4,351 research outputs found

    Tracking ocean heat uptake during the surface warming hiatus.

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    Ocean heat uptake is observed to penetrate deep into the Atlantic and Southern Oceans during the recent hiatus of global warming. Here we show that the deep heat penetration in these two basins is not unique to the hiatus but is characteristic of anthropogenic warming and merely reflects the depth of the mean meridional overturning circulation in the basin. We find, however, that heat redistribution in the upper 350 m between the Pacific and Indian Oceans is closely tied to the surface warming hiatus. The Indian Ocean shows an anomalous warming below 50 m during hiatus events due to an enhanced heat transport by the Indonesian throughflow in response to the intensified trade winds in the equatorial Pacific. Thus, the Pacific and Indian Oceans are the key regions to track ocean heat uptake during the surface warming hiatus

    Numerical and Experimental Investigation of Near-Field Mixing in Parallel Dual Round Jets

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    Parallel underexpanded round jets system has been widely used in engineering applications, and the flow field structures are very complex because of the jets interaction. In this paper, we studied the near-field mixing phenomenon in parallel dual underexpanded jets numerically by solving the Reynolds-Averaged Navier-Stokes Equations. The numerical results agree well with experimental data acquired by particle image velocimetry. Similar to plane jets, to some degree, two round jets are deflected towards the dual nozzle symmetry plane; the flow field can also be divided into three regions. Meanwhile, attempts have been made to predict merge point and combine point locations on certain cross profile of computational domain by correlating them with jet spacing and jet pressure ratio. The jet spacing plays an important role in jets interaction, and jet interaction decreases with the increase in jet spacing. The jets interaction in terms of merge (combine) point and pressure varies significantly while the jet spacing differs. Additionally, as pressure ratio increases, the effect of jet interaction decreases, and the merge (combine) point location moves downstream

    Fuzzy Adaptive PID Control of a New Hydraulic Erecting Mechanism

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    Conventional erecting mechanism is cumbersome and the erecting velocity is slow, so a new hydraulic erecting mechanism is introduced in this paper. But it has two problems. First is the cooperation problem between the erect cylinder and the horizontal cylinder. Second, the nonlinearities and uncertainties exist in the system make the control precision poor. So the combined simulation model is built based on the software AMESim and Simulink. And from this model, the best cooperation time is confirmed. Further, the fuzzy adaptive PID controller is introduced to improve the control performance aiming to the nonlinearities and uncertainties. The fuzzy inference rules and parameters of the controller are also presented in this paper. Experiment results show that the cooperation time which received from the simulation is correct, and the fuzzy adaptive PID controller has nice tracking performance compared to the conventional PID controller and fuzzy controller

    From Dust To Planetesimal: The Snowball Phase ?

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    The standard model of planet formation considers an initial phase in which planetesimals form from a dust disk, followed by a phase of mutual planetesimal-planetesimal collisions, leading eventually to the formation of planetary embryos. However, there is a potential transition phase (which we call the "snowball phase"), between the formation of the first planetesimals and the onset of mutual collisions amongst them, which has often been either ignored or underestimated in previous studies. In this snowball phase, isolated planetesimals move on Keplerian orbits and grow solely via the direct accretion of sub-cm sized dust entrained with the gas in the protoplanetary disk. Using a simplified model in which planetesimals are progressively produced from the dust, we consider the expected sizes to which the planetesimals can grow before mutual collisions commence and derive the dependence of this size on a number of critical parameters, including the degree of disk turbulence, the planetesimal size at birth and the rate of planetesimal creation. For systems in which turbulence is weak and the planetesimals are created at a low rate and with relatively small birth size, we show that the snowball growth phase can be very important, allowing planetesimals to grow by a factor of 10^6 in mass before mutual collisions take over. In such cases, the snowball growth phase can be the dominant mode to transfer mass from the dust to planetesimals. Moreover, such growth can take place within the typical lifetime of a protoplanetary gas disk. A noteworthy result is that ... ...(see the paper). For the specific case of close binaries such as Alpha Centauri ... ... (see the paper). From a more general perspective, these preliminary results suggest that an efficient snowball growth phase provides a large amount of "room at the bottom" for theories of planet formation.Comment: Accepted for publication in the Astrophysical Journal. 15 pages, 4 figures, 1 tabl

    Interacting Multiple Model Algorithm with the Unscented Particle Filter (UPF)

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    AbstractCombining interacting multiple model (IMM) and unscented particle filter (UPF), a new multiple model filtering algorithm is presented. Multiple models can be adapted to targets' high maneuvering. Particle filter can be used to deal with the nonlinear or non-Gaussian problems and the unscented Kalman filter (UKF) can improve the approximate accuracy. Compared with other interacting multiple model algorithms in the simulations, the results demonstrate the validity of the new filtering method

    (Formato-κO)bis­(1,10-phenanthroline-κ2 N,N′)copper(II) formate hexa­hydrate

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    In the title compound, [Cu(CHO2)(C12H8N2)2]CHO2·6H2O, the Cu atom is coordinated in a distorted trigonal-bipyramidal fashion by an O atom of the formate ligand and four N atoms of two phenanthroline ligands with Cu—O and Cu—N distances of 2.020 (3) and 1.978 (3)–2.177 (3) Å, respectively. Hydrogen bonding O—H⋯O between water molecules and between water anions as well as π–π inter­actions [centroid–centroid distances between phen rings = 3.38 (7) and 3.40 (5) Å] are responsible for the supra­molecular assembly
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