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1.
Bedford RD 《GeoJournal》1988,16(2):179-192
May 1987 is a month that will not be forgotten in the South Pacific. The first of two military coups d'etat led by Colonel Sitiveni Rabuka not only transformed the course of post-colonial political development in Fiji, but this event also had profound implications for international relations in the region. Co-incidentally, May 1987 was also the month when detailed results of Fiji's second national population census since Independence in 1970 became available. The 1986 census documents Fiji's population on the eve of a political revolution which has the potential to cause significant economic and social change. The demographic process most likely to be affected in the short-term by the coups is population movement, both within Fiji and to overseas destinations. This: paper examines developments in population movement between 1970 and 1986 with particular reference to an acceleration in levels of migration overseas by Indians and an exodus of Fijians from rural village communities for towns on Viti Levu and Vanua Levu. Trends in internal and international migration are evaluated at a range of spatial scales — national, regional and local. Some speculation on the effect of political and economic changes since May 1987 on these population movements attempts to provide a contemporary perspective on demographic developments over the last 15 years.  相似文献   

2.
在4月16日举行的新农村基本建设优化论坛上,中国基本建设优化研究会与韩国新乡村运动中央会举行了合作签字仪式,围绕新农村建设,双方表示将进一步加强交流与合作。就如何合理引进韩国新乡村运动成功经验、为中国新农村建设服务问题,本刊记者采访了韩国每日产业株式会社代表理事、会长朴梓援先生和韩国《每日经济》日报社中国team部长尹炯植先生。  相似文献   

3.
JANE K. HART 《Sedimentology》2006,53(1):125-146
The subglacial processes at Briksdalsbreen, Norway, are examined by a combination of sedimentology, thin section and scanning electron microscope (SEM) analysis of till samples from an exposed subglacial surface and from beneath the glacier. Studies of a fluted surface indicate that subglacial deformation is occurring on a field scale with flutes forming behind most clasts 0·6 m high. At the thin section scale (0·014–2·0 mm) it is seen that deformation is by rotation and attenuation and is dependent on till texture. At the SEM scale (0·1–0·4 mm) it is seen that erosion is controlled by abrasion and percussion which produces distinct grain ‘styles’ as part of an erosional continuum. Overall it is shown that rotation and attenuation is a dominant process at all scales and that the clast interactions associated with different scale perturbations within the shear zone control erosion and deposition, as well as landform and fabric production.  相似文献   

4.
A. Moreno 《Tectonophysics》1986,130(1-4):159-165
The Earth surface slide movement at Soledad is a mountain-slide type of movement. Estimations of the thickness of the layer which is moving range between 10 and 100 m. There is no proof that the movement is water induced, but it could be influenced by the water household. The slope of the slide area is H: D = 1: 2.

The height difference in the moving area studied, according to this paper, is 1 km. The actual rate of movement is about 12 cm/yr.  相似文献   


5.
Fugacities of H2, N2, O2, CH4, H2O, H2S, NH3, CO, and CO2 are calculated on the basis of the extrapolation of the caloric properties, and those of the compressibility of substances into the region of pressures up to 2 Mbar and of temperatures up to 4000K. Several equilibrium mineralogical reactions are calculated. The most probable sequence of decreasing the magnitudes of the equilibrium molar fractions (masses) of these gases in the lower mantle of the earth is predicted.  相似文献   

6.
A procedure is described whereby the effect of extra components on the plotting positions of minerals in projected phase diagrams may be accounted for rigorously. The method employs the equilibrium constraints of the mineral assemblage to extrapolate the compositions of the minerals to where the values of the extra components approach 0. The same procedure may also be used to extrapolate the compositions of natural assemblages over isothermal, isobaric composition diagrams or polythermal, polybaric diagrams.Examples from typical garnet-bearing pelite assemblages indicate that the extra components MnO and CaO dramatically shift the compositions of coexisting phases to lower Fe/Mg, even where the phase itself (e.g. chlorite or biotite) does not contain appreciable quantities of the extra component. Recognition of, and correction for, this effect is critical if projected phase diagrams are to be compared with experimentally calibrated phase diagrams in the chemical subsystem.  相似文献   

