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381.
基于FLAC3D有限差分软件对开挖深度、侧压力系数、断面形状等多因素影响下的巷道变形参数进行正交试验,根据正交试验分析结果,分别选取同一深度条件下的圆形、马蹄形、直墙拱形、矩形巷道进行模拟试验并以圆形巷道作为典型断面,对不同深度下的巷道变形特征进行模拟试验。研究结果表明:开挖深度对巷道开挖后的应力差变化影响明显,断面形状对巷道围岩内的塑性区深度和具有显著影响;巷道开挖后的塑性区深度和随形状指数增加而呈线性增长趋势,圆形巷道的塑性区深度和最小,矩形最大;应力差随着巷道开挖深度的增加呈线性增加,深部开采应重视巷道内的应力分布情况。 相似文献
382.
The biomarker approach has been used for 25 years to study the environmental quality of marine, brackish and freshwater ecosystems. Biomarkers may indicate health status and can be applied to organisms of all zoological phyla by destructive or non destructive methods. For 5 years we have been using this approach in zooplankton to detect ecotoxicological alterations at low levels of the food chain due to contaminants. Here we review our approach to validate and apply biomarker techniques in zooplankton. We discuss advantages, limitations, some results and future research. We indicate that biomarkers in zooplankton can be used as new indices of trophic status and ecological integrity of Italian marine coastal and lagoon environments, to be included among the tools specified by Italian law D.Lgs. 152/2006. 相似文献
383.
本文在简要讨论了海岸带及其资源可持续开发利用的基础上,提出了海岸带管理的整合模式──系统综合管理模式。并详细分析了海岸带系统综合管理模式的内容和方法。 相似文献
384.
基于新经济地理学相关理论,针对江苏省沿江开发战略实施以后,制造业空间可能存在的变动,在整理和分析调查问卷资料的基础上,选择专业化指数和基尼系数2种方法来定量分析江苏省21个沿江省级以上开发区空间分工、制造业集聚和转移态势。结果表明:(1)2002~2006年江南沿江开发区通过向江北沿江开发区转移部分传统产业,逐渐形成了江南沿江技术/资本密集型制造业“中心”和江北沿江劳动密集型制造业“外围”的空间分工格局;(2)江南沿江开发区内部、江北沿江开发区内部尚未形成良好的分工关系;(3)受开发区发展阶段、区域产业政策、本地化资源供给和市场需求等因素影响,并未发现理论预期的普遍存在的产业集聚现象,仅纺织服装、石化、电力、塑料橡胶等产业呈现集中趋势. 相似文献
385.
以盘塘红壤实验区为例,在阐明湘北环湖低丘红壤区土壤形成、类型及特性的基础上,提出了综合开发利用该区土壤资源的措施和途径。 相似文献
386.
The spatial and temporal variability of transparency measured for 15 years at 7 stations near the San Diego sewage outfall has been investigated and compared to the temporal variability of sewage suspended solid discharge and flow rate. the purpose of the time-series analyses was to distinguish natural from human (sewage discharge) causes of temporal changes in transparency. the results show that: 1) variations in transparency are highly correlated over the entire area, but there is a gradient in means and variability in the direction perpendicular to the coast; 2) there are no long term trends for increase or decrease in the water clarity at any of the stations; 3) most of the variance of transparency is contained in the seasonal frequency band; 4) over the same time period sewage discharge has significantly increased and suspended solids decreased; 5) most of the variance of these human-caused properties is in the interannual frequency band; (6) there is no correlation at any time-lag between water clarity and suspended solid discharge or flow. These results lead to the conclusion that these anthropogenic properties are not affecting transparency, while natural factors such as seasonality and distance from coast do. 相似文献
387.
Lam K.C. 《中国人口.资源与环境(英文版)》2004,2(2)
The paper demonstrates why it is necessary to take the restoration of marine coastal ecosystem health as a new goal for integrated catchment management, in coastal area of the Tolo Harbour. The present goal of integrated catchment management (ICM) in the Tolo Harbour is to meet with Water Quality Objectives. The performance of an ICM plan, Tolo Harbour Action Plan (THAP), is evaluated by using marine coastal ecosystem health indicators including stress indicators and responses indicators. Since the implementation of THAP in 1988, some significant reduction in pollution loading has been observed - reduction of 83 % of BOD load and 82 % of TN between 1988 and 1999. There has been an improvement in the health state of Tolo Harbour marine coastal ecosystem as evidenced in the trends of the physical, chemical and biological indicators, although some reverse fluctuations in some periods exist. However, this can only be considered as the first sign of the ecosystem health restoration, since ecosystem health co 相似文献
388.
