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121.
Early results from the 2001 census of England allow a preliminary analysis of joblessness. People in the prime working ages (25–49) are more likely to be in work than those in their 50s, but the differences are quite subtle: in particular, men without qualifications are not much more likely to be in work when they are younger, despite the suggestions that too many men cease working in their 50s. The evidence supports the view that there is a national shortfall of demand for labour, that the low-skilled are the least able to compete for scarce jobs, and older people are the most likely to be unqualified. Moreover there is a strong spatial clustering of areas where job availability has declined or grown least, undermining the government's claim that there were often available jobs near to concentrations of people without work. 相似文献
122.
Yohannes Aberra 《The Geographical journal》2004,170(3):226-237
The Mekele Plateau, located in the semi-arid northern highland region of Ethiopia, is a drought-prone, highly degraded area. It has long been neglected by policymakers and thus recurring famine, widespread poverty, armed conflicts and mass outmigration have contributed to the near collapse of the farming systems and the livelihoods of the population. Traditional stream diversion irrigation has been practised in this area for several centuries. The systems of water management in particular may be considered inappropriate owing to the need for thriftiness in water use imposed by the local environment. The systems of headworks and canals are crude and wasteful on water. Recent interventions to improve the small-scale irrigation systems of the area have not been successful. Most interventions have preferred to introduce rainwater harvesting systems using micro-dams rather than trying to upgrade the traditional diversion schemes. Evaluation of irrigation structures in the field, interviews with key informants in government, analysis of documents and discussions with irrigators indicate that both the Ministry of Agriculture and SAERT-Commission's rainwater harvesting programmes have generally failed. The case of the most recent intervention by SAERT has failed because of myopic project planning, inadequate engineering studies, unsound designs, too short a time for implementation, and lack of full farmer involvement at different levels of project planning and implementation. 相似文献
123.
F. Gutirrez 《Geomorphology》2004,57(3-4):423-435
The salt valleys over the axis of the salt-cored anticlines in the Paradox fold and fault belt (Canyonlands, Utah and Colorado) are created by subsidence of the anticline crests. Traditionally, the collapse of the anticlinal crests was attributed to dissolution of the salt walls (diapirs) forming the anticline cores. Recent studies based on scaled physical models and field observations propose that the salt valleys are a result of regional extension and that salt dissolution had only a minor influence in the development of the axial depressions. This paper presents several arguments and lines of evidence that refute the tectonic model and support the salt dissolution subsidence interpretation.The development of contractional structures in salt dissolution experiments led the advocates of the tectonic interpretation to reject the dissolution-induced subsidence explanation. However, these salt dissolution models do not reproduce the karstification of salt walls in a realistic way, since their analog involves removal of salt from the base of the diapirs during the experiments. Additionally, numerous field examples and laboratory models conducted by other authors indicate that brittle subsidence in karst settings is commonly controlled by subvertical gravity faults.Field evidence against the regional extension model includes (1) a thick cap rock at the top of the salt walls, (2) the concentration of subsidence deformation structures along the crest of the anticlines (salt walls), (3) deformational structures not consistent with the proposed NNE extension, like crestal synforms and NE–SW grabens, (4) dissolution-induced subsidence structures controlled by ring faulting, revealing deep-seated dissolution, (5) large blocks foundered several hundred meters into the salt wall, (6) evidence of recent and active dissolution subsidence, and (7) the aseismic nature of the recently active collapse faults. Although underground salt dissolution seems to be the main cause for the generation of the salt valleys, this phenomenon may have been favored by regional extension tectonics that enhance the circulation of groundwater and salt dissolution. 相似文献
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125.
A procedure is proposed for the reconfiguration of the macroseismic planes relative to earthquakes that, being characterized by a reduced number of points of observed intensity due to a lack of information, or having the epicenter very close to the coastline, are characterized by an incomplete distribution of observed intensity levels. The design of a plurality of virtual areas, through which a distribution of intensity consistent with an anisotropic model of attenuation is depicted, allows a reliable determination of macroseismic parameters of the same seismic event. 相似文献
126.
