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Khraif RM 《GeoJournal》1992,26(3):363-370
"The aim of this paper is to investigate the factors affecting intentions of rural-migrants to return to their rural origins. Several socioeconomic, demographic, spatial, and temporal variables will be introduced to explore their explanatory power and interrelationship with the migrants' intentions. These variables are: Years lived in Riyadh, the current place of parents' residency, land ownership in the village, home ownership in the urban area, income, household size, and the area of origin. The data, which come from a sample survey of migrants conducted in Riyadh in 1983, will be analyzed by the means of binary logit model." 相似文献
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Although the degree of metal contamination is expected to be a primary determinant of metallothionein (MT) induction in marine mussels, at least at polluted sites, variability caused by temperature, and biotic factors such as size, may need to be considered when interpreting field data. To test the effects of these variables, mussels, Mytilus galloprovincialis, of different sizes (small: 3.5 +/- 0.5 cm and large: 5.2 +/- 0.7 cm) were exposed to Cd (100 microg l(-1)) at different water temperatures (5, 18 and 25 degrees C) for 34 days. Resultant Cd and MT concentrations in gills were shown to be size dependent and increased significantly with temperature. At the highest temperature tested (25 degrees C) there appears to be a disproportionate effect on Cd accumulation, which raises MT synthesis to exceptionally high levels. The effect of size on MT concentrations was also temperature-dependent: at 18 and 25 degrees C, large mussels exhibited higher MT levels than smaller individuals, whilst at 5 degrees C there were no significant differences between contaminated and control mussels, in either size-group, as a result of the reduced level of MT production at this temperature. When considering the use of MT levels in mussels as a biochemical indicator of metal contamination, the potential influence of factors such as size and temperature on MT-metal relationships needs to be considered. Samples should be of uniform size as far as possible, and collection should be limited to a fixed season (avoiding climatic extremes) to ensure that the effects of these factors on baseline levels of MT is minimised. 相似文献
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Ahsan RM 《International journal of population geography : IJPG》1997,3(1):49-61
The author analyzes migration patterns and processes of female construction workers in Dhaka City, Bangladesh, and considers the impact of this migration. "Interviews...reveal that the major goal of these female migrants, whose mobility and employment have traditionally been restricted, is to take responsibility in the struggle for livelihood.... Success of many migrations is linked with participation in construction work in the city. Employment in such activities is largely by women from male-headed households, indicating male support in the work, followed by females heading their own households." 相似文献
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作者设计了一种经济的软拷贝形式的摄影测量系统，该系统是为调查汽车碰撞而研制的。最初，该系统是以软片为基础的，使用由两个非量测摄影机构成的立体摄影机摄取影像，用一台幻灯投影器和一平板式数字化仪相组织，将像点坐标数字化。在所设计的数字化系统中，仍然采用立体摄影取影像，软片经摄影处理后，利用台式扫描仪获得影像的“软”拷贝。有了数字影像，就可以进行若干程度不同的自动化处理。此种软拷贝的摄影测量系统不再需要 相似文献
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数字摄像机和影像获取器的价格不断降低，加上其分辨率较高，结果是使用此类摄影机的摄影测量应用场合愈来愈多。原因是其在影像获取和影像量测的速度及自动化方面具有优势。本文中使用了标准帧转换电荷耦合器件摄影机来获近近影景数字影响，以用于像片三角测量，将该方法确定标志点三维坐标的精度与传统的三角测量方法的精度进行了比较，借助计算机的监视器，按交互方式利用了两种影像处理技术（影像相关和瞬间存贮）来测量标志点。 相似文献
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