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111.
On the spatial relationship between landslides and causative factors on Lantau Island, Hong Kong 总被引:8,自引:0,他引:8
This paper presents a statistical approach to study the spatial relationship between landslides and their causative factors at the regional level. The approach is based on digital databases, and incorporates such methods as statistics, spatial pattern analysis, and interactive mapping. Firstly, the authors propose an object-oriented conceptual model for describing a landslide event, and a combined database of landslides and environmental factors is constructed by integrating the various databases within such a conceptual framework. The statistical histogram, spatial overlay, and dynamic mapping methods are linked together to interactively evaluate the spatial pattern of the relationship between landslides and their causative factors. A case study of an extreme event in 1993 on Lantau Island indicates that rainfall intensity and the migration of the center of the rainstorm greatly influence the occurrence of landslides on Lantau Island. A regional difference in the relationship between landslides and topography is identified. Most of the landslides in the middle and western parts of the island occurred on slopes with slope angles of 25–35°, while in the eastern part, the corresponding range is 30–35°. Overlaying landslide data with land cover reveals that a large number of landslides occurred in the bareland and shrub-covered area, and in the transition zones between different vegetation types. The proposed approach can be used not only to analyze the general characteristics of such a relationship, but also to depict its spatial distribution and variation, thereby providing a sound basis for regional landslide prediction. 相似文献
112.
Z. M. Sawan L. I. Hanna Gh. A. Gad El Karim W. L McCuistion 《Journal of Arid Environments》2002,52(4):499
Fruiting of cotton plant is determined and influenced by cultivar, climatic conditions, management practices and pests. An understanding of the flowering and boll retention patterns of cotton cultivars can contribute to more efficient and economical crop management. The objective of this investigation was to study the effect of various climatic factors on flower and boll production of Egyptian cotton. This could be used in formulating advanced predictions of the effect of certain climatic conditions on the production of Egyptian cotton. Two uniform field trials, using cotton Gossypium barbadense cv. Giza 75 were carried out in 1992 and 1993 at the Agricultural Research Station, Agricultural Research Center, Ministry of Agriculture, Giza, Egypt, to investigate the relationships between climatic factors, flower and boll production. Climatic factors included maximum and minimum air temperatures along with their difference, evaporation, surface soil temperature (grass temperature or green cover temperature) at 0600 and 1800 h°C−1, sunshine duration, maximum and minimum humidity and wind speed. The effects of climatic factors on flower and boll production were quantified in the absence of water and nutritional deficits and damage effects of insects. Results obtained indicate that evaporation, sunshine duration, humidity, surface soil temperature at 1800 h, and maximum air temperature, were the important climatic factors that significantly affect flower and boll production of Egyptian cotton. Consequently, applying appropriate specific cultural practices that minimize the deleterious effect of these factors will lead to an improvement in cotton yield. 相似文献
113.
M. B. Liu G. R. Liu K. Y. Lam Z. Zong 《Fragblast: International Journal for Blasting and Fragmentation》2003,7(3):181-202
Shaped charges are widely applied in the defense industry and civil engineering for penetrating hardened targets. Simulations of shaped charges are generally based on traditional grid-based numerical methods. Different from the existing literature, the SPH method is applied in this paper to simulate the detonation process of shaped charge explosive. The combination of the meshless, Lagrangian and particle nature inherent in the SPH method is very attractive in dealing with large deformations and large inhomogeneities in extremely transient situations such as detonation process. The SPH method and some related numerical aspects are briefly discussed first, followed by applications in simulating shaped charge detonations. The effects of different detonation cavity angles and different charge head lengths are investigated. The results demonstrate that major shaped charge detonation phenomena are captured with revealing observations. 相似文献
114.
