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991.
采用实验室模拟的方法,研究海洋环境对掺复合镍铁渣粉水泥土强度的影响。本文将镍铁渣粉和矿粉混合后,作为掺和料掺入到水泥土中。通过海洋环境侵蚀分析、无侧限抗压强度试验、SEM和EDS试验分析,研究了海洋环境对复合镍铁渣粉水泥土的表观特征、强度性能及微观形貌的影响。试验结果表明:海洋环境对水泥土的表观结构具有侵蚀作用,同时对其强度也具有劣化作用,而且随着侵蚀时间的增加海洋环境对其侵蚀劣化作用越来越强;水泥土中掺入的复合镍铁渣粉能发挥出微集料效应和活性效应,因而具有良好的耐久性。复合镍铁渣粉不仅能提升水泥土的强度,同时能降低海洋环境对其表观结构的侵蚀,缓解海洋环境对其强度的劣化作用。 相似文献
992.
Atmospheric particulate matter (PM) fractions (PM(10) and PM(2.5)) were sampled concurrently between June 2004 and May 2005 at two sites (urban and suburban) in Izmir, Turkey. The elemental composition of PM (Al, Ba, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Sr, V, and Zn) was determined using inductively coupled plasma-optical emission spectrometer. Elemental compositions of several PM sources were also characterized. Positive matrix factorization (PMF) and chemical mass balance modeling (CMB) were applied to determine the PM sources and their contributions to air concentrations. The major contributors to PM were fossil fuel burning, traffic emissions, mineral industries and marine salt according to the PMF results. However, undetermined parts were more than 40%. On the other hand, the contributions to PM could be determined completely by CMB, and the dominant contributor was traffic with >70% at the two sites. Fossil fuel burning, mineral industries, marine salt and natural gas-fired power plant were the minor contributors. 相似文献
993.
Ljung K Torin A Smirk M Maley F Cook A Weinstein P 《The Science of the total environment》2008,407(1):589-593
Air quality is commonly assessed by the ambient concentration of airborne particles sized smaller than 10 microm (PM10). However, in addition to concentration, particle shape as well as the type and bioaccessibility of elements adsorbed to this particulate fraction are likely to be related to subsequent respiratory health effects. In order to investigate this relationship, a relatively large mass of the relevant size fraction is needed since sample preparation is necessary prior to analysis. Most existing methods for sampling dust have been developed for analysing the dust directly, without prior handling or digestion. In order to provide sufficient material to be used for subsequent bioaccessibility analysis, these methods require repetitive and time consuming sampling as well as special equipment and procedures which are high in both cost and maintenance. This paper describes an inexpensive and relatively simple procedure for extracting the PM10 fraction from soil to be used for lung bioaccessibility studies. The method described involves dry and wet sieving in order to exclude larger size fractions as far as possible. Vacuum filtering of the wet-sieved soil solution through a 10 microm mesh was then employed to extract the required fraction. In order to avoid frequent blocking of the mesh, Stokes's law was applied in the construction of a tube which enables separation of the solution holding the smallest fraction. 相似文献
994.
Pérez N Pey J Castillo S Viana M Alastuey A Querol X 《The Science of the total environment》2008,407(1):527-540
Results on interpretation of the variability of regional background PM levels in the Western Mediterranean basin (WMB) are presented. Mean PM levels recorded at Montseny, MSY (North-Eastern Spain) in the 2002-2007 period reached 17, 13 and 11 µg/m3 of PM10, PM2.5 and PM1, respectively.The daily evolution of PM levels is regulated by the breeze circulation (mountain and sea breezes). PM levels are lower at the rural sites at night owing to the nocturnal drainage flows and to the lowering of the mixing layer height below the MSY high. These nocturnal low levels allowed us to estimate the continental background PM levels. At midday, the atmospheric pollutants accumulated in the pre-coastal depression are transported upwards by the breeze, increasing PM levels.Maximum PM10 levels were recorded in summer, and February-March and November, and minimum values in the rest of the year coinciding with the highest frequency of Atlantic advection. PM peak episodes attributed to Saharan dust outbreaks were recorded in summer and February-March. In addition, anticyclonic situations (February-March and November) may impact in elevated rural areas by increasing hourly levels of PM1 up to 75 µg/m3. This scenario induces the stagnation of pollutants in the pre-coastal depression. Solar radiation activates mountain winds, transporting polluted air masses from the valleys to elevated areas resulting in an increase of fine PM levels in areas outside the boundary layer.A significant decrease in PM annual means (40% and 34% for the entire monitoring period, 7 µgPM10/m3 and 5 µgPM2.5/m3) was recorded at MSY between 2002 and 2007. There appears to be no single cause behind these trends. This could partially be ascribed to the varying frequency and intensity of Saharan dust episodes, but also to large-scale meteorological processes or cycles, and/or to local or meso-scale processes such as nearby anthropogenic emission sources. 相似文献
995.
Spatial competition and regulatory change in the grain handling and transportation system in western Canada 总被引:2,自引:0,他引:2
The grain handling and transportation system (GHTS) has been a defining component of the western Canadian economy since the
early part of the last century. Only two major railways serve the grain handling industry, so the potential for the exercise
of market power in transportation appears to be significant. In fact, spatially oriented regulations applicable to railways
exist in Canada to mitigate this, but to date they have not often been used by shippers. While the reasons for this are not
completely clear, we suggest that the regulations are now inadequate for the current state of the GHTS. Using a unique data
set from the year 2000, we assess the effect on the grain handling industry of modifications to these regulations, and find
that significant gains for shippers from these modifications are possible. These gains are computed to be on the order of
C$10–15 million per year for grain shippers alone.
