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71.
A 132 kVA electrical transmission line has been proposed to connect the towns of Eket and Ikot Abasi in the eastern Niger delta in Nigeria. A geotechnical and hydrological study was performed to geotechnically characterize the route alignment and to provide data for design of the foundations for the transmission towers. In this paper, we introduce the study location and its geological, topographical and physiological characteristics, present the hydrological and geotechnical investigations and their results, and make recomendations for the design of the transmission tower foundations. Hydrological inspection of the power line alignment revealed that the route is traversed by numerous tributaries of the Qua-Iboe and Imo Rivers, the two major rivers that control the drainage of the study area. In-situ geotechnical tests consisted of cone penetration tests (CPTs), vane shear tests, test pit sampling (0–2.0 m depth) and lithologic boreholes (20 and 50 m deep). Laboratory tests included grain size analysis, pH determination and Atterberg Limits. Based on the CPT log pattern, no of stratum, and refusal depths, the soils along the transmission alignment were classified into twelve structural domains having common geotechnical properties. Because of the elevated water levels, and the nature of the soils, deep pile foundations were recommended for the towers. Software from the Louisiana Transportation Research Center, was employed to estimate skin friction, end bearing, and ultimate bearing capacities for assumed 225 mm square shaped reinforced concrete pile in each of the different zones of the alignment. 相似文献
72.
73.
Kinder A Sierts-Herrmann A Biselli S Heinzel N Hühnerfuss H Kammann U Reineke N Theobald N Steinhart H 《Marine environmental research》2007,63(5):506-515
Heat shock proteins 70 (hsp70) are known to be induced by a great variety of chemical stressors. The effects of different environmental contaminants, which were identified in sediments of the North Sea and the Baltic Sea as main contaminants or as contaminants of special toxicological interest, on the extent of expression of hsp70 in a permanent cell line Epithelioma papulosum cyprini (EPC) were investigated. Concentrations of the single contaminants leading to elevated hsp70 levels were compared to the respective concentrations of these contaminants encountered in the sediment extracts thus allowing an assessment of their contribution to the toxicity of these sediments. Analysis of hsp70 was performed using western blotting techniques with subsequent comparative quantification by densitometry. Eleven of thirteen contaminants have shown a dose-dependent increase in hsp70 levels. An expression of hsp70 was observed in most cases between 0.1 and 10 microg/mL test solution. Some of the investigated stressors led to extremely high hsp70 contents even at low concentrations. However, in most cases contaminant concentrations in sediments were too low to cause an effect. For this reason, effects of the tested sediments are attributed to other contaminants or rather to mixtures of stressors. 相似文献
74.
H. S. Jeon S. Cho Y. S. Kwak J. K. Chung J. U. Park D. K. Lee M. Kuzmicz-Cieslak 《Astrophysics and Space Science》2011,332(2):341-351
The atmospheric mass density of the upper atmosphere from the spherical Starlette satellite’s Precise Orbit Determination
is first derived with Satellite Laser Ranging measurements at 815 to 1115 km during strong solar and geomagnetic activities.
Starlette’s orbit is determined using the improved orbit determination techniques combining optimum parameters with a precise
empirical drag application to a gravity field. MSIS-86 and NRLMSISE-00 atmospheric density models are compared with the Starlette
drag-derived atmospheric density of the upper atmosphere. It is found that the variation in the Starlette’s drag coefficient
above 800 km corresponds well with the level of geomagnetic activity. This represents that the satellite orbit is mainly perturbed
by the Joule heating from geomagnetic activity at the upper atmosphere. This result concludes that MSIS empirical models strongly
underestimate the mass density of the upper atmosphere as compared to the Starlette drag-derived atmospheric density during
the geomagnetic storms. We suggest that the atmospheric density models should be analyzed with higher altitude acceleration
data for a better understanding of long-term solar and geomagnetic effects. 相似文献
75.
