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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Acta mechanica solida Sinica 4 (1991), S. 101-116 
    ISSN: 0894-9166
    Keywords: fracture ; damage mechanics ; stability of dam abutment ; arch dam ; jointed rock mass ; damage tensors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Based on continuum damage mechanics, for jointed rock masses, a fracture damage model is presented in this paper. First, the damage tensors are defined through the elastic-flexibility of intact rock and the equivalent elastic-damage flexibility for rock mass. Then, by the self-consistent principle of solid mechanics, the equivalent elastic-damage flexibility tensors involving the interaction between multicracks are deduced. The damage evolution law is proposed involving the mechanism of crack propagation process: frictional sliding, crack kinking, growing of branched tension cracks, interlinking of the microcracks near branched crack tips leading to the breakthrough of macro-cracks and finally the failure of rock mass. Thus the evolution of damage variables reasonably unified with the process of crack propagation is given. Finally, a plastic-brittle damage constitutive relation including brittle coupled strain rate, developed and applied to the stability analysis of complicated rock foundation of a dam in China, is described in this paper.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2016-07-26
    Description: By means of theory, a simplified cartoon illustrating wave forcing of the stratospheric quasi-biennial oscillation (QBO), and general circulation modeling of the QBO, it is argued that the period of the QBO is mainly controlled by the magnitude of the gravity wave (GW) vertical fluxes of horizontal momentum (GWMF) forcing the QBO, while the QBO amplitude is mainly determined by the phase speeds of the GWs that make up this momentum flux. It is furthermore argued that it is the zonally averaged GWMF that principally determines the QBO period irrespective of the longitudinal distribution of this GW momentum flux. These concepts are used to develop a hypothesis for the cause of a previously reported El Niño/Southern Oscillation (ENSO) modulation of QBO periods and amplitudes. Some observational evidence is reported for the ENSO modulation of QBO amplitudes to have been different before the 1980s than after about 1990. A hypothesis is also given to explain this in terms of the different ENSO modulation of tropical deep convection that took place before the 1980s from that which occurred after about 1990. The observational evidence, while consistent with our hypotheses, does not prove that our hypotheses are correct given the small number of El Niños and La Niñas that occurred in the early and later periods. Further research is needed to support or refute our hypotheses.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 3
    Publication Date: 2014-08-13
    Description: Three-year (2010–2013) observations of thermospheric winds (at ~250 km) by Fabry-Perot Interferometers (FPIs) at Xinglong (XL, 40.2°N, 117.4°E) and Millstone Hill (MH, 42.6°N, 71.5°W) are used to study the climatology of atmospheric Planetary Wave Type Oscillations (PWTOs) with periods of 4–19 days. We find that (1) these PWTOs occur more frequently in the months from May to October. They are consistent with the summertime preference of middle latitude ionospheric electron density oscillations noted in other studies. (2) The month-to-month variations in PWTOs show phase changes between MH and XL, switching from anti-phase to in-phase when PWTO periods vary from short to long. (3) Typical PWTOs show annual and semiannual variations. The relative intensity of annual over semiannual components for PWTOs is different between XL and MH. (4) Magnetic storms and substorms have little influences on the annual and semiannual variations of the typical PWTOs amplitudes. (5) Meridional wind PWTOs with typical periodicity bands around 5-, 8-, and 16-days appear to be correlated to both solar wind speed and Kp oscillations, suggesting a possible influence of the solar wind Co-rotation Interaction Regions (CIR) on neutral wind dynamics.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 4
    Publication Date: 2015-07-01
    Description: An 11 year (1989-1995, 2010-2013) nighttime thermospheric wind (at ~250 km) data set from Fabry-Perot Interferometer (FPI) at Millstone Hill (MH, 42.6°N, 71.5°W) is used to investigate multi-day oscillations (6-30 days) in the thermospheric nighttime winds. Dependencies of multi-day oscillations on solar radiation (F10.7), solar wind speed (SW), and geomagnetic activity (Kp) are determined. We found (1) there exist prominent quasi-27-day oscillations in the thermospheric zonal (meridional) wind, which appears to be more correlated to the same periodic oscillations in Kp and SW than in F10.7 during the solar maximum (solar declining phase and minimum); (2) Quasi-13.5-day oscillations in the zonal wind occur during the solar maximum and increasing phases and are also more correlated to the same periodic oscillations in Kp and SW; and (3) in general the correlations of the multi-day oscillations in the thermospheric winds are more correlated with Kp and SW than F10.7. Our analyses also show that the zonal wind is more sensitive to SW than the meridional wind. We further find: (4) for high F10.7, the pre-midnight zonal wind is more westward toward increasing SW; for low F10.7, the post-midnight zonal wind is also more westward toward increasing SW; and (5) meridional winds tend to be more southward with increasing SW for medium and high F10.7.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 5
    Publication Date: 2018-02-01
    Print ISSN: 1365-1609
    Electronic ISSN: 1873-4545
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Published by Elsevier
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