7.
The elastic constants of a crystal under stress, defined as the second derivative of the crystal free energy with respect to strain, require a correction related to the static pressure at non-zero pressures. The corrections required for the elastic constants calculated by the free energy minimisation code PARAPOCS are described and tested by comparison with the elastic constants calculated numerically by applying small stresses in the appropriate orientations to simulated crystals of fluorite, forsterite, α-quartz and albite. The corrected elastic constants are then used to investigate the extrapolation of the bulk and shear moduli (and hence also the seismic wave velocities V p and V s) of β-spinel and forsterite to upper mantle pressures. A Murnaghan equation, thirdorder Eulerian finite strain equation, second order polynomial equation and a logistic equation were all fitted to the simulated bulk and shear moduli between 0 and 3 GPa pressure. The parameters derived for these equations are used to extrapolate the bulk and shear moduli to 14 GPa and the results are compared to the simulated high pressure moduli. Over this pressure range, the second order polynomial provides the best extrapolation of the bulk modulus, but the use of the logistic equation results in the best extrapolation of the shear modulus.  相似文献   

8.
Wang  Xing  Wang  Jianhong  Miao  Chunsheng  Zeng  Kang 《Natural Hazards》2020,103(1):903-921
Natural Hazards - Currently, using common meteorological data for downburst identification and early warning lacks feasibility. Therefore, a method based on the Doppler weather radar is proposed in...  相似文献   

9.
When fluid flows in porous media under subsurface conditions, significant deformation can occur. Such deformation is dependent on structural and phase characteristics. In this paper, we investigate the effect of multiphase flow on the deformation of porous media at the pore scale by implementing a strongly coupled partitioned solver discretized with finite volume (FV) technique. Specifically, the role of capillary forces on grain deformation in porous media is investigated. The fluid and solid subdomains are meshed using unstructured independent grids. The model is applied for solving multiphase coupled equations and is capable of capturing pore scale physics during primary drainage by solving the Navier-Stokes equation and advecting fluid indicator function using volume of fluid (VOF) while the fluid is interacting with a nonlinear elastic solid matrix. The convergence of the coupled solver is accelerated by Aitken underrelaxation. We also reproduce geomechanical stress conditions, at the pore scale, by applying uniaxial stress on the solid while simultaneously solving the multiphase fluid-solid interaction problem to investigate the effect of external stress on fluid occupancy, velocity-field distribution, and relative permeability. We observe that the solid matrix exhibits elasto-capillary behavior during the drainage sequence. Relative permeability endpoints are shifted on the basis of the external stress exerted.  相似文献   

10.
Limestone bedrock topography has complex phenomena and highly relief subsurface topography due to the presence of karstic features. Geotechnical and environmental problems arise whenever foundations are established on the surface of the limestone bedrock or within the overburden soils. Geographical information system (GIS) and remote sensing are emerging as powerful techniques widely applicable in natural resources management to detect land use changes and devise strategies based on these changes. The study focuses on using aerial photography for the detection of changes and effects of mining on geomorphology, especially the use of sequential images that allows to detect changes taken place from time to time, by using. Volumetric Surface Movement Spatiotemporal Data Model (VSMSDM) application has been employed to create karst terrain surface movements and visualized 3D information in the Virtual Geographical Information Systems (VGIS). VSMSDM application was implemented by developing prototype of visualization system using with integrated time in the TIN structure. The data have been collected from aerial photography in 1981 and 2004, and the results displayed that the proposed data model is able to view the changing in karst topography to detect significant landscapes and landforms changes.  相似文献   

11.
孙海龙  王德利  陈鑫  王通 《世界地质》2015,34(1):226-231
水层多次波是海上地震勘探过程中的一个重要干扰因素。为压制水层多次波,本文在倾斜模型条件下采用基本的正向延拓方法去除多次波,取得了较好的压制效果。在此基础上实现了弯曲水底情况下正、反向波场延拓方法压制多次波;经对比发现,反向延拓方法克服了复杂水下介质情况下对格林函数求取的干扰,消除多次波效果更好。  相似文献   

