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  • 1
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    Role of wind in erosion–accretion cycles on an estuarine mudflat (2016)
    Wiley
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    Publikationsdatum: 2016-11-29
    Beschreibung: Wind is an important regulator of coastal erosion and accretion processes that have significant ecological and engineering implications. Nevertheless, previous studies have mainly focused on storm−generated changes in the bed level. This paper aims to improve the understanding of wind−induced erosion–accretion cycles on intertidal flats under normal (non−stormy) weather conditions using data that relates to the wave climate, near−bed 3D flow velocity, suspended sediment concentration, and bed−level changes on a mudflat at the Yangtze Delta front. The following parameters were calculated at 10−minute intervals over 10 days: the wind wave orbital velocity (Û δ ), bed shear stress from combined current–wave action, erosion flux, deposition flux, and predicted bed−level change. The time series of measured and predicted bed−level changes both show tidal cycles and a 10−day cycle. We attribute the tidal cycles of bed−level changes to tidal dynamics, but we attribute the 10−day cycle of bed−level changes to the interaction between wind speed/direction and neap−spring cyclicity. We conclude that winds can significantly affect bed−level changes in mudflats even during non−stormy weather and under macro−mesotidal conditions and that the bed−level changes can be predicted well using current–wave–sediment combined models. This article is protected by copyright. All rights reserved.
    Print ISSN: 0148-0227
    Thema: Geologie und Paläontologie , Physik
    Publiziert von Wiley im Namen von American Geophysical Union (AGU).
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  • 2
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    Modeling long-term change of planktonic ecosystems in the northern South China Sea and the upstream Kuroshio Current (2015)
    Wiley
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    Publikationsdatum: 2015-05-15
    Beschreibung: Field studies suggested that the biogeochemical settings and community structures are substantial different between the central Northern South China Sea (NSCS) and the upstream Kuroshio Current (KC). In particular, the water column of KC is characterized by substantially lower nutrients and productivity but higher Trichodesmium abundance and nitrogen fixation compared to the NSCS. The mechanism driving the difference of the two marine ecosystems, however, remains inadequately understood. Here, a one-dimensional biogeochemical model was developed to simulate the long-term variability of lower-trophic planktonic ecosystem for two pelagic stations in the NSCS and the KC near the Luzon Strait. The physical model included the vertical mixing driven by air-sea interaction and the Ekman pumping induced by wind stress curl. The biological model was constructed by modifying a nitrogen-based NPZD model with the incorporation of phosphorus cycle and diazotroph nitrogen fixation. After validation by several field datasets, the model was used to study the impact of long-term physical forcing on ecosystem variability in the two distinct stations. Our results suggested that nutrient transport above nitracline during summer was largely controlled by vertical turbulent mixing, while Ekman pumping was important for nutrient transport below the nitracline. Our results also indicated that diazotroph community structure and N 2 fixation in the NSCS and the KC could be strongly influenced by physical processes through the impacts on vertical nutrient fluxes. The disadvantage of diazotroph in the NSCS in compared to the KC during the summer could be attributed to its high nitrate fluxes from subsurface leading to outcompete of diazotrophs by faster growing non-diazotroph phytoplankton. This article is protected by copyright. All rights reserved.
    Print ISSN: 0148-0227
    Thema: Geologie und Paläontologie , Physik
    Publiziert von Wiley im Namen von American Geophysical Union (AGU).
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  • 3
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    RRR and thermal conductivity of Ag and Ag-0.2 wt.%Mg alloy in Ag/Bi-2212 wires (2015)
    Institute of Physics (IOP)
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    Publikationsdatum: 2015-12-19
    Beschreibung: Residual resistivity ratio (RRR) and thermal conductivity of metal matrix in metal/superconductor composite wires are important parameters for designing superconducting magnets. However, the resistivity of silver in reacted Ag/Bi-2212 wires has yet to be determined over temperature range from 4.2 K to 80 K because Bi-2212 filaments have a critical transition temperature T c of ∼ 80 K, and because it is unknown whether the RRR of Ag/Bi-2212 degrades with Cu diffusing from Bi-2212 filaments into silver sheathes at elevated temperatures and to what degree it varies with heat treatment. We measured the resistivity of stand-alone Ag and AgMg (Ag-0.2 wt.% Mg) wires as well as the resistivity of Ag and Ag-0.2 wt.% Mg in Ag/Bi- 2212 round wires reacted in 1 bar oxygen at 890 °C for 1, 8, 24 and 48 hours and quickly cooled to room temperature. The heat treatment was designed to reduce the critical current I c of Bi- 2212 wires to nearly zero while allowing Cu lo...
