3,907 research outputs found

    Aeration Effects on Impact: Drop Test of a Flat Plate

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    Verbatim reproduction or republication of the papers or articles or part of the articles (e.g., figures or tables) by their authors, after the publication or presentation at the ISOPE meetings and journal, is permitted by the International Society of Offshore and Polar Engineers (ISOPE), provided the full credit is given to the authors, to the publisher, The International Society of Offshore and Polar Engineers (ISOPE), and to the Conference, Symposium or Journal - more specifically not to remove the copyright imprint on page 1 of the paper. The permission does not extend to copying for resale and to re-copyrighting the whole or part of the papers. Posting on your organization's website of the paper(s) you specified is allowed only where only your organization's employees including the students can view free of charge the paper authored or co-authored by your organization's employees, and www.isope.org is provided for the paper(s) in the ISOPE proceedings or journals. Regards, Prof. Jin S Chung Executive Director isope, 495 North Whisman Road, Suite 300 Mountain View, California 94043-5711, USA T 1-650-254-1871; F 1-650-254-2038; [email protected] [email protected], www.isope.org www.deepoceanmining.orgAeration effects on impact have been investigated by dropping a flat plate onto the water surface, in which the water is aerated to various degrees. An experimental study has been carried out in the newly commissioned Ocean Basin at Plymouth University’s COAST Lab. The falling block comprises a rigid impact plate connected to two driver plates and its total mass can be varied between 32 kg and 52 kg. The impact plate is 0.25m long, 0.25 m wide and 0.012 m high. The impact velocity is varied between 4 m/s and 7 m/s. Preliminary results of the impact tests are presented here. Visualised results show that there are significant differences between jet formation after impact of the plate in pure water and in aerated water. There is significant reduction of the maximum pressures from those measured in pure water to those measured in aerated water

    Methodology for tidal turbine representation in ocean circulation model

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    The present method proposes the use and adaptation of ocean circulation models as an assessment tool framework for tidal current turbine (TCT) array layout optimization. By adapting both momentum and turbulence transport equations of an existing model, the present TCT representation method is proposed to extend the actuator disc concept to 3-D large-scale ocean circulation models. Through the reproduction of experimental flume tests and grid dependency tests, this method has shown its numerical coherence as well as its ability to simulate accurately both momentum and turbulent turbine-induced perturbations in both near and far wakes in a relatively short period of computation time. Consequently the present TCT representation method is a very promising basis for the development of a TCT array layout optimization tool

    Absence of magnetic long range order in Y2_{2}CrSbO7_{7}: bond-disorder induced magnetic frustration in a ferromagnetic pyrochlore

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    The consequences of nonmagnetic-ion dilution for the pyrochlore family Y2_{2}(M1−xNxM_{1-x}N_{x})2_{2}O7_{7} (MM = magnetic ion, NN = nonmagnetic ion) have been investigated. As a first step, we experimentally examine the magnetic properties of Y2_{2}CrSbO7_{7} (xx = 0.5), in which the magnetic sites (Cr3+^{3+}) are percolative. Although the effective Cr-Cr spin exchange is ferromagnetic, as evidenced by a positive Curie-Weiss temperature, ΘCW\Theta_\mathrm{{CW}} = 20.1(6) K, our high-resolution neutron powder diffraction measurements detect no sign of magnetic long range order down to 2 K. In order to understand our observations, we performed numerical simulations to study the bond-disorder introduced by the ionic size mismatch between MM and NN. Based on these simulations, bond-disorder (xbx_{b} ≃\simeq 0.23) percolates well ahead of site-disorder (xsx_{s} ≃\simeq 0.61). This model successfully reproduces the critical region (0.2 < xx < 0.25) for the N\'eel to spin glass phase transition in Zn(Cr1−x_{1-x}Gax_{x})2_{2}O4_{4}, where the Cr/Ga-sublattice forms the same corner-sharing tetrahedral network as the M/NM/N-sublattice in Y2_{2}(M1−xNxM_{1-x}N_{x})2_{2}O7_{7}, and the rapid drop in magnetically ordered moment in the N\'eel phase [Lee etet alal, Phys. Rev. B 77, 014405 (2008)]. Our study stresses the nonnegligible role of bond-disorder on magnetic frustration, even in ferromagnets

    The effectiveness of dieldrin for control of the Argentine ant in Western Australia

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    The results of three experiments to compare insecticides for the eradication of Argentine ants are reported. The areas used for the tests were typical household allotments in Shenton Park, a suburb of Perth, Western Australia. The methods of application of sprays and evaluation of results were the same as described in a previous paper. (Forte & Greaves 1953.

