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  • Articles  (1,365)
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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 1933-1938 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: How to describe vorticity creation from a moving wall is a long standing problem. This paper discusses relevant issues at the fundamental level. First, it is shown that the concept of "vorticity flux due to wall acceleration'' can be best understood by following fluid particles on the wall rather than observing the flow at fixed spatial points. This is of crucial importance when the time-averaged flux is to be considered. The averaged flux has to be estimated in a wall-fixed frame of reference (in which there is no flux due to wall acceleration at all); or, if an inertial frame of reference is used, the generalized Lagrangian mean (GLM) also gives the same result. Then, for some simple but typical configurations, the time-averaged vorticity flux from a harmonically oscillating wall with finite amplitude is analyzed, without appealing to small perturbation. The main conclusion is that the wall oscillation will produce an additional mean vorticity flux (a fully nonlinear streaming effect), which is partially responsible for the mechanism of vortex flow control by waves. The results provide qualitative explanation for some experimentally and/or computationally observed phenomena.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2019-11-04
    Description: Hourly values of the critical frequency of the ionospheric F region, foF2, obtained at Chongqing ionospheric observatory (geographic 29.50N, 106.40E), China, during the interval of 1977 to 1997 (solar cycle 21 and 22) have been used to investigate the dependence of the monthly median foF2 on solar activity and geomagnetic activity, and to construct single-station model (SSM) using Fourier expansion. The results of the present analysis show that there is a significant nonlinear relationship between monthly median foF2 and sunspot number R especially at daytime in each month and nighttime in summer. Furthermore, introducing geomagnetic index Ap further improves the description of variation of monthly median foF2, and the standard deviations decrease also dependently on time and month. Thus the complex influence of solar activity and geomagnetic activity may be approximately expressed by a general multiple nonlinear function at Chongqing station, China. The basic aim of this paper is to show that considering the nonlinear influence both of solar activity and geomagnetic activity improves the monthly median model. The SSM is in good agreement with observations, with standard deviation 0.65MHz, while IRI model has a lower accuracy with standard deviation 0.96MHz.
    Description: JCR Journal
    Description: open
    Keywords: solar cycle variation ; single station model ; geomagnetic index ; monthly median foF2 ; 04. Solid Earth::04.05. Geomagnetism::04.05.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
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    People’s Republic of China. Ministry of Agriculture. Bureau of Fisheries
    In:  http://aquaticcommons.org/id/eprint/16635 | 424 | 2015-05-08 12:30:42 | 16635 | COP/BMP Aquaculture
    Publication Date: 2021-07-07
    Description: Weimin, ZOU, lexian YANG, lan JIANG, Shuqin WU, Qi YI, Jianli WU
    Keywords: Fisheries ; Multiple species ; Criteria ; Asia
    Repository Name: AquaDocs
    Type: monograph
    Format: application/pdf
    Format: application/pdf
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  • 4
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    Unknown
    In:  http://aquaticcommons.org/id/eprint/16653 | 424 | 2015-05-08 13:57:30 | 16653
    Publication Date: 2021-07-07
    Keywords: Aquaculture ; Multiple species ; Guidelines ; Asia
    Repository Name: AquaDocs
    Type: monograph
    Format: application/pdf
    Format: application/pdf
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  • 5
    Publication Date: 2024-04-19
    Description: The carbon balance of peatlands is predicted to shift from a sink to a source this century. However, peatland ecosystems are still omitted from the main Earth system models that are used for future climate change projections, and they are not considered in integrated assessment models that are used in impact and mitigation studies. By using evidence synthesized from the literature and an expert elicitation, we define and quantify the leading drivers of change that have impacted peatland carbon stocks during the Holocene and predict their effect during this century and in the far future. We also identify uncertainties and knowledge gaps in the scientific community and provide insight towards better integration of peatlands into modelling frameworks. Given the importance of the contribution by peatlands to the global carbon cycle, this study shows that peatland science is a critical research area and that we still have a long way to go to fully understand the peatland–carbon–climate nexus.