    Print ISSN: 1757-8981
    Digitale ISSN: 1757-899X
    Thema: Maschinenbau
    Publiziert von Institute of Physics (IOP)
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  • 4
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    Effect of hydrogen storage alloy on combustion properties of ammonium perchlorate /glycidylazide polymer -based propellant (2015)
    Institute of Physics (IOP)
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    Publikationsdatum: 2015-12-11
    Beschreibung: Hydrogen storage alloys can serve as good potential fuels for propellant design, by improving the energy and combustion properties. The influence of hydrogen storage alloy (A30) on the combustion properties of ammonium perchlorate/glycidylazide polymer (AP/GAP)-based on propellant were studied. The results showed that A30 could increase the burning rate of propellants by 29.75% and 74.78%, compared with B30 and Al. The combustion model of AP/GAP-based propellant containing different fuel was built. Firstly, A30 reduced the high decomposition temperature and promote condensed phase reaction heat of AP. Secondly, A30 deduced the burning surface temperature. Thirdly, A30 might prove the explosive heat of propellant. Therefore, A30 could greatly improve combustion properties of AP/GAP-based propellant.
    Print ISSN: 1757-8981
    Digitale ISSN: 1757-899X
    Thema: Maschinenbau
    Publiziert von Institute of Physics (IOP)
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  • 5
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    The enhancing effect of mesogen-jacketed liquid crystalline polymer PBPCS on epoxy resin (2015)
    Institute of Physics (IOP)
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    Publikationsdatum: 2015-12-11
    Beschreibung: The mixtures of mesogen-jacketed liquid crystalline polymers (MJLCP) and epoxy resin (E-51) have been prepared in a certain proportion. The category of the MJLCP is poly{2, 5-bis[(4-butoxyphenyl) oxycarbonyl] styrenes} (PBPCS). Methyl tetrahydro phthalic anhydride (MeTHPA) is served as a curing agent, and N, N-dimethylbenzylamine plays the role of catalyst. Then, based on the curing process, the modified materials have been acquired by casting molding. The effect of PBPCS's improvement has been researched through the mechanical properties test, dynamic thermal mechanical test and scanning electron microscope (SEM). The results indicated that PBPCS could apparently improve the mechanical properties of resin E-51. Compared with unmodified materials, the elongation at break and the tensile strength of PBPCS have been improved remarkably through modification. Both mechanical properties of the 4wt% PBPCS/E-51/MeTHPA were enhanced by 48% and 153% separately, and the characteristics of ...
    Print ISSN: 1757-8981
    Digitale ISSN: 1757-899X
    Thema: Maschinenbau
    Publiziert von Institute of Physics (IOP)
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  • 6
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    Effects of Mackenzie River discharge and bathymetry on sea ice in the Beaufort Sea (2014)
    Wiley
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    Publikationsdatum: 2014-01-21
    Beschreibung: [1]  Mackenzie River discharge and bathymetry effects on sea ice in the Beaufort Sea are examined in 2012 when Arctic sea ice extent hit a record low. Satellite-derived sea surface temperature revealed warmer waters closer to river mouths. By 5 July 2012, Mackenzie warm waters occupied most of an open-water area about 316,000 km 2 . Surface temperature in a common open-water area increased by 6.5 °C between 14 June and 5 July 2012, before and after the river waters broke through a recurrent landfast ice barrier formed over the shallow seafloor offshore the Mackenzie Delta. In 2012, melting by warm river waters was especially effective when the strong Beaufort Gyre fragmented sea ice into unconsolidated floes. The Mackenzie and other large rivers can transport an enormous amount of heat across immense continental watersheds into the Arctic Ocean, constituting a stark contrast to the Antarctic that has no such rivers to affect sea ice.