High buildings or architectural complex in urban areas remarkably distort the urban surface wind fields. As the air flow approaches,local strong wind may appear around the buildings. The strong wind makes the pedestrians on sidewalks, entrances and terrace very uncomfortable and causes the pedestrian level wind environment problem. In this studies, hot-wire wind measurement, wind scouring in wind tunnel and numerical computation were carried out to evaluate the wind environment of tall buildings in the prevailing flow conditions in Beijing areas. The results obtained by three techniques were compared and mutually verified. The conclusions drawn from three approaches agree with each other. Also the advantages and limitations of each method were analyzed. It is suggested that the combination of different techniques may produce better assessment of wind environment around high buildings. 相似文献
127.
Based on the land surface temperature (LST), the land cover classification map,vegetation coverage, and surface evapotranspiration derived from EOS-MODIS satellite data, and by the use of GIS spatial analytic technique and multivariate statistical analysis method, the urban heat island (UHI) spatial distribution of the diurnal and seasonal variabilities and its driving forces are studied in Beijing city and surrounding areas in 2001. The relationships among UHI distribution and landcover categories, topographic factor, vegetation greenness, and surface evapotranspiration are analyzed. The results indicate that: (i) The significant UHI occur in Beijing city areas in the four seasons due to high heat capacity and multi-reflection of compression building, as well as with special topographic features of its three sides surrounded by mountains,especially in the summer. The UHI spatial distribution is corresponding with the urban geometry structure profile. The LST difference is approximately 4-6℃ between Beijing city and suburb areas, comparatively is 8- 10℃ between Beijing city area and outer suburb area in northwestern regions. (ii) The UHI distribution and intensity in daytime are different from nighttime in Beijing city area, the nighttime UHI is obvious. However, in the daytime, the significant UHI mainly appears in the summer, the autumn takes second place, and the UHI in the winter and the spring seem not obvious. The surface evapotranspiration in suburb areas is larger than that in urban areas in the summer, and high latent heat exchange is evident, which leads to LST difference between city area and suburb area. (iii) The reflection of surface landcover categories is sensitive to the UHI, the correlation between vegetation greenness and UHI shows obviously negative.The scatterplot shows that there is the negative correlation between NDVI and LST (R2 = 0.6481).The results demonstrate that the vegetation greenness is an important factor for reducing the UHI,and large-scale construction of greenbelts can considerably reduce the UHI effect. 相似文献
128.
Uur Doan 《Geomorphology》2005,71(3-4):389-401
Karstification-based land subsidence was found in the Upper Tigris Basin with dimensions not seen anywhere else in Turkey. The area of land subsidence, where there are secondary and tertiary subsidence developments, reaches 140 km2. Subsidence depth ranges between 40 and 70 m. The subsidence was formed as a result of subsurface gypsum dissolution in Lower Miocene formation. Although there are limestones together with gypsum and Eocene limestone below them in the area, a subsidence with such a large area is indicative of karstification in the gypsum. The stratigraphical cross-sections taken from the wells and the water analyses also verify this fact. The Lower Miocene gypsum, which shows confined aquifer features, was completely dissolved by the aggressive waters injected from the top and discharged through by Zellek Fault. This resulted in the development of subsidence and formation of caprock dolines on loosely textured Upper Miocene–Pliocene cover formations. The Tigris River runs through the subsidence area between Batman and Bismil. There are four terrace levels as T1 (40 m), T2 (30 m), T3 (10 m) and T4 (4–5 m) in the Tigris River valley. It was also found that there were some movements of the levels of the terraces in the valley by subsidence. The subsidence developed gradually throughout the Quaternary; however no terrace was formed purely because of subsidence. 相似文献
129.
130.