Internal avalanches in models of granular media

We study the phenomenon of internal avalanching within the context of recently introduced lattice models of granular media. The avalanche is produced by pulling out a grain at the base of the packing and studying how many grains have to rearrange before the packing is once more stable. We find that the avalanches are long-ranged, decaying as a power-law. We study the distriution of avalanches as a function of the density of the packing and find that the avalanche distribution is a very sensitive structural probe of the system.Comment: 12 pages including 9 eps figures, LaTeX. To appear in Fractal

A case for adaptive sub-carrier level power allocation in OFDMA networks

In today's OFDMA networks, the transmission power is typically fixed and the same for all the sub-carriers that compose a channel. The sub-carriers though, experience different degrees of fading and thus, the received power is different for different sub-carriers; while some frequencies experience deep fades, others are relatively unaffected. In this paper, we make a case of redistributing the power across the sub-carriers (subject to a fixed power budget constraint) to better cope with this frequency selectivity. Specifically, we design a joint power and rate adaptation scheme (called JPRA for short) wherein power redistribution is combined with sub-carrier level rate adaptation to yield significant throughput benefits. We further consider two variants of JPRA: (a) JPRA-CR where, the power is redistributed across sub-carriers so as to support a maximum common rate (CR) across sub-carriers and (b) JPRA-MT where, the goal is to redistribute power such that the transmission time of a packet is minimized. While the first variant decreases transceiver complexity and is simpler, the second is geared towards achieving the maximum throughput possible. We implement both variants of JPRA on our WARP radio testbed. Our extensive experiments demonstrate that our scheme provides a 35% improvement in total network throughput in testbed experiments compared to FARA, a scheme where only sub-carrier level rate adaptation is used. We also perform simulations to demonstrate the efficacy of JPRA in larger scale networks. © 2012 ACM

Auralization of Amplitude Modulated Helicopter Flyover Noise

Rotorcraft noise is an active field of study as the sound produced by these vehicles is often found to be annoying. A means to auralize rotorcraft flyover noise is sought to help understand the factors leading to annoyance. Previous work by the authors auralized a complete flyover event in which the source noise synthesis traversed a range of emission angles. The source noise definition process for the synthesis used helicopter flyover recordings. Although this process yielded both periodic and aperiodic (modulation) components at a set of discrete emission angles, only the periodic components were used in the previous work to synthesize the sound of the flyover event. In the current work, aperiodic amplitude modulation is incorporated into the source noise synthesis to improve its fidelity toward assessing rotorcraft noise annoyance. The method is demonstrated using ground recordings from a flight test of the AS350 helicopter for the source noise definition

Serum protein profile in patients with pulmonary tuberculosis

A detailed study of the alterations in the serum protein fractions following commencement of effective anti-tuberculosis treatment was undertaken in 511 patients with pulmonary tuberculosis. The concentration of serum albumin was 20-30 per cent higher (P<0.001) and that of a1, a2 and g -globulins significantly lower at the end of treatment than on admission (P <0.01), the magnitude of decrease being 7-17 per cent for g -globulin, 19-30 per cent for a1- globulin and 35-38 per cent for a2- globulin. In all, 481 patients had a favourable response to treatment, 46 of whom had a bacteriological relapse within 18 months of stopping treatment. The likelihood of a relapse was found to be greater with higher a2 -globulin concentrations at the end of treatment, the proportions of patients who relapsed being 3, 9, 13 and 15 per cent with a2 -globulin concentrations of < 0.40, 0.40-0.59, 0.60-0.79 and > 0.80 g/dl (P=0.02)

Self-Structuring of Granular Media under Internal Avalanches

We study the phenomenon of internal avalanching within the context of recently proposed ``Tetris'' lattice models for granular media. We define a recycling dynamics under which the system reaches a steady state which is self-structured, i.e. it shows a complex interplay between textured internal structures and critical avalanche behavior. Furthermore we develop a general mean-field theory for this class of systems and discuss possible scenarios for the breakdown of universality.Comment: 4 pages RevTex, 3 eps figures, revised version to appear in Phys. Rev. Let

Coarsening and Slow-Dynamics in Granular Compaction

We address the problem of the microscopic reorganization of a granular medium under a compaction process in the framework of Tetris-like models. We point out the existence of regions of spatial organization which we call domains, and study their time evolution. It turns out that after an initial transient, most of the activity of the system is concentrated on the boundaries between domains. One can then describe the compaction phenomenon as a coarsening process for the domains, and a progressive reduction of domain boundaries. We discuss the link between the coarsening process and the slow dynamics in the framework of a model of active walkers on active substrates.Comment: Revtex 4 pages, 4 figures, in press in PRL. More info http://axtnt3.phys.uniroma1.it/Tetri

Seaweed culture in India-an appraisal

In recent years there has been a steady increase in the demand for naturally occuring seaweeds as a result of many seaweed based industries coming up. In order to meet the raw material requirement of these industries attempts have been made in this country to develop suitable seaweed farming techniques by some Institutes notably the CMFRI at its Mandepam. Regional Centre and CSMCRI at its field centre, Mandapam. Experimental culture of economically important seaweeds such as Gracllaria edulis, Gelidiella acerosa and other species was undertaken since 1972 at Mandapam- in these experiments production rates ranging from 3 to 8 times the initial wet weight were obtained. The techniques of seaweed culture, the favourable seasons optimum duration of culture period and the influence of environmental parameters are discussed in this account with notes on economics of seaweed culture. General information on the seaweed resources slong our coasts, their potential for exploitation and culture are also highlighted

Prediction of Rotor Position at Standstill and Flying Shaft Conditions in Switched Reluctance Machines

Development of a reliable, smooth, and precise position sensor less startup routine is an integral part of the Switched Reluctance Machine (SRM) control. the proposed sensor less startup method presented in this paper represents high grade performance and does not require additional hardware or memory. Further, the proposed sensor less technique is extended to flying shaft conditions. These capabilities are highly demanded by automotive applications such as starter/alternator and electric power steering systems. an assessment of the impact of motor parameters and diagnostic signal measurement on the quality of the sensor less startup method is also included. This will help practicing engineers to make judicious selections for implementation of the proposed technique. Experimental and theoretical results are included to validate our claims