results, fragment masses are found to follow the Gates-Gaudin-Schuhmann distribution (power law) with an exponent independent of the velocity and angle of impact. The velocity distribution of fragments exhibit an interesting anomalous scaling behavior when changing the impact velocity and the size of the disc.Comment: submitted to J. Phys: Condensed Matter special issue on Granular Medi

Measurement of the damping of nuclear shell effect in the doubly magic 208^{208}Pb region

The damping of the nuclear shell effect with excitation energy has been measured through an analysis of the neutron spectra following the triton transfer in the $^7$Li induced reaction on $^{205}$Tl. The measured neutron spectra demonstrate the expected large shell correction energy for the nuclei in the vicinity of doubly magic $^{208}$Pb and a small value for $^{184}$W. A quantitative extraction of the allowed values of the damping parameter $\gamma$, along with those for the asymptotic nuclear level density parameter $\tilde{a}$, has been made for the first time.Comment: 5 pages, 5 figure