2,568 research outputs found

    Cold HI in faint dwarf galaxies

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    We present the results of a study of the amount and distribution of cold atomic gas, as well its correlation with recent star formation in a sample of extremely faint dwarf irregular galaxies. Our sample is drawn from the Faint Irregular Galaxy GMRT Survey (FIGGS) and its extension, FIGGS2. We use two different methods to identify cold atomic gas. In the first method, line-of-sight HI spectra were decomposed into multiple Gaussian components and narrow Gaussian components were identified as cold HI. In the second method, the brightness temperature (T_B) is used as a tracer of cold HI. We find that the amount of cold gas identified using the T_B method is significantly larger than the amount of gas identified using Gaussian decomposition. We also find that a large fraction of the cold gas identified using the T_B method is spatially coincident with regions of recent star formation, although the converse is not true. That is only a small fraction of the regions with recent star formation are also covered by cold gas. For regions where the star formation and the cold gas overlap, we study the relationship between the star formation rate density and the cold \HI column density. We find that the star formation rate density has a power law dependence on the HI column density, but that the slope of this power law is significantly flatter than that of the canonical Kennicutt-Schmidt relation.Comment: Accepted for publication in MNRA

    Leptogenesis bound on neutrino masses in left-right symmetric models with spontaneous D-parity violation

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    We study the baryogenesis via leptogenesis in a class of left-right symmetric models, in which DD-parity is broken spontaneously. We first discuss the consequence of the spontaneous DD-parity breaking on the neutrino masses. Than we study the lepton asymmetry in various cases, from the decay of right handed neutrino as well as the triplet Higgs, depending on their relative masses they acquire from the symmetry breaking pattern. The leptogenesis bound on their masses are discussed by taking into account the low energy neutrino oscillation data. It is shown that a TeV scale leptogenesis is viable if there are additional sources of CP violation like domain wall originating from the spontaneous DD-parity violation.Comment: 32 pages (revtex), 12 eps figures, clarifications are added in section VII, A new section VIII is added, useful references are added. Journal version, To appear in Phys. Rev.

    Neural Modeling and Control of Diesel Engine with Pollution Constraints

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    The paper describes a neural approach for modelling and control of a turbocharged Diesel engine. A neural model, whose structure is mainly based on some physical equations describing the engine behaviour, is built for the rotation speed and the exhaust gas opacity. The model is composed of three interconnected neural submodels, each of them constituting a nonlinear multi-input single-output error model. The structural identification and the parameter estimation from data gathered on a real engine are described. The neural direct model is then used to determine a neural controller of the engine, in a specialized training scheme minimising a multivariable criterion. Simulations show the effect of the pollution constraint weighting on a trajectory tracking of the engine speed. Neural networks, which are flexible and parsimonious nonlinear black-box models, with universal approximation capabilities, can accurately describe or control complex nonlinear systems, with little a priori theoretical knowledge. The presented work extends optimal neuro-control to the multivariable case and shows the flexibility of neural optimisers. Considering the preliminary results, it appears that neural networks can be used as embedded models for engine control, to satisfy the more and more restricting pollutant emission legislation. Particularly, they are able to model nonlinear dynamics and outperform during transients the control schemes based on static mappings.Comment: 15 page

    LOW ALTITUDE AIRSHIPS FOR SEAMLESS MOBILE COMMUNICATION IN AIR TRAVEL

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    The Aviation Administration policy prohibits the use of mobile phones in Aircraft during transition for the reason it may harm their communication system due to Electromagnetic interference. In case the user wants to access cellular network at higher altitudes, base station access is a problem. Large number of channels are allocated to a single user moving at high speed by various Base Stations in the vicinity to service the request requiring more resources. Low Altitude Platforms (LAPs) are provided in the form of Base stations in the Airships with antennas projected upwards which has direct link with the Ground Station. LAPs using LongEndurance Multi-Intelligence Vehicle (LEMVs) equipped with an engine for mobility and stable positioning against rough winds are utilized. This paper proposes a system that allows the passengers to use their mobiles in Aircraft using LAPs as an intermediate system between Aircraft and Ground station. As the Aircraft is dynamic, it has to change its link frequently with the Airships, MANETs using AODV protocol is established in the prototype using NS2 to provide the service and the results are encouraging