12.
In situ measurements of mineral surface evolution during the process of pressure solution are possible with the high brightness of synchrotron X-ray sources. This capability has been explored through the use of newly developed reaction vessels that allow transmission of the incident and scattered X-ray beam through a low atomic weight piston. Several new vessels are described, along with details of computational algorithms that are used to simulate X-ray scattering in this unconventional geometry. Results using calcite (CaCO3) and halite (NaCl) as reactant crystals are presented and compared to other atomic-scale measurements of surface dissolution processes. Calcite was reacted with an unsaturated fluid at 30 bars of pressure for approximately 24 h. During reaction the root mean square surface roughness (σ) evolved from 13.7 Å (± 0.5 Å) to 19.5 Å (± 1.0 Å), giving a roughening rate of: dσ/dt = +6.3 × 10− 5 Å s− 1. This is consistent with other measurements made with free calcite surfaces and is driven almost entirely by chemical disequilibrium. Analysis of the surface ex situ post-reaction gives an identical σ value, showing that the in situ measurements are well-constrained. Experiments also at 30 bars but in a saturated solution indicate that the calcite surface does not significantly roughen, giving the result that pressure solution of calcite at this pressure cannot be monitored in experiments of several days duration. Experiments with halite, a much more reactive phase, in saturated solutions showed the reflectivity profile to be dynamic on a time scale of hours. This experiment was left to reach equilibrium over 108 days and then re-analyzed, showing that σ had increased from 34 Å (± 2 Å) to 41 Å (± 2 Å), giving a roughening rate of: dσ/dt ≤ +6.4 × 10− 7 Å s− 1. This is two orders of magnitude smaller than the calcite roughening rate caused by chemical disequilibrium and provides the first direct in situ atomic-scale measurement of the rate of surface roughening due to pressure solution.  相似文献   

13.
In 1982, sediments contaminated with zinc, cadmium, and copper were dredged from Lake DePue in Illinois and deposited in a diked sediment disposal area (DSDA) that is flooded annually for at least three months. Data from soil and groundwater samples collected at multiple depths within and adjacent to the DSDA indicate vertical movement of the metals in the subsurface, although groundwater outside of the DSDA was not contaminated with any of the metals. Zinc was elevated in almost all of the wells inside the DSDA. Cadmium concentrations were elevated in shallow wells inside the DSDA, while copper was rarely detected in the groundwater. Comparisons of groundwater samples taken within the DSDA under flooded and unflooded conditions suggest that pH and redox conditions controlled metal solubilities. A comparison between soil cores and sediment cores from Lake DePue suggest that zinc was more mobile than cadmium or copper within the DSDA.  相似文献   

14.
李飞  王金安  李鹏飞  黄坤 《岩土力学》2016,37(4):1089-1095
以海石湾矿山地下开采为背景,借助基于连续介质力学的离散元方法--CDEM数值模拟计算方法,对山区下煤层开采过程中不同采动影响模式下覆岩的移动和破坏进行了模拟分析,并结合相似模拟试验与现场岩移监测所得结果,得到了顺坡推动式采动影响模式及逆坡牵引式采动影响模式下,覆岩的移动和破坏形式,并从数值分析和实际观测上验证了高顺坡开采转低逆坡开采时覆岩悬臂梁结构的存在,解释了坡底局部隆起的现象。研究表明,在相同地质条件下,顺坡开采坡顶易发生张拉及剪切破坏,坡底有剪切蠕滑的可能,因此,较逆坡开采对边坡稳定性影响更大。所以在实际生产中宜将上工业广场建于低矮的坡体较完整的逆坡上。  相似文献   

15.
The Druze Marsh is a spring‐fed wetland in northeast Jordan that dried out completely in the late 1980s. This drying and subsequent drop in the water table permitted study of the marsh stratigraphy and a search for prehistoric occupations. In this paper, we combine detailed sedimentological analysis of eight stratigraphic sections in the bed of the former Druze Marsh to reconstruct the landscapes used by hominins since the Middle Pleistocene. The results show that fluctuation in water availability over the past 350 ka had dramatic impacts on the size and depth of the wetlands. Pleistocene occupations in the Druze Marsh correspond to relatively dry climatic conditions when the wetland was reduced in size, suggesting the Druze Marsh acted as a desert refugium for hominins during adverse climatic conditions. Such refugia have important implications for hominin demography, continuity, and/or extinction in the Syro‐Arabian Desert. Moreover, the Druze Marsh is positioned at the north end of the Wadi Sirhan depression that connects the Levantine Corridor to the west and Arabian Peninsula to the southeast. Therefore, during wetter climates, paleolakes and river networks around the Druze Marsh may have provided an additional inland route for hominins dispersing between Africa, Eurasia, and the Arabian Peninsula.  相似文献   