Detailed palaeomagnetic and rock magnetic analyses provide improved palaeomagnetic results from 23 sites in the Borgmassivet intrusions in the Ahlmannryggen region of Dronning Maud Land, East Antarctica. These intrusions are of similar age to their host, the ca. 1130 Ma Ritscherflya Supergroup (RSG). A mean direction of D=235.4°, I=−7.6° with k=45.9 and α95=4.5° was obtained from this study. When combined with previously reported results from 11 sites in the same region, including sites from the Ritscherflya Supergroup, it gives an overall mean direction for 34 sites from the igneous suite with D=236.5°, I=−3.6°, k=27.9 and α95=4.8°. Isothermal remanent magnetization (IRM) experiments on several specimens suggest magnetite or titanomagnetite as the primary remanence carrier, while high temperature magnetic susceptibility experiments indicate the presence of single domain particles. These observations, together with field evidence and the high coercivities and unblocking temperatures, support a primary origin for the observed characteristic remanence. The Borgmassivet palaeomagnetic pole lies at 54.5°E, 8.3°N with A95=3.3°. If Antarctica is moved to its Gondwanan position adjacent to southeast Africa, the Borgmassivet pole (BM) coincides with that of the African well-established, well-dated (1100 Ma) Umkondo Large Igneous Province pole, supporting the hypothesis that the Grunehogna craton of Dronning Maud Land was part of the Kalahari craton of southern Africa at ca. 1100 Ma. 相似文献
115.
From geometry to dynamics of microstructure: using boundary lengths to quantify boundary misorientations and anisotropy 总被引:1,自引:0,他引:1
John Wheeler Z. Jiang D. J. Prior J. Tullis M. R. Drury P. W. Trimby 《Tectonophysics》2003,376(1-2):19-35
The microstructure of a quartzite experimentally deformed and partially recrystallised at 900 °C, 1.2 GPa confining pressure and strain rate 10−6/s was investigated using orientation contrast and electron backscatter diffraction (EBSD). Boundaries between misoriented domains (grains or subgrains) were determined by image analysis of orientation contrast images. In each domain, EBSD measurements gave the complete quartz lattice orientation and enabled calculation of misorientation angles across every domain boundary. Results are analysed in terms of the boundary density, which for any range of misorientations is the boundary length for that range divided by image area. This allows a more direct comparison of misorientation statistics between different parts of a sample than does a treatment in terms of boundary number.The strain in the quartzite sample is heterogeneous. A 100×150 μm low-strain partially recrystallised subarea C was compared with a high-strain completely recrystallised subarea E. The density of high-angle (>10°) boundaries in E is roughly double that in C, reflecting the greater degree of recrystallisation. Low-angle boundaries in C and E are produced by subgrain rotation. In the low-angle range 0–10° boundary densities in both C and E show an exponential decrease with increasing misorientation. The densities scale with exp(−θ/λ) where λ is approximately 2° in C and 1° in E; in other words, E has a comparative dearth of boundaries in the 8–10° range. We explain this dearth in terms of mobile high-angle boundaries sweeping through and consuming low-angle boundaries as the latter increase misorientation through time. In E, the density of high-angle boundaries is larger than in C, so this sweeping would have been more efficient and could explain the relative paucity of 8–10° boundaries.The boundary density can be generalised to a directional property that gives the degree of anisotropy of the boundary network and its preferred orientation. Despite the imposed strain, the analysed samples show that boundaries are not, on average, strongly aligned. This is a function of the strong sinuosity of high-angle boundaries, caused by grain boundary migration. Low-angle boundaries might be expected, on average, to be aligned in relation to imposed strain but this is not found.Boundary densities and their generalisation in terms of directional properties provide objective measures of microstructure. In this study the patterns they show are interpreted in terms of combined subgrain rotation and migration recrystallisation, but it may be that other microstructural processes give distinctive patterns when analysed in this fashion. 相似文献
116.
Numerical simulation of a South China Sea typhoon Leo (1999) 总被引:6,自引:0,他引:6
K.-H. Lau Z.-F. Zhang H.-Y. Lam S.-J. Chen 《Meteorology and Atmospheric Physics》2003,83(3-4):147-161
Summary ?A South China Sea typhoon, Leo (1999), was simulated using the Penn State/NCAR mesoscale model MM5 with the Betts-Miller
convective parameterization scheme (BMEX). The simulation had two nested domains with resolutions at 54 and 18 km, and the
forecast duration was 36 hours. The model was quite successful in predicting the track, the rapid deepening, the central pressure,
and the maximum wind speed of typhoon Leo as verified with reports from the Hong Kong Observatory (HKO). The structure of
the eye, the eye wall, and the spiral convective cloud band simulated in the model are found to be comparable to corresponding
features identified in satellite images for the storm, and also with those reported by other authors.
A trajectory analysis was performed. Three kinds of trajectory were found: (1) spirally rising trajectories near the eye wall;
(2) spirally rising/descending trajectories in the convective/cloud free belt; (3) straight and fast rising trajectories in
a heavy convection zone along one of the cloud bands on the periphery of the tropical cyclone.