We would like to thank conference and presentation participants (Transportation Research Board, Canadian Agricultural Economics
Society, University of British Columbia, University of Leeds and California State University, Long Beach) as well as the anonymous
reviewers who commented on the earlier versions of this paper. We would also like to acknowledge support from the Saskatchewan
Department of Highways. 相似文献
996.
The use of activity-based modeling to analyze the effect of land-use policies on travel behavior 总被引:1,自引:1,他引:0
Yoram Shiftan 《The Annals of Regional Science》2008,42(1):79-97
This paper suggests that in order to analyze the effect of land-use policies on travel behavior an integrated framework that
extend travel activity-based models to include various land-use issues such as residential location and work place should
be developed and use. The importance of analyzing various land-use policies on travel behavior is continuously increasing
as various policies such as transit-oriented developments, mixed land-use, different concentrations schemes, and more broadly
Smart Growth, are often suggested as a means to mitigate transportation problems. Given our limited understanding of the effects
of the various land-use polices on travel behavior it is imported to develop better approaches to analyze such policies. Activity-based
models, that treat travel as a derivation of the demand for personal activities, provides an opportunity to better understand
travel behavior as the explicit modeling of activities and the consequent tours and trips enable a more credible analysis
of responses to policies and their effect on traffic and air quality. The theoretical framework of activity-based models starts
with urban and land-use development as inputs; however, there is a need to translate this framework to analyze specific land-use
policies. This paper discusses the advantages and potential of activity-based models for analyzing the effect of land-use
policies on travel behavior. It suggests improvements that will extend the general framework to achieve a better understanding
of travelers’ responses to various land-use policies and shows its advantages over tip-based models, which simply do not have
such capabilities. The improved activity-based approach is illustrated through a case study based on the Portland activity-based
model combined with a stated-preference residential choice model. A package of land-use policies— including improved land-use,
school quality, safety, and transit service in the city center—is introduced, and its effect on household redistribution and
regional travel is tested using this integrated framework. The results of this case study show that the effects of the land-use
policies introduced had only marginal effects on regional travel. 相似文献
997.
Geographically and technologically mediated knowledge spillovers between European regions 总被引:8,自引:1,他引:8
This paper aims at investigating inter-regional knowledge spillovers across European sub-national regions. The basic questions that we wish to answer may be formulated in the following way: do regional geographical and technological proximities matter for the creation of new knowledge within the European regional landscape? After a review of the related literature, we consider a regional knowledge production function that allows for extra regional innovation-generating inputs. Accounting for regional specific social capability, this knowledge production function is applied to an extended sample of 153 European sub-national regions over the period 1989–1996. Interregional knowledge spillovers are shown to exist between geographically close regions and between regions displaying similar technological profiles. However, technological proximity and geographical proximity coincides to a certain extent. Knowledge spillovers are mainly driven by the private business sector. If knowledge spillovers occur within a given country, the national border turns out to seriously hamper interregional spillovers on the European scale.
The author wishes to thank Eckhardt Bode, Henri Capron, Raymond J.G.M. Florax, Charlie Karlsson, Roger Stough and Roger Vickerman for their useful comments and suggestions. An earlier version of this paper was presented at the 41st Annual Meeting of the Western Regional Science Association in February 2002, Monterey, California. 相似文献
998.
利用扫描电镜(SEM)、X-射线衍射(XRD)以及傅立叶红外光谱(FTIR)技术研究改性聚丙烯酰胺(MPAm)对其改性超细水泥复合材料水化的影响。结果表明,由于聚合物与水化物之间的强烈的相互作用,改性聚丙烯酰胺大大影响了水泥的正常水化程度,但却改善了水化产物的微观结构,有助于提高水泥的韧性以及其他性能如抗折强度。 相似文献
999.
1000.
Kirkpantur A Kahraman S Genctoy G Altun B Abali G Arici M Turgan C 《Hemodialysis international. International Symposium on Home Hemodialysis》2008,12(3):352-361
Interleukin-10 (IL-10) predominantly acts as an anti-inflammatory factor. Polymorphisms in the IL-10 gene promoter determine quantitative cytokine production. Doppler echocardiography and tissue Doppler imaging (TDI) are superior to conventional echocardiography to evaluate diastolic dysfunction. The IL-10 gene promoter polymorphism at position (-1082) was studied for its association with conventional and Doppler echocardiographic and TDI parameters in 112 hemodialysis (HD) patients. Blood pressure, serum C-reactive protein (CRP), and albumin levels were also examined for the association study. The genetic association study showed that among the HD patients, there was no difference in the prevalence of systolic and diastolic dysfunction between genotypes on conventional echocardiography. However, using Doppler echocardiography and TDI, high producers for the IL-10 -1082 promoter (-1082/GG) have higher E velocities, E/A values, lateral, and septal E' velocities and a lower isovolumic ventricular relaxation time than low (-1082/AA) and intermediate producers (-1082/GA). Significantly higher levels of serum CRP levels and lower plasma albumin levels were found in low and intermediate producers for the IL-10 -1082 promoter than high producers. The IL-10 genotype may balance the effects of inflammatory cytokines on the myocardium and may be a determinant of LV function in HD patients. 相似文献