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81.
"Diurnal population change in subareas of metropolitan regions is of increasing importance to urban geographers...and planners.... The urban context of daytime populations is that of commuting. Commuting, in turn, has been investigated almost exclusively within the setting of empirical economic research.... The purpose of the present study is to continue some recent attempts to find an alternative to the empirical economic approach to commuting, in advancing a formal demographic and spatial concept of diurnal population cycle." Data from the 1991 census of Canada are used. (EXCERPT)  相似文献   
82.
Concentrations of 222Rn were measured in ancient copper mines which exploited the Faynan Orefield in the South-Western Jordanian Desert. The concentrations of radon gas detected indicate that the ancient metal workers would have been exposed to a significant health risk and indicate that any future attempt to exploit the copper ores must deal with the hazard identified. Seasonal variations in radon concentrations are noted and these are linked to the ventilation of the mines. These modern data are used to explore the differential exposure to radon and the health of ancient mining communities.  相似文献   
83.
We have studied the process of a prolonged dynamic filtration on activated carbon in two biosorption systems — without preoxidation treatment of the initial matter and after ozonization. It has been shown that given the uniform load on activated carbon terms of the organic matter the efficiency of the biosorption process after preozonization is 2.3 times as small compared with that that without pretreatment, which correlates with the change of adsorption free energy.  相似文献   
84.
A finite element method which is applicable to studying the distortional buckling of fabricated monosymmetric I-beams is briefly described. The method is used to demonstrate the effects of web slenderness on a monosymmetric I-beam whose smaller flange is in compression. A study is also made of the effects of monosymmetry on the distortional buckling of an I-beam with a slender web in uniform moment and moment gradient. Based on parameter studies using the finite element method, a design equation is developed which may be used to determine the distortional buckling stress of a monosymmetric I-beam under moment gradient.  相似文献   
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Journal of Electroceramics - CuO nanocrystal (NC) films of different grain sizes were synthesized through the oxidation of Cu films deposited by controlling the supersaturation in the deposition...  相似文献   
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Russian Electrical Engineering - In this paper, we ground a method for calculating switching overvoltages including the discharge of lightning currents into the contact network and into a...  相似文献   
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Russian Electrical Engineering - This paper presents the results of a study of the effect of the characteristics of the traction power-supply system on the indicator of the energy supply of...  相似文献   
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