    Effect of different modes of pollination on yield parameters of summer squash (Cucurbita pepo L.) in India

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    Effect of different modes of pollination, viz., without insect pollination, hand-pollination, open-pollination and open-pollination + hand-pollination on yield parameters of 4 summer squash (Cucurbita pepo L.) hybrids viz., Parikrama, Chandra, Chamatkar and Gold Queen was studied at Research Farm of the Department of Entomology, CCS Haryana Agricultural University, Hisar during 2014. Irrespective of different hybrids, the treatment openpollination + hand-pollination and open-pollination produced the maximum number of fruits per plant (73.50 and 71.25%, respectively) followed by hand-pollination (59.08%) and no fruits were observed (0% fruit set) under without insect pollination treatment. Average fruit weight, fruit polar diameter and equatorial diameter were maximum (135.30 g, 3.74 cm and 3.47 cm, respectively) under open-pollination + hand-pollination, while these were minimum (94.81 cm, 2.14cm and 2.48 cm, respectively) under hand-pollination treatment. These results indicate that honey bees as well as wild pollinators are utmost essential for pollination of summer squash flowers and thus increasing fruit size and yield. Therefore pollinators conservation practices should be followed in summer squash growing areas for getting higher yield and returns

    Inflation in minimal left-right symmetric model with spontaneous D-parity breaking

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    We present a simplest inflationary scenario in the minimal left-right symmetric model with spontaneous D-parity breaking, which is a well motivated particle physics model for neutrino masses. This leads us to connect the observed anisotropies in the cosmic microwave background to the sub-eV neutrino masses. The baryon asymmetry via the leptogenesis route is also discussed briefly.Comment: (v1) 4 pages, 1 figure; (v2) typos corrected; (v3) title and abstract changed, numerical estimates given, minor changes; (v4) 5 pages, relations between the neutrino masses and the CMB fluctuations become more explicit, miscellaneous changes, to appear in Physical Review

    Dynamic Adaptive Control of Mobile Robot UsingRBF Networks

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    In this paper, an adaptive neuro-control systemwith two levels is proposed for the motion control of anonholonomic mobile robot. In the first level, a PD controller is designed to generate linear and angular velocities, necessary to tracka reference trajectory. In the second level, a neural network converts the desired velocities, provided by the first level, intoa torque control. The advantage of the control approach is that, no knowledge about the dynamic model is required, and no synaptic weight changing is needed in presence of robot’s parameter’s variation (mass or inertia).By introducing appropriate Lyapunovfunctions asymptotic stability of state variables and stability of system is guaranteed. The tracking performance of neural controller under disturbances is compared with PD controller. Sinusoidal trajectory and lamniscate trajectories are considered for this comparison

    Z(2)-Singlino Dark Matter in a Portal-Like Extension of the Minimal Supersymmetric Standard Model.

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    We propose a Z2-stabilized singlino () as a dark matter candidate in extended and R-parity violating versions of the supersymmetric standard model. interacts with visible matter via a heavy messenger field S, which results in a supersymmetric version of the Higgs portal interaction. The relic abundance of can account for cold dark matter if the messenger mass satisfies GeV. Our model can be implemented in many realistic supersymmetric models such as the next-to-minimal supersymmetric (SUSY) standard model and nearly minimal SUSY standard model

    Decentralized multi-tasks distribution in heterogeneous robot teams by means of ant colony optimization and learning automata

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    This paper focuses on the general problem of coordinating multiple robots. More specifically, it addresses the self-election of heterogeneous specialized tasks by autonomous robots. In this paper we focus on a specifically distributed or decentralized approach as we are particularly interested on decentralized solution where the robots themselves autonomously and in an individual manner, are responsible of selecting a particular task so that all the existing tasks are optimally distributed and executed. In this regard, we have established an experimental scenario to solve the corresponding multi-tasks distribution problem and we propose a solution using two different approaches by applying Ant Colony Optimization-based deterministic algorithms as well as Learning Automata-based probabilistic algorithms. We have evaluated the robustness of the algorithm, perturbing the number of pending loads to simulate the robot’s error in estimating the real number of pending tasks and also the dynamic generation of loads through time. The paper ends with a critical discussion of experimental results
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