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5751-5753 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Partially grooved, long, rectangular grooves on the garnet surface were used to stabilize minor loop stripes in a vertical Bloch line memory. These stripes reside beneath the stripe confinement groove. The test chip contained 10 or 20 minor loop grooves, 10 read/write (r/w) gate grooves, and a major line groove. The film thickness was 4.76 μm, and the groove was 0.5 μm deep. Each minor loop groove was 500 μm long, four widths were tried: 3.5, 4, 4.5, and 5 μm. Two groove periods were tried: 10 and 20 μm. For stripe initialization, a bubble was nucleated in every minor loop groove by a single current pulse at a 90 Oe bias field. As the bias field was decreased slowly, bubbles began to stripe out at 80 Oe. At 75 Oe, all 10 stripes were stretched to the full groove length. These stripes were stable at bias fields between 70 and 80 Oe. Stripes decreased in length at higher fields, and escaped from the confinement groove at low fields. When stripes escaped from the groove, it always occured from the end not facing a r/w gate groove. These bias field values and the stripe-escape asymmetry are confirmed by computer simulation.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5754-5756 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The operation of a major line in a vertical Bloch line memory using a partial garnet grooving architecture was studied experimentally and numerically. The major line was fabricated on a 5-μm bubble garnet using three conductor layers and a 10% garnet grooving. The major line contains a bubble generator, a bubble propagation track, a bubble expander for bubble detection, and a bubble annihilator. The minimum current for bubble generation was 350 mA, at 50 ns pulse width. The bubble propagation track was a typical dual conductor design with a 5-μm-wide conductor and a 20-μm circuit period. The minimum drive current was 5 and 10 mA at an operating frequency of 250 and 500 kHz, respectively. The bias field margin was from 84 to 100 Oe. The bubble expander was a modification of the propagation track. The meandering conductor and the groove width were gradually increased to stretch the bubble into a stripe. The bias field margin was from 82 to 84 Oe. The numerical model includes the effect of the garnet grooving, and the simulation results agree with the experimental data.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 1122-1123 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the enhancement of peak-to-valley current ratios (PVCRs) of double-barrier resonant tunneling structures (DBRTSs) based on the AlGaAs/GaAs material system. The PVCRs as high as 25.4 and 18 have been obtained at 77 K for superlattice and alloy barrier structures with 0.2-μm undoped electrodes, respectively. These are the largest PVCRs to date for AlGaAs/GaAs DBRTSs. The large band bending across the undoped electrodes causes size quantization of the accumulation layer, resulting in better resonant tunneling characteristics.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 4382-4385 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We propose and demonstrate a novel operation in the vertical integration of double-barrier resonant tunneling structures (DBRTS's) in which the negative differential resistance (NDR) region can be repeated. When two DBRTS's are combined in series, one of which has a higher peak current, a lower valley current, and a larger operation range of voltage in the NDR region than those of the other, the current-voltage (I-V) characteristic shows three current peaks instead of the conventional two. This phenomenon is based on the fundamental requirement of current continuity in serially combined devices. This operation provides a method to obtain a large number of current peaks by using less DBRTS's.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 4590-4597 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Quantum waveguide structures with double-bend discontinuities were fabricated in modulation-doped AlGaAs/GaAs heterojunctions using a split-gate technique. The low field ac-conductance measurements at 50 mK show resonant peaks in the lowest quantized conductance plateau. The number of peaks increases with the effective cavity length of the double bend. This observation may be explained in terms of the allowed standing waves in the bend cavity, which is consistent with the theoretical predictions of a generalized mode-matching theory. Beyond the simple waveguide behavior, we find that the measured peak conductivity decreases as the channel length increases, which is believed to be associated with elastic scattering due to channel inhomogeneities. Magnetic field studies show that the resonance features are suppressed as the cyclotron radius approaches the one-dimensional channel width.
    Type of Medium: Electronic Resource
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