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111.
Wang Wenli Institute of Natural History Beijing Natural History Museum Yang Zunyi 《《地质学报》英文版》1993,67(3)
A new insect family Liaoximordellidae (fam. nov.) has been named for a well-preserved specimen which was collected from the Upper Jurassic outcropping west of Daxinfangzi Village, Lingyuan County, Liaoning Province. The specimen can not be put into Mordellidae or Praemordellidae because it possesses some original and intermediate characters in morphology. It serves the study of mordellid evolution. Besides, the fossil group associated with the insect is important for the stratigraphic division of the Mesozoic in western Liaoning. 相似文献
112.
Rahim Barzegar Asghar Asghari Moghaddam Amir Hossein Nazemi Jan Adamowski 《Environmental Earth Sciences》2018,77(16):597
Rapid population growth, industrialization, and agricultural expansion in the Khoy area (northwestern Iran) have led to its dependence on groundwater and degradation of groundwater quality. This study attempts to decipher the major processes and factors that degrade the groundwater quality of the Khoy plain. For this purpose, 54 groundwater samples from unconfined and confined aquifers of the plain were collected in July 2017 and analyzed for major cations and anions (Na, K, Ca, Mg, HCO3, SO4, and Cl), minor ions (NO3 and F), and Al. Magnesium and bicarbonate were identified as the dominant cation and anion, respectively. Several ionic ratios and geochemical modeling using PHREEQC indicated that the most important hydrogeochemical processes to affect groundwater quality in the plain were weathering and dissolution of evaporitic and silicate minerals, mixing, and ion exchange. There were smaller effects from evaporation and anthropogenic factors (e.g., industries). Results showed that the high salinity of the groundwater in the northeast area of the plain was due to the high solubility of the evaporitic minerals, e.g., halite and gypsum. Reverse ion exchange and the contribution of mineral dissolution were more significant than ion exchange in the northeastern part of the plain. Elevated salinity of the groundwater in the southeast was attributed mostly to reverse ion exchange and somewhat to evaporation. 相似文献
113.
Wang Shaowu 《大气科学进展》1984,1(1):7-29
The most effective technique in long-range weather forecasting in China is teleconnection. Summer rainfall and temperatures are closely correlated to the preceding winter 500 mb heights over the Northern Hemisphere and sea surface temperatures over the North Pacific, so the former can be predicted from the latter. This kind of connection is called rhythm. In this paper, four examples of rhythm are outlined. The manifestation of rhythm and its universal significance is demonstrated. The mechanism of rhythm is discussed. 相似文献
114.
Heterogeneous characteristics of streambed saturated hydraulic conductivity of the Touchet River,south eastern Washington,USA 总被引:1,自引:0,他引:1
Randal Leek Joan Q. Wu Li Wang Timothy P. Hanrahan Michael E. Barber Hanxue Qiu 《水文研究》2009,23(8):1236-1246
Traditionally a streambed is treated as a layer of uniform thickness and low saturated hydraulic conductivity (K) in surface‐ and ground‐water studies. Recent findings have shown a high level of spatial heterogeneity within a streambed and such heterogeneity directly affects surface‐ and ground‐water exchange and can have ecological implications for biogeochemical transformations, nutrient cycling, organic matter decomposition, and reproduction of gravel spawning fish. In this study a detailed field investigation of K was conducted in two selected sites in Touchet River, a typical salmon spawning stream in arid south eastern Washington, USA. In‐stream slug tests were conducted to determine K following the Bouwer and Rice method. For the upper and lower sites, each 50 m long and 9 m wide and roughly 20 m apart, a sampling grid of 5 m longitudinally and 3 m transversely was used. The slug tests were performed for each horizontal coordinate at 0·3–0·45, 0·6–0·75, 0·9–1·05 and 1·2–1·35 m depth intervals unless a shallower impenetrable obstruction was encountered. Additionally, water levels were measured to obtain vertical hydraulic gradient (VHG) between each two adjacent depth intervals. Results indicated that K ranged over three orders of magnitude at both the upper and lower sites and differed between the two sites. At the upper site, K did not differ significantly among different depth intervals based on nonparametric statistical tests for mean, median, and empirical cumulative distribution, but the spatial pattern of K varied among different depth intervals. At the lower site, K for the 0·3–0·45 m depth interval differed statistically from those at other depth intervals, and no similar spatial pattern was found among different depth intervals. Zones of upward and downward water flow based on VHG also varied among different depth intervals, reflecting the complexities of the water flow regime. Detailed characterization of the streambed as attempted in this study should be helpful in providing information on spatial variations of streambed hydraulic properties as well as surface‐ and ground‐water interaction. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
115.
