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251.
从水泥土的固化机理出发,结合水泥搅拌桩桩身标准贯入试验和水泥土配合比试验,分析讨论了土性指标、土质条件和地层性质对水泥搅拌桩成桩质量的影响。 相似文献
252.
Partitioning,bioavailability and origin of heavy metals from the Nador Lagoon sediments (Morocco) as a basis for their management 总被引:2,自引:0,他引:2
Nador Lagoon sediments show low trace element concentrations, and, in relation to the lagoon geochemical baseline, only some
anomalies for As, Cd, Cu and Pb in the NW of the lagoon deserve to be outstanding. The distribution of major, minor and trace
elements in the lagoon allows a breakdown in four zones. Between “Beni Ensar” and “Atelouane” (zone A), a quite confined zone
rich in organic matter and S, the most important trace-element anomalies (As, Cd, Co, Cu, Mn, Pb, Zn) were found, mainly around
industry and old mining activities. In the surrounding of the city of Nador (zone B), the anomalies correspond to Mn, Cu and
Zn. The coastal barrier and Kebdana channel (zone C) show moderately concentrations of Cd, Cr and Ni at specific sites. The
less polluted area is the SE of the lagoon (zone D), with no outstanding anomaly. In lagoon sediments, metal bioavailability
is very low. The metal partitioning patterns show that Cu, Pb and Zn present a low availability because they are bounded to
the residual, non-mobile phases of the sediments. Only in some sites, the fraction was associated with organic matter, which
could be liberated easily. Arsenic is concentrated in both the residual phases and the organic matter, the latter being more
available. Cadmium is mainly concentrated in some samples in the interchangeable fraction, which could be considered as a
potentially toxic element because it is easily released. Concerning the origin of these trace elements, those found in zone A
correspond mostly to a natural source by weathering of mount Gourougou volcanic rocks (As, Co, Cu, Pb and Zn), and to an anthropogenic
origin (Cd) owing to the presence of industry and old mines. In zone B, contributions of Cu and Zn enter the lagoon through
soil weathering and river-borne, and as anthropogenic pollution from urban wastes. In zone C the most important pollutant
is Cd deduced to be of anthropogenic origin from the close industry and intensive agriculture area. In spite of the intense
socio-economic activities developed in the Nador Lagoon (agriculture, industry, fishing, tourism) trace element concentrations
in the sediments are low and with scarce bioavailability. Only the NW sector is relativity polluted because of geogenic features. 相似文献
253.
在总结大量实际工作的基础上,就区域生态环境遥感监测的指标与分类系统问题进行了探讨,提出了尽可能与现有的土地利用分类衔接,又较容易进行遥感判读和分类的土地利用分类系统;根据目前国内遥感数据获取和使用情况提出了遥感影像选择、处理以及合成的最佳方案,推荐了通过目视判读和自动分类获得土地利用状况的方法等,以期生态环境遥感监测能真正纳入环保部门常规的监测工作中. 相似文献
254.
255.
J. Venkata Ratnam D. R. Sikka Akshara Kaginalkar Amit Kesarkar N. Jyothi Sudipta Banerjee 《Pure and Applied Geophysics》2007,164(8-9):1641-1665
As a part of the Experimental Extended Range Monsoon Prediction Experiment, ensemble mode seasonal runs for the monsoon season
of 2005 were made using the National Centre for Environmental Prediction (NCEP), T170L42 AGCM. The seasonal runs were made
using six initial atmospheric conditions based on the NCEP operational analysis and with forecast monthly sea-surface temperature
(SST) of the NCEP Coupled forecast system (CFS). These simulations were carried out on the PARAM Padma supercomputer of Centre
for Development of Advanced Computing (C-DAC), India. The model climatology was prepared by integrating the model for ten
years using climatological SST as the lower boundary. The climatology of the model compares well with the observed, in terms
of the spatial distribution of rainfall over the Indian land mass. The model-simulated rainfall compares well with the Tropical
Rainfall Measuring Mission (TRMM) estimates for the 2005 monsoon season. Compared to the model climatology (7.81 mm/day),
the model had simulated a normal rainfall (7.75 mm/day) for the year 2005 which is in agreement with the observations (99%
of long-term mean). However, the model could not capture the observed increase in September rainfall from that of a low value
in August 2005. The circulation patterns simulated by the model are also comparable to the observed patterns. The ensemble
mean onset is found to be nearer to the observed onset date within one pentad. 相似文献
256.
A seismic design procedure that does not take into account the maximum and cumulative plastic deformation demands that a structure is likely to undergo during severe ground motion could lead to unsatisfactory performance. In spite of this, current design procedures do not take into account explicitly the effect of low‐cycle fatigue. Based on the high correlation that exists between the strength reduction factor and the energy demand in earthquake‐resistant structures, simple procedures can be formulated to estimate the cumulative plastic deformation demands for design purposes. Several issues should be addressed during the use of plastic energy within a practical performance‐based seismic design methodology. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
257.
南京城区夏季低层逆温对人体舒适状况影响初探 总被引:4,自引:2,他引:4
利用2000年夏季南京志区地面气象要素和低层探空资料,分析了该夏季南京城区早、晚低层逆温的频率、厚度和强度变化特征,着重从统计角度研究了逆温的厚度、强度与城区地面温度、相对湿度变化的关系及对人体舒适状况的影响。结果表明:低层逆温对城区地面温湿变化及其幅度影响较大,当07时有逆温层时,08时至14时的温度增加幅度变大,相对温度减小幅度也变大,人体不适指数增加幅度变大;当19时有逆温层时,20时至23时温度减小幅度变小,相对湿度增加幅度也变小,人体不适指数减小幅度变小,并通过相关分析建立了人体舒适度指数与逆温强度之间的回归方程。 相似文献
258.
海温变化对台风路径的影响 总被引:8,自引:2,他引:8
在台风模式中采用周平均海温和多年的月平均海温,对一些台风个例进行了比较,分析了数值模式中影响台风路径的海温因子变化对台风移动路径的影响。 相似文献
259.
Oracle Spatial 在GIS中的应用 总被引:8,自引:0,他引:8
本文介绍了Oracle数据库系统中对空间数据存储的解决方案,并针对对象关系模式下空间数据的存储和管理,结合自己的实际工作体会提出了一些具体的解决方法。 相似文献
260.
中国陆地生态系统脆弱带遥感模型 总被引:4,自引:0,他引:4
本研究通过对我国陆地生态系统8个典型样地的植被指数取样实验和图像计算结果发现,这8个样地植被指数随着水、热因子的季节变化,在时间和空间上具有一定的“绿波推移”和“景观更替”规律。在中国东部湿润的季风区(样地1-3),随着纬度的增高,其月平均植被指数与月平均气温有较大的相关。发现降水相对丰沛的地带,热量和光照条件的变化成为植被生长和变化的自然限制因子;而在中国北方森林-森林草原-典型昌原-荒漠草原-荒漠地带上,随着从东部(湿润地区)到西部(干旱地区)干湿条件的更替,月平均植被指数与降水多寡有较大的正相关关系。在8个样地上都呈现出共同的规律,即定向风的分布与植被指数的分布在时间和空间上具有逆相分布的“套合关系”。尤其在时间上有相逆套合关系,这正是中国北方沙尘暴和沙漠化加剧的自然原因。本研究定量地给出了我国陆地不同经纬度带生态系统脆弱季节和累积时间的分布。 相似文献