Both the HKO and the U.S. Joint Typhoon Warning Center (JTWC) reported the rapid deepening of Leo started around 00 UTC 29
April. In the model, the eye was first formed in the lower troposphere, and it extended to the upper troposphere within a
few hours. We speculate that the spin-up of cyclonic rotation in the low-level eye enhanced the positive vorticity along the
low-level eye wall. The positive vorticity was then transported to the upper troposphere by convection, leading to an extension
and growth of the eye into the upper troposphere.
To examine the impact of convective parameterization scheme (CPS) on the simulation, the Grell scheme (GLEX) was also tested.
The GLEX predicted a weaker typhoon with a wilder eye that extended not as high up in the upper troposphere as BMEX. The different
structures of the eye between the BMEX and GLEX suggest that the mesoscale features of the eye are dependent on the convection.
In other words, the vertical and horizontal distribution of convective heating is essential to the development and structure
of the eye.
Received December 18, 2001; accepted May 7, 2002
Published online: March 20, 2003 相似文献
117.
Construction of Green's function to the external Dirichlet boundary-value problem for the Laplace equation on an ellipsoid of revolution 总被引:1,自引:0,他引:1
Green's function to the external Dirichlet boundary-value problem for the Laplace equation with data distributed on an ellipsoid
of revolution has been constructed in a closed form. The ellipsoidal Poisson kernel describing the effect of the ellipticity
of the boundary on the solution of the investigated boundary-value problem has been expressed as a finite sum of elementary
functions which describe analytically the behaviour of the ellipsoidal Poisson kernel at the singular point ψ = 0. We have
shown that the degree of singularity of the ellipsoidal Poisson kernel in the vicinity of its singular point is of the same
degree as that of the original spherical Poisson kernel.
Received: 4 June 1996 / Accepted: 7 April 1997 相似文献
118.
A key ingredient in simulation of flow in porous media is accurate determination of the velocities that drive the flow. Large‐scale irregularities of the geology (faults, fractures, and layers) suggest the use of irregular grids in simulation. This paper presents a control‐volume mixed finite element method that provides a simple, systematic, easily implemented procedure for obtaining accurate velocity approximations on irregular (i.e., distorted logically rectangular) block‐centered quadrilateral grids. The control‐volume formulation of Darcy’s law can be viewed as a discretization into element‐sized “tanks” with imposed pressures at the ends, giving a local discrete Darcy law analogous to the block‐by‐block conservation in the usual mixed discretization of the mass‐conservation equation. Numerical results in two dimensions show second‐order convergence in the velocity, even with discontinuous anisotropic permeability on an irregular grid. The method extends readily to three dimensions. 相似文献
119.
Si K- and L-edge ELNES spectroscopy and multiple-scattering (MS) calculations are used to examine mixed Si coordination compounds
varying in SiVI:SiIV ratio. As in previous studies, the edges are influenced mainly by silicon coordination (tetrahedral vs. octahedral), as supported
by the MS calculations. We demonstrate two methods semi-quantitatively to extract the value of SiVI/(SiVI+SiIV): (1) A linear relationship between the L2,3-L1 splitting and SiVI/(SiVI+SiIV) is observed, (2) a fitting method based on the coaddition of reference tetrahedral and octahedral Si spectra is applied
to both Si K- and L-edge ELNES spectra.
Received: February 10, 1997 / Revised, accepted: May 23, 1997 相似文献
120.
Acid mine drainage (AMD) occurs when sulfide minerals are exposed to an oxidizing environment. Most of the methods for preventing
AMD are either short-term or high cost solutions. Coating with iron phosphate is a new technology for the abatement of AMD.
It involves treating the sulfide with a coating solution composed of H2O2, KH2PO4, and sodium acetate as a buffer agent. The H2O2 oxidizes the sulfide surface and produces Fe3+ so that iron phosphate precipitates as a coating on the sulfide surface. Experiments performed under laboratory conditions
prove that an iron phosphate coating can be established on pyrrhotite surfaces with optimal concentrations of the coating
solution in the range of: 0.2M/0.01M H2O2, 0.2M KH2PO4, and 0.2M sodium acetate NaAc, depending on the experimental scale. Iron phosphate coating may be a long-term solution to
the problem of AMD. The method would be easy to implement; the reagent cost, however, is not low enough, although it is lower
than the conventional treatment with lime.
Received: 30 March 1995 · Accepted: 6 September 1995 相似文献