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1.
Transverse secondary circulations involving surface convergence, observed in a well-mixed estuary in North Wales, are made visible by the collection of surface material along an axial line which extends continuously for many kilometres through the estuary. The circulation and axial convergence, however, are seen only during the flood phase of the tide and no similar behaviour has been observed during the ebb phase.Convergent circulations in the estuary are associated with small but steady transverse density gradients in the cross-section, produced by non-uniform advection of the longitudinal gradient through the channel. A diagnostic model, using measured mean distributions of cross-sectional density, indicates surface transverse velocities (~0.1 ms?1) similar to those observed in the estuary. The model further predicts appreciable transverse divergent currents at a fractional depth of 0.75: a prediction which has been tested in the estuary using a vertical array of accurately resolving current direction indicators. 相似文献
2.
This study employed Slack-based measure (SBM), Meta-frontier analysis, and Malmquist–Luenberger index (MLI) approaches to measure energy efficiency (EE), production technology heterogeneity, and energy productivity variation and its main determinants in developed and developing G20 countries for the period 1995–2020. The study's findings are: (i) Average EE for G20 countries is 0.8577, but still has an improvement potential of 14.23 percent. (ii) Developed countries have a higher average EE than developing (0.8927 > 0.8290). Results further revealed that energy efficiency scores in Argentina, Australia, Brazil, France, Saudi Arabia, South Africa, the US, the UK, and Korea are>1. (iii) Technology gap ratio (TGR) value in developed countries is higher than in developing (0.9869 > 0.6801), indicating that developed countries have advanced energy technologies superiority. The average MLI is less than one, showing a decline in energy productivity mainly due to a decline in technical efficiency, as EC < TC. (iv) Developed G20 countries get 0.64 percent aggregate growth in energy productivity as their MLI score is 1.0064, mainly due to technological growth (TC = 1.0161). Developing G20 countries, on the other hand, witnessed a decline in their energy productivity during 1995–2020, as MLI = 0.9925 > 1, designating that, on average, there is a 0.75 % decline in MLI. 相似文献
3.
选取四川省汶川至马尔康公路线的磨子沟作为试验对象,采用弯道超高法推算其泥石流流速。进而可以计算出该次泥石流的平均流量,为公路的改建工程提供设计依据。经过实地调查,用此方法计算磨子沟2005年8月17日暴发的泥石流流速为4.4m/s。同其他流速方法计算的结果相比较,前者值偏大,且偏向于工程安全值。弯道超高法可以解决泥石流观测的局限性和泥石流发生的不可重复性。此方法简便易行,对泥石流防治工程具有一定的实用价值。 相似文献
4.
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综合介绍了信息高速公路及国家空间信息基础设施的基本情况、地理科学的信息化和地理信息系统的发展趋势和特点,并说明了信息高速公路对地理科学信息化及地球科学研究及应用的影响。 相似文献
6.
7.
M. Koch-Müller P. Dera Y. Fei H. Hellwig Z. Liu J. Van Orman R. Wirth 《Physics and Chemistry of Minerals》2005,32(5-6):349-361
We synthesized superhydrous phase B (shy-B) at 22 GPa and two different temperatures: 1200°C (LT) and 1400°C (HT) using a
multi-anvil apparatus. The samples were investigated by transmission electron microscopy (TEM), single crystal X-ray diffraction,
Raman and IR spectroscopy. The IR spectra were collected on polycrystalline thin-films and single crystals using synchrotron
radiation, as well as a conventional IR source at ambient conditions and in situ at various pressures (up to 15 GPa) and temperatures
(down to −180°C). Our studies show that shy-B exists in two polymorphic forms. As expected from crystal chemistry, the LT
polymorph crystallizes in a lower symmetry space group (Pnn2), whereas the HT polymorph assumes a higher symmetry space group (Pnnm). TEM shows that both modifications consist of nearly perfect crystals with almost no lattice defects or inclusions of additional
phases. IR spectra taken on polycrystalline thin films exhibit just one symmetric OH band and 29 lattice modes for the HT
polymorph in contrast to two intense but asymmetric OH stretching bands and at least 48 lattice modes for the LT sample. The
IR spectra differ not only in the number of bands, but also in the response of the bands to changes in pressure. The pressure
derivatives for the IR bands are higher for the HT polymorph indicating that the high symmetry form is more compressible than
the low symmetry form. Polarized, low-temperature single-crystal IR spectra indicate that in the LT-polymorph extensive ordering
occurs not only at the Mg sites but also at the hydrogen sites. 相似文献
8.
This paper comprehensively analyzes the characteristics and cause of the inshore intensification of super typhoon "Hato", the 13 th super typhoon in 2017. The aspects of typhoon structure, evolution of large-scale circulation and physical quantity field are analyzed using observation data from the Guangdong Automatic Station, Shenzhen Doppler Radar data, NCEP 1°×1° reanalysis data, NCEP 0.25°×0.25° sea surface temperature(SST) data, etc.Additionally, in order to investigate the influence of SST change on the intensity of "Hato", the WRF model and ECMWF 0.125°×0.125° reanalysis data are combined to conduct 3 sensitivity tests on"Hato". The results show that the favorable conditions for inshore intensification of "Hato"included the strengthening and westward extension of the subtropical high, continuous increase of low level moisture transport, an anomalous warm SST area north of 20°N in the South China Sea, an extreme divergence value in the northern South China Sea exceeding 6 ×10-5 s-1, and vertical environmental wind shear between 1.1 m/s-4.8 m/s. The intensity of"Hato"was very sensitive to changes in SST. When the SST rose or dropped by 2℃, the minimum central pressure of the typhoon changed by about 13 hPa or 11 hPa,respectively. SST indirectly influenced the intensity of the typhoon through affecting latent heat transport and sensible heat transport. 相似文献
9.
Phiros Shah R. Sajeev K. J. Thara Grinson George Muhammad Shafeeque S. Akash 《Marine Geodesy》2019,42(1):64-84
An attempt has been made to develop a holistic understanding of upwelling and downwelling along the south-west coast of India. The main objective was to elucidate the roles of different forcings involved in the vertical motion along this coast. The south-west coast of India was characterized by upwelling during the south-west monsoon (May to September) and by downwelling during the north-east monsoon and winter (November to February). The average vertical velocity calculated along the south-west coast from the vertical shift of the 26?°C isotherm is 0.57?m/day during upwelling and 0.698?m/day during downwelling. It was concluded that upwelling along the south-west coast of India is driven by offshore Ekman transport due to the alongshore wind, Ekman pumping, horizontal divergence of currents and by the propagation of coastally trapped waves. Whereas downwelling along the coast is driven only by convergence of currents and the propagation of coastally trapped Kelvin waves. Along the west coast of India, the downwelling-favorable Kelvin waves come from the equator and upwelling-favorable waves come from the Gulf of Mannar region. 相似文献
10.
A steady state model of the Somali current including forcing by both the curl and the divergence of the wind stress is discussed.
The model equations are linear, but the results presented are for the one nonlinear case. The grid resolution was 12 km in
the zonal and 24 km in the meridional direction. The streamfunction and velocity potential of the current are presented for
forcing by divergence and compared with a situation when only the curl is present. The results indicate that a two-gyre system
appears in July, a representative month for the summer monsoon, only when divergence is included. Computations with available
data indicate that the divergence is comparable in magnitude to the curl near the location of the Somali current. The model
produces three other important features: (i) strong upwelling off the east coast of Africa, (ii) downwelling over central
Arabian sea and (iii) a strong eastward current in the upper layer towards the interior of the Arabian sea near 12°N. 相似文献