3,968 research outputs found

    Black-body furnace Patent

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    Development of black-body source calibration furnac

    Antipollution system to remove nitrogen dioxide gas

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    Gas phase reaction system using anhydrous ammonia removes nitrogen dioxide. System consists of ammonia injection and mixing section, reaction section /reactor/, and scrubber section. All sections are contained in system ducting

    A hot gas generator for large scale supersonic combustor testing

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    Exhaust gas of hydrazine-nitrogen tetroxide rocket for simulating combustor inlet requirements of scramjet engine

    Towards deterministic equations for Levy walks: the fractional material derivative

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    Levy walks are random processes with an underlying spatiotemporal coupling. This coupling penalizes long jumps, and therefore Levy walks give a proper stochastic description for a particle's motion with broad jump length distribution. We derive a generalized dynamical formulation for Levy walks in which the fractional equivalent of the material derivative occurs. Our approach will be useful for the dynamical formulation of Levy walks in an external force field or in phase space for which the description in terms of the continuous time random walk or its corresponding generalized master equation are less well suited

    High-response on-line gas analysis system for hydrogen-reaction combustion products

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    The results of testing an on-line quadrupole gas analyzer system are reported. Gas samples were drawn from the exhaust of a hydrogen-oxygen-nitrogen rocket which simulated the flow composition and dynamics at the combustor exit of a supersonic combustion ramjet engine. System response time of less than 50 milliseconds was demonstrated, with analytical accuracy estimated to be + or - 5 percent. For more complex chemical systems with interfering atom patterns, analysis would be more difficult. A cooled-gas pyrometer probe was evaluated as a total temperature indicator and as the primary mass flow measuring element for the total sample flow rate

    Scaled Brownian motion: a paradoxical process with a time dependent diffusivity for the description of anomalous diffusion

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    Anomalous diffusion is frequently described by scaled Brownian motion (SBM), a Gaussian process with a power-law time dependent diffusion coefficient. Its mean squared displacement is ⟨x2(t)⟩≃K(t)t\langle x^2(t)\rangle\simeq\mathscr{K}(t)t with K(t)≃tα−1\mathscr{K}(t)\simeq t^{\alpha-1} for 0<α<20<\alpha<2. SBM may provide a seemingly adequate description in the case of unbounded diffusion, for which its probability density function coincides with that of fractional Brownian motion. Here we show that free SBM is weakly non-ergodic but does not exhibit a significant amplitude scatter of the time averaged mean squared displacement. More severely, we demonstrate that under confinement, the dynamics encoded by SBM is fundamentally different from both fractional Brownian motion and continuous time random walks. SBM is highly non-stationary and cannot provide a physical description for particles in a thermalised stationary system. Our findings have direct impact on the modelling of single particle tracking experiments, in particular, under confinement inside cellular compartments or when optical tweezers tracking methods are used.Comment: 7 pages, 5 figure

    Next-to-Next-to-Leading Electroweak Logarithms for W-Pair Production at LHC

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    We derive the high energy asymptotic of one- and two-loop corrections in the next-to-next-to-leading logarithmic approximation to the differential cross section of WW-pair production at the LHC. For large invariant mass of the W-pair the (negative) one-loop terms can reach more than 40%, which are partially compensated by the (positive) two-loop terms of up to 10%.Comment: 23 pages, 9 figures, added explanations in section 3, corrected typos and figures 7, 8,

    Definition study of the Shuttle Imaging Radar-A (SIR-A) antenna on the second space shuttle mission (OFT-2)

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    A definition is derived for an antenna configuration fixed-mounted high in the payload bay on the hybrid OFT-2 pallet which is compatible with Orbiter interface requirements. Tests showed that the combination of the selected panels and the designed corporate feed meets SIR-A performance requirement of 33 db gain. The effects of Orbiter structure proximity on performance were determined by scale model tests to be negligible. The potential for improved performance during subsequent reflights includes a multiple-beam capability and dual polarization

    Facilitation of polymer looping and giant polymer diffusivity in crowded solutions of active particles

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    We study the dynamics of polymer chains in a bath of self-propelled particles (SPP) by extensive Langevin dynamics simulations in a two dimensional system. Specifically, we analyse the polymer looping properties versus the SPP activity and investigate how the presence of the active particles alters the chain conformational statistics. We find that SPPs tend to extend flexible polymer chains while they rather compactify stiffer semiflexible polymers, in agreement with previous results. Here we show that larger activities of SPPs yield a higher effective temperature of the bath and thus facilitate looping kinetics of a passive polymer chain. We explicitly compute the looping probability and looping time in a wide range of the model parameters. We also analyse the motion of a monomeric tracer particle and the polymer's centre of mass in the presence of the active particles in terms of the time averaged mean squared displacement, revealing a giant diffusivity enhancement for the polymer chain via SPP pooling. Our results are applicable to rationalising the dimensions and looping kinetics of biopolymers at constantly fluctuating and often actively driven conditions inside biological cells or suspensions of active colloidal particles or bacteria cells.Comment: 15 pages, 9 figures, IOPLaTe

    Welding, brazing, and soldering handbook

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    Handbook gives information on the selection and application of welding, brazing, and soldering techniques for joining various metals. Summary descriptions of processes, criteria for process selection, and advantages of different methods are given
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