    New insecticides for the control of the Argentine ant in Western Australia

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    The Argentine Ant (Iridomyrmex humilis Mayr), has been the subject of much investigation in Western Australia. Jenkins (1943), Jenkins and Forte (1946, 1951), Jenkins (1948) and Forte (1949) have reported results of extensive work on the control of this pest. The results of the investigations have shown that effective control can be obtained by the use of DDT sprays but that large scale eradication was not possible with DDT

    The Removal of Artificially Generated Polarization in SHARP Maps

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    We characterize the problem of artificial polarization for the Submillimeter High Angular Resolution Polarimeter (SHARP) through the use of simulated data and observations made at the Caltech Submillimeter Observatory (CSO). These erroneous, artificial polarization signals are introduced into the data through misalignments in the bolometer sub-arrays plus pointing drifts present during the data-taking procedure. An algorithm is outlined here to address this problem and correct for it, provided that one can measure the degree of the sub-array misalignments and telescope pointing drifts. Tests involving simulated sources of Gaussian intensity profile indicate that the level of introduced artificial polarization is highly dependent upon the angular size of the source. Despite this, the correction algorithm is effective at removing up to 60% of the artificial polarization during these tests. The analysis of Jupiter data taken in January 2006 and February 2007 indicates a mean polarization of 1.44%+/-0.04% and 0.95%+/-0.09%, respectively. The application of the correction algorithm yields mean reductions in the polarization of approximately 0.15% and 0.03% for the 2006 and 2007 data sets, respectively.Comment: 19 pages, 7 figure

    Integrated Numerical Modelling System for Extreme Wave Events at the Wave Hub Site

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    This paper examines an extreme wave event which occurred during a storm at the Wave Hub site in 2012. The extreme wave of 9.57 m height was identified from a time series of the heave data collected by an Oceanor Seawatch Mini II Buoy deployed at the site. An energy density spectrum was derived from this time series and then used to drive a physical model, which represents the extreme wave at 1:20 scale in Plymouth University’s new COAST Lab. The NewWave technique was used to define the input to the physical model. The experiment is reproduced in a numerical wave tank using the fully nonlinear CFD library OpenFOAM¼ and the wave generation toolbox waves2Foam. Results are evaluated, and issues regarding the predictions of a numerical model that is driven by the NewWave input signal are discussed. This study sets the basis for further research in coupling field data, physical modelling and numerical modelling in a more efficient and balanced way. This will lead to the new approach of composite modelling that will be implemented in future work

    Bulletin No. 274 - Influence of Rotation and Manure on the Nitrogen, Phosphorus, and Carbon of the Soil

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    All agricultural plants require carbon, hydrogen, oxygen, nitrogen, calcium, potassium, magnesium, sulfur, phosphorus, iron, and probably traces of other elements for their normal growth and fruition. The growth of farm crops is dependent upon an available supply of these elements, and the extent of growth is governed by the one present and available in least quantity in proportion to the plant\u27s needs. Of the essential elements, all plants secure two (carbon and oxygen) from the air, one (hydrogen) from the water, and the others from the soil. Most soils contain sufficient plant nutrients for normal plant production, with the exception of nitrogen, phosphorus, and potassium. These elements are used by the plants from the soil in the largest quantities and are generally the plant nutrients governing the productivity of a soil. In addition, the organic matter of the soil is of prime importance, for it is the matrix which holds the nitrogen and governs the structure and water-holding capacity of the soil. Probably most Utah soils contain sufficient potassium; consequently, the problem of Utah soil fertility resolves itself into maintaining an optimum concentration of nitrogen, phosphorus, and organic material in the soil. Therefore, this work represents a study of the influence of manure and crop rotation on the nitrogen, phosphorus, and carbon in the soil
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