绿洲边缘夏季小气候特征及地表辐射与能量平衡特征分析 总被引:13,自引:15,他引:13
利用“绿洲系统能量与水分循环过程观测试验”加强期(IOP)在甘肃省酒泉市金塔绿洲观测的资料,分析了夏季金塔绿洲边缘的小气候特征及地表辐射收支和地表能量平衡特征。作为绿洲沙漠相互作用的界面,在白天绿洲边缘的垂直运动仍然是以上升气流为主,并且其小气候主要受土壤湿度的影响。中午前后绿洲边缘的总辐射最大值在1000W.m-2左右,净辐射>700W.m-2;在白天,仅有个别天数的感热通量超过100W.m-2,最大值仅为150W.m-2左右。在整个观测期,有超过70%的天数出现负感热通量。而Bowen比在±10-1量级,地表能量不平衡的差额较大,约28%。 相似文献
76.
N.BRATCHELL 《地理学报(英文版)》1989,(3)
Analysis of multivariate response data by modelling the principal components of the response has beenapplied to two sets of data. In both cases principal components analysis revealed the relationships amongthe response variables and exploited them to simplify the problem of modelling and optimizing themultivariate response. The models and optima obtained from the principal components comparedfavourably with the individual models and simultaneous optima. 相似文献
77.
78.
Following a general representation of the regression analysis, especially concerning the relations between flow and concentrations of matter and loads, these relations are represented and discussed for the suspended solids, nitrate concentration, chloride content and oxygen concentration for seven sections of the Spree river. There result clear connections to the structure and utilizations of all of the parts of the river basin. Finally, the covering of the total river basin by models of water quality management in the form of regression, self-purification and eutrophication models-and their coupling is represented. 相似文献
79.
The Burhi Dining river flows in a meandering course for about 220 km through alluvial plains of Assam including a short rocky and hilly tract in between. Sequential changes in the position of banklines of the river due to consistent bank erosion have been studied from Survey of India topographic maps of 1934 and 1972, and digital satellite data of 2001 and 2004 using GIS. Two broad kinds of changes have been observed, e.g. alteration of direction of flow due to neck cut-off and progressive gradual change of the meander bends that accounts for translational, lateral, rotational, extensional and other types of movement of the meander bends. Study of bankline shift due to the bank erosion has been carried out for the periods 1934–1972, 1972–2001, 2001–2004 and 1934–2004 at 13 segments spaced at 5′ longitude interval (average 15 km) as the river course trends nearly east to west. The amounts of the bank area lost due to erosion and gained due to sediment deposition are estimated separately. The total area eroded in both banks during 1934–1972 was more (26.796 km2) as compared to sediment deposition (19.273 km2), whereas total sediment deposition was more (34.61 km2) during 1972-2001 as compared to erosion (23.152 km2). Erosion was again more in 2001–2004 (7.568 km2) as compared to sediment deposition (2.493 km2). During the entire period (1934–2004) of study the overall erosion on the both banks was 31.169 km2 and overall sediment deposition was 30.101 km2. The highest annual rates of bank erosion as well as bank building of the river are 21055.47 m2/km in 2001–2004 and 9665.81 m2/km in 1972-2001, respectively. Similarly the highest average annual rates of erosion as well as sediment deposition in both banks are observed during 2001–2004 and 1972–2001, respectively. The hard rocks of the hilly tract situated in between result in development of entrenched meandering and this tract has suffered minimum bank erosion. 相似文献
80.
P. S. Harikumar Ph.D. U. P. Nasir M.Sc. M.Phil. in Chemistry M. P. Mujeebu Rahman M.Sc. in Chemistry 《International Journal of Environmental Science and Technology》2009,6(2):225-232
Five sediment cores from the fresh water region of the Vembanad wetland system were studied for the trace element contents The average concentration of iron, manganese, nickel, copper, zinc, cadmium, lead, mercury and chromium were determined. The core samples were collected using gravity type corer, digested with a mixture of nitric acid and perchloric acid and analyzed by atomic absorption spectrophotometry. Heavy metals such as iron, copper, nickel and zinc reported enrichment towards the surface of the core sediment sample collected from the centre of the lake. Lead, cadmium and mercury showed uniform distribution through out the core. Quality of the sediments were evaluated based on sediment quality guidelines, pollution load index, sum of toxic units and with effect range low/effect range median and threshold effect level/probable effect level values of Environmental Protection Agency guidelines. The degree of contamination for each station was determined. The concentration of different heavy metals has been compared with the world average concentration of shale values. Results of the analysis showed that Vembanad lake is facing serious metal pollution with increased rate of deposition. 相似文献