Forrest E. Dierberg 《Environmental management》1992,16(3):371-380
Following a period of prolonged drought or intentional lake level drawdown, large littoral areas that once contained submersed
aquatic vegetation (SAV) are reinundated when lake levels rise. A complete assessment of the contribution made by decomposing
SAV to the in-lake phosphorus (P) concentration is important in both the management of Lake Okeechobee and understanding basic
P processes. The P contribution to the open waters of Lake Okeechobee from a rapid inundation of exposed SAV was calculated
by four methods: cores of field-desiccated SAV, cores of lab-desiccated SAV in the presence and absence of sediments, in situ
decomposition, and sequential macrophyte harvesting. P releases, given such an episodic event, were similar among the four
methods, ranging from 116±48 to 384±528 mg/m2 in the absence of sediment. When SAV is in contact with sediment, which is the realistic field situation, the amount of P
released was four times less (30±14 mg/m2) than in the absence of sediment. The calculated P releases would result in total P concentration increases in the lake from
2 to 15 μg/liter (upper 95% CI=2–25 μg/liter) in the absence of sediment; only 1 μg/liter increase was predicted when SAV
released P in contact with sediment. Thus it is unlikely that a significant rise in total P concentrations in the limnetic
zone of the lake would occur from the export of P released during the desiccation of SAV in the littoral-marsh zone during
a drawdown. 相似文献
389.
F. Douglas Shields 《Journal of the American Water Resources Association》1991,27(3):527-536
ABSTRACT: Stability of vegetated and bare riprap revetments along a Sacramento River reach during the flood of record was assessed. Revetment damages resulting from the flood were identified using records provided by the U.S. Army Corps of Engineers and verified by contacts with local interests. Vegetation on revetments along a 35.6-mile reach was mapped using inspection records and stereo interpretation of aerial phoths taken shortly before and after the flood. A follow-up field inspection was conducted in September 1989. Revetment age, material, bank curvature, vegetation, and damage were mapped from a boat. Mapping results from both 1986 and 1989 were placed in a data base. About 70 percent of the bank line of the study reach was revetted. About two-thirds of the revetment was cobble; one-third was quarry stone. Revetment vegetation varied from none to large (> 50-inch diameter) cotton-woods. About 10 percent of the revetted bank line supported some type of woody vegetation. Damage rates for revetments supporting woody vegetation tended to be lower than for unvegetated revetments of the same age located on banks of similar curvature. Chisquared tests indicated damage rates were greater for older (pre-1950 construction) revetments, but were unable to detect differences based on vegetation or bank curvature. Research is needed to generate design criteria and construction techniques to allow routine use of woody plants in bank protection structures. 相似文献
390.
The threat of man-induced global change on the nations of the South Asian seas region varies from place to place because of
differences in exposure to monsoons and stoms, differences in local tectonics and subsidence, and variations in air and sea
climates. Because several nations are involved, some having subsistence budgets, and given the cost of deriving independently
a comprehensive response to global change, the similarities and differences between national settings must be identified soon.
These comparisons will form the basis for local response strategies: the similarities provide a basis for responses similar
to that of other nations and the differences provide for local adaptation. That climate change on the South Asian coastal
region will have an impact is certain: its economics, environment, and coastal land uses are dominated to a certain extent
by this marine influence. The extent of these impacts, however, is uncertain. Accompanying global change will be changes in
sea level, differences in storm climate, and altered precipitation patterns; science cannot define today what pattern these
changes will take. Because global change is inevitable—although its magnitude, timing, and geographic distribution are unknown—the
South Asian seas region should begin the appropriate research and planning studies to set forth a reasoned response to global
change, for implementation when scientific evidence for global change is more quantitative. 相似文献