    Print ISSN: 0094-8276
    Digitale ISSN: 1944-8007
    Thema: Geologie und Paläontologie , Physik
    Publiziert von Wiley im Namen von American Geophysical Union (AGU).
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  • 7
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    Edge Detection from High Resolution Remote Sensing Images using Two-Dimensional log Gabor Filter in Frequency Domain (2014)
    Institute of Physics (IOP)
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    Publikationsdatum: 2014-03-20
    Beschreibung: Edges are vital features to describe the structural information of images, especially high spatial resolution remote sensing images. Edge features can be used to define the boundaries between different ground objects in high spatial resolution remote sensing images. Thus edge detection is important in the remote sensing image processing. Even though many different edge detection algorithms have been proposed, it is difficult to extract the edge features from high spatial resolution remote sensing image including complex ground objects. This paper introduces a novel method to detect edges from the high spatial resolution remote sensing image based on frequency domain. Firstly, the high spatial resolution remote sensing images are Fourier transformed to obtain the magnitude spectrum image (frequency image) by FFT. Then, the frequency spectrum is analyzed by using the radius and angle sampling. Finally, two-dimensional log Gabor filter with optimal parameters is designed according ...
    Print ISSN: 1755-1307
    Digitale ISSN: 1755-1315
    Thema: Geographie , Geologie und Paläontologie , Physik
    Publiziert von Institute of Physics (IOP)
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  • 8
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    Analysis on hydraulic characteristics of Kaplan water turbine with different spiral casing and stay vane (2018)
    Institute of Physics (IOP)
    Details
    Publikationsdatum: 2018-07-31
    Beschreibung: This paper introduces a water turbine which is used to recycle rich energy for hydraulic cooling towers. That cooling tower’s head are from a few meters to more than ten meters, and mass flow is from 300t/h to 1300t/h. The water turbine has a small radius size, a long and narrow flow passage and higher velocity, so the hydraulic loss in spiral casing and stay vane is too high to decrease the hydraulic efficiency. To decrease hydraulic loss, three diversion components with different spiral casing and stay vanes are introduced. When the radial dimension of the spiral casing is same, the double-spiral casing with the same rectangle section, a spiral casing with same rectangle section and stay vane, and a common spiral casing according to the same circumferential velocity rules are designed. The simulation results show that the hydraulic efficiency of the water turbine for same rectangle section spiral casing and stay vane is highest, and that for constant circumferential velocity s...
    Print ISSN: 1755-1307
    Digitale ISSN: 1755-1315
    Thema: Geographie , Geologie und Paläontologie , Physik
    Publiziert von Institute of Physics (IOP)
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  • 9
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    Numerical simulation of the flow distribution in a trap of a propellant tank with micro gravity (2018)
    Institute of Physics (IOP)
    Details
    Publikationsdatum: 2018-07-31
    Beschreibung: A trap device is defined as a closed structure which holds and provides a specific quantity of propellant using the surface tension forces. A trap in a vane-type PMD is investigated. The influence of the cone angle of the trap and flow distributions with different conditions in space are investigated. The VOF model could be used to simulate the flow distribution in a trap with zero or small gravity condition. The optimal angle for the trap is α=45° and it has the best result of expulsion efficiency of the propellant tank. The trap can be full filled with propellant after 21 second at zero gravity condition and 37 second at north-south insurance condition. A gas bubble left in the trap at the end of the refilling process. There is no flow distribution change in the trap when the trap is full filled at reverse gravity condition and sink condition.
    Print ISSN: 1755-1307
    Digitale ISSN: 1755-1315
    Thema: Geographie , Geologie und Paläontologie , Physik
    Publiziert von Institute of Physics (IOP)
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  • 10
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    Selection and application of novel ssDNA aptamers specially recognized aquatic viral pathogens: short communication (2018)
    Institute of Physics (IOP)
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    Publikationsdatum: 2018-12-21
    Beschreibung: XXXX
    Print ISSN: 1755-1307
    Digitale ISSN: 1755-1315
    Thema: Geographie , Geologie und Paläontologie , Physik
    Publiziert von Institute of Physics (IOP)
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