2.5-D modeling and inversion techniques are much closer to reality than the simple and traditional 2-D seismic wave modeling
and inversion. The sensitivity kernels required in full waveform seismic tomographic inversion are the Fréchet derivatives
of the displacement vector with respect to the independent anisotropic model parameters of the subsurface. They give the sensitivity
of the seismograms to changes in the model parameters. This paper applies two methods, called ‘the perturbation method’ and
‘the matrix method’, to derive the sensitivity kernels for 2.5-D seismic waveform inversion. We show that the two methods
yield the same explicit expressions for the Fréchet derivatives using a constant-block model parameterization, and are available
for both the line-source (2-D) and the point-source (2.5-D) cases. The method involves two Green’s function vectors and their
gradients, as well as the derivatives of the elastic modulus tensor with respect to the independent model parameters. The
two Green’s function vectors are the responses of the displacement vector to the two directed unit vectors located at the
source and geophone positions, respectively; they can be generally obtained by numerical methods. The gradients of the Green’s
function vectors may be approximated in the same manner as the differential computations in the forward modeling. The derivatives
of the elastic modulus tensor with respect to the independent model parameters can be obtained analytically, dependent on
the class of medium anisotropy. Explicit expressions are given for two special cases—isotropic and tilted transversely isotropic
(TTI) media. Numerical examples are given for the latter case, which involves five independent elastic moduli (or Thomsen
parameters) plus one angle defining the symmetry axis. 相似文献
116.
A multi-equation spatial econometric model,with application to EU manufacturing productivity growth 总被引:1,自引:0,他引:1
Bernard Fingleton 《Journal of Geographical Systems》2007,9(2):119-144
A multi-equation spatial econometric model is used to explain variations across EU regions in manufacturing productivity growth
based on recent theoretical developments in urban economics and economic geography. The paper shows that temporal and spatial
parameter homogeneity is an unrealistic assumption, contrary to what is typically assumed in the literature. Constraints are
imposed on parameters across time periods and between core and peripheral regions of the EU, with the significant loss of
fit providing overwhelming evidence of parameter heterogeneity, although the final model does highlight increasing returns
to scale, which is a central feature of contemporary theory.
相似文献
117.
Assessing landslide movements in volcanic islands using near-shore marine geophysical data: south Pico island,Azores 总被引:1,自引:0,他引:1
Marine geophysical data from around the submarine flanks of volcanic islands can potentially help to resolve whether large-scale
instability of an edifice has been geologically recently active. We use geophysical data to investigate part of the coast
of Pico Island of the Azores where, above sea-level, a major slump of Topo volcano has been interpreted previously from arcuate
escarpments and a rugged irregular topography seaward of them. Multibeam echo-sounder data collected offshore of this feature
show remarkably little evidence for slump fault movements in the island's submarine slope. Mid-slope benches, like those associated
with the Hilina Slump of Kilauea, are absent. The high-resolution data extends onto the island's shelf, allowing us to evaluate
evidence for continuing activity there. In particular, as the shelf's rock platform will have been last modified by surf erosion
during the postglacial period of sea-level transgression, it provides a reference surface of intermediate age (7–19 ka) that
can potentially reveal whether any movements occurred in pre-historic times. Where the arcuate escarpments are continued offshore,
the modern seabed shows no bathymetric evidence for active faults where the shelf rock platform crops out in the multibeam
data. Elsewhere, mobile shelf sediments could be disguising evidence for active faulting so we examined boomer profiles able
to image the rock platform beneath them. The data reveal a platform that is steep (6.6°) compared with the dips of platforms
that we have studied previously around the coast of adjacent Faial Island and steeper than the platform outside the proposed
slump. This suggests that it was created by coastal erosion over a shorter period and hence is consistent with a younger age
of the coastline. As with the multibeam data, where escarpments are continued offshore onto the shelf, the rock surface imaged
with these boomer data also shows no clear evidence of major slump-related fault displacements. This study therefore illustrates
how high-resolution boomer seismic and multibeam data could usefully contribute to hazard assessment of volcanic islands,
by helping to evaluate areas with no historical movements. Explanations to reconcile the onshore and offshore data here are
also put forward. 相似文献
118.
INTRODUCTIONAquiculturearearedtidesignalsoceanpollutionanddisaster.Althoughenvironmentscientistshaveconductedmanyin depthresearchesonthecauseandformationmechanismofredtide ,manyofitsaspectsarestillunknownbecauseredtideisacomplexphenomenonandtheecologic… 相似文献
119.
This article describes a novel algorithm for cosmic‐ray rejection in single spectroscopic CCD images. This algorithm is based on a variation of template matching. It focuses on identifying those pixels belong to spectra, while other conventional algorithms tried to locate the cosmic‐ray hits directly. The main principle is applying template matching to find suspicious blocks, which is followed by surface patching to locate the legitimate pixels accurately. Therefore, the rest pixels are the ones corrupted by cosmic‐ray hits. Meanwhile, almost all the parameters are automatically extracted from the images. Examples of its performance are given for both simulated and observed images. It shows an advantage of significantly low false alarm rate with relatively high detection rate (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
120.
If the upstream boundary conditions are prescribed based on the incident wave only, the time-dependent numerical models cannot effectively simulate the wave field when the physical or spurious reflected waves become significant. This paper describes carefully an approach to specifying the incident wave boundary conditions combined with a set sponge layer to absorb the reflected waves towards the incident boundary. Incorporated into a time-dependent numerical model, whose governing equations are the Boussinesq-type ones, the effectiveness of the approach is studied in detail. The general boundary conditions, describing the down-wave boundary conditions are also generalized to the case of random waves. The numerical model is in detail examined. The test cases include both the normal one-dimensional incident regular or random waves and the two-dimensional oblique incident regular waves. The calculated results show that the present approach is effective on damping the reflected waves towards the incident wave boundary. 相似文献