16.
The viscoelastic relaxation behaviour of lherzolite and marble and their temporal fractal properties are studied. Based on the high‐temperature viscoelastic behaviour for these rock types derived from the time–temperature superposition principle, the relaxation function for the viscoelastic behaviour of lherzolite and marble can be expressed as a flow law from a power‐law function of temperature‐reduced time given by normalizing the various temperature behaviours, with a non‐integer exponent. The relaxation function is thus time‐scale invariant, i.e. there is a temporal fractal property to the temperature‐reduced time. Their rheological behaviour over geological time‐scales at low temperature can be extrapolated from the experimental high‐temperature behaviour based on the temporal fractal property. Our derived flow law satisfies not only transient behaviour but also steady‐state behaviour.  相似文献   

17.
S. H. Ominde 《GeoJournal》1981,5(6):539-556
In recent years the population/development debate has shifted to consideration of the adequacy of resources to meet the accelerating population growth especially in developing countries. In the second area of concern the problem has been the adverse impact of the rate of population growth on availability of land.The history of Kenya's population growth clearly shows a steep rise from just after World War II to the late 1970s. In quantitative terms the rate of population growth has increased from just about 2% per annum to almost 4% per annum. The cause of the accelerated growth of population lies in the rising fertility and in particular to the sharp reduction in mortality and foetal loss as a result of development process.The rise in growth rate has taken place at different rates in accordance with limited areas of medium and low potential land. The implications of the spatial differential rates of growth include a significant decline in land availability and acceleration in the rate of soil loss. Equally more important is pressure on available water and wood fuel resources.In terms of policy options, Kenya must accommodate itself to continued acceleration of population growth and increasing pressure on land resources. The policy options include a rise of land in the main productive heartland of the country and water management policy that will permit an enlargement of agricultural land in the semi-arid and arid zones which constitute almost 2/3 of the land area. However, a permanent solution must rely in development of human resources and in the moderation of population growth.  相似文献   

18.
An investigation to characterize the extent and speciation of lead contamination in water, soil, and surrounding biota was conducted at a small-arms firing and skeet range in West Point, New York. Specifically, lead concentrations were examined in sediment, soil, water, plants, fish and invertebrates. There is an elevated concentration of lead in the soil and sediment up to 11,000 g/g and 340 g/g and also evidence of bioconcentration of the lead by the surrounding biota. Earthworms had up to 90% higher concentrations of lead while tadpoles showed 20% higher concentrations compared with their controls. Lead uptake by indigenous plants gave varying results. Two species bioconcentrated lead 20 and 55 times greater than the control plants. These differences were significant (P <0.05 level) when tested by the students t test. Further studies show that the total leachable lead was highest in the invertebrates and vertebrates but not in the plants.  相似文献   

19.
This article is designed to be used as the basis for a student exercise. Students compare statistics about two semiarid regions, one in Africa and one in North America. While cattle are an important part of the economies of both regions, cultural differences lead to different land use outcomes. Local differences in land use, in turn, lead to differing influences on global change.  相似文献   

20.
Pierpaolo Mudu 《GeoJournal》2002,58(2-3):189-196
The World Gay Pride week convened in Rome in July 2000 at the same time the Catholic Church planned on celebrating its Holy Year Jubilee. Thousands of gays came together, and by the end of the week more than 200,000 marched through the streets of Rome's historical centre. This unique event provides an opportunity to examine the causal relationship of the gay movement acquiring a political identity of its own while the city of Rome was trying to assert a `proper' identity for its public spaces. Acting in solidarity for the first time since its formation, the gay movement drew attention to the difficulties in securing unrestricted access to Rome's public spaces. Conservative sectors of society challenged the right to demonstrate, as guaranteed in Italy's Constitution, which resulted in the delay of obtaining the necessary permit. On the one hand, this revealed the existence of sectors of society not yet willing to acknowledge gay rights or even discuss gay issues in public; on the other, it helped make clear that the process for building Rome's identity is governed by a specific political design. In particular, policies for the privatisation of urban space in conjunction with discriminatory planning processes in the city's historical centre, point to tourism as a powerful tool to control urban space. Resisting this spatial marginalization the gay movement has significantly widened the scope of its social and political action in order to contest prevailing practices and trends which are shaping the city.  相似文献   

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