8,853 research outputs found

    Frequency and time profiles of metric wave isolated Type I solar noise storm bursts at high spectral and temporal resolution

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    Type I noise storms constitute a sizeable faction of the active-Sun radio emission component. Observations of isolated instances of such bursts, in the swept-frequency-mode at metric wavelengths, have remained sparse, with several unfilled regions in the frequency coverage. Dynamic spectra of the burst radiation, in the 30 - 130 MHz band, obtained from the recently commissioned digital High Resolution Spectrograph (HRS) at the Gauribidanur Radio Observatory, on account of the superior frequency and time resolution, have unravelled in explicit detail the temporal and spectral profiles of isolated bursts. Apart from presenting details on their fundamental emission features, the time and frequency profile symmetry, with reference to custom-specific Gaussian distributions, has been chosen as the nodal criterion to statistically explain the state of the source regions in the vicinity of magnetic reconnections, the latent excitation agent that contributes to plasma wave energetics, and the quenching phenomenon that causes damping of the burst emission.Comment: 9 pages 7 black and white / grey-scale figures (inclusive of 3 composite). MNRAS - accepte

    Nucleophilicity/Electrophilicity Excess in Analyzing Molecular Electronics

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    Intramolecular electron transfer capability of all metal aromatic and anti-aromatic aluminum cluster compounds is studied in terms of density functional theory based global and local reactivity descriptors. This study will provide important inputs towards the fabrication of the material required for molecular electronics.Comment: 21 pages, 6 figures, 13 table

    The structure of dark matter halos in hierarchical clustering theories

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    During hierarchical clustering, smaller masses generally collapse earlier than larger masses and so are denser on the average. The core of a small mass halo could be dense enough to resist disruption and survive undigested, when it is incorporated into a bigger object. We explore the possibility that a nested sequence of undigested cores in the center of the halo, which have survived the hierarchical, inhomogeneous collapse to form larger and larger objects, determines the halo structure in the inner regions. For a flat universe with P(k)∝knP(k) \propto k^n, scaling arguments then suggest that the core density profile is, ρ∝r−α\rho \propto r^{-\alpha} with α=(9+3n)/(5+n)\alpha = (9+3n)/(5+n). But whether such behaviour obtains depends on detailed dynamics. We first examine the dynamics using a fluid approach to the self-similar collapse solutions for the dark matter phase space density, including the effect of velocity dispersions. We highlight the importance of tangential velocity dispersions to obtain density profiles shallower than 1/r21/r^2 in the core regions. If tangential velocity dispersions in the core are constrained to be less than the radial dispersion, a cuspy core density profile shallower than 1/r cannot obtain, in self-similar collapse. We then briefly look at the profiles of the outer halos in low density cosmological models where the total halo mass is convergent. Finally, we analyze a suite of dark halo density and velocity dispersion profiles obtained in cosmological N-body simulations of models with n= 0, -1 and -2. We find that the core-density profiles of dark halos, show considerable scatter in their properties, but nevertheless do appear to reflect a memory of the initial power spectrum, with steeper initial spectra producing flatter core profiles. (Abridged)Comment: 31 pages, 7 figures, submitted to Ap

    Cosmological Magnetic Fields from Primordial Helical Seeds

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    Most early Universe scenarios predict negligible magnetic fields on cosmological scales if they are unprocessed during subsequent expansion of the Universe. We present a new numerical treatment of the evolution of primordial fields and apply it to weakly helical seeds as they occur in certain early Universe scenarios. We find that initial helicities not much larger than the baryon to photon number can lead to fields of about 10^{-13} Gauss with coherence scales slightly below a kilo-parsec today.Comment: 4 revtex pages, 2 postscript figures include

    A NUMERICAL SOLUTION TO DIFFERENT TYPES OF ECONOMIC LOAD DISPATCH PROBLEMS

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    This paper presents a newly proposed Novel TANAN's Algorithm (NTA) for solving different types of Economic Load Dispatch (ELD) problems. The main objective of NTA is to minimize the total fuel cost of the generating units, subjected to limits on generator power output, power loss and valve point loading effect. The NTA is a simple numerical random search approach based on a parabolic TANAN function. This paper presents an application of NTA to ELD problems for different IEEE standard test systems. The proposed method is compared with various optimization techniques and the simulation results show that the proposed algorithm outperforms previous optimization methods
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