高速公路边坡稳定性评价新方法   总被引：3，自引：0，他引：3  

张菊连  沈明荣 《岩土力学》2011,32(12):3623-3629

为能在初期勘察阶段及少量室内和现场试验的基础上快速、准确地对高速公路边坡进行稳定性评价,提出了一种新的边坡稳定性评价方法。基于福建省高速公路边坡资料,以现场稳定情况为因变量,影响边坡稳定性的14个因子为自变量,利用Logistic逐步回归遴选显著影响因子,建立了边坡稳定性评价的Logistic回归模型。该模型符合拟合优度检验,模型稳定性良好,且预测结果准确。另外,模型影响因子的调查和获取比较容易,模型可处理定性因素,边坡稳定评价过程亦方便、快捷,因而边坡稳定性评价的Logistic回归分析可在高速公路边坡工程中推广应用。  相似文献   

基于Logistic回归模型的北京市水库湿地演变驱动力分析   总被引：8，自引：1，他引：7  

李洪  宫兆宁  赵文吉  宫辉力 《地理学报》2012,67(3):357-367

水库湿地作为北京市面积最大的人工湿地,是北京市重要的生态基础设施。从自然环境和社会经济因素两个方面,构建北京市水库湿地演变的驱动因子指标体系,其中自然驱动因子包括年均降水量、气温、入境水量和地下水埋深;社会经济驱动因子包括常住人口数、城市化率和人均GDP。应用长时间序列(1984-2010 年) 的TM遥感影像,提取北京市近30 年来水库湿地的空间分布信息,根据湿地面积增长和消退的演变规律,利用Logistic 回归模型定量分析不同时间段下水库湿地演变的驱动机制。结果表明:不同时期内水库湿地变化的驱动因子及其影响力存在一定的差异。在1984-1998 年间,北京市水库湿地增长变化的主导驱动因子是年均降水量和入境水量,Logistic 回归的贡献率分别为5.778 和3.504,主要受自然环境因素的影响;在1998-2004 年期间,水库湿地急剧减少的驱动因子主要为常住人口、地下水埋深和城市化率,影响贡献率分别为9.41、9.18 和7.77,人为活动的影响开始加剧;在2004-2010 年间,影响水库湿地发生变化的主导因子是城市化率和年均降水量,贡献率分别为6.62 和4.22,受自然和社会经济因素的交叉影响。  相似文献   

Reconstructing changes in macrophyte cover in lakes across the northeastern United States based on sedimentary diatom assemblages     

Jesse C. Vermaire  Irene Gregory-Eaves 《Journal of Paleolimnology》2008,39(4):477-490

Macrophytes are a critical component of lake ecosystems affecting nutrient and contaminant cycling, food web structure, and lake biodiversity. The long-term (decades to centuries) dynamics of macrophyte cover are, however, poorly understood and no quantitative estimates exist for pre-industrial (pre-1850) macrophyte cover in northeastern North America. Using a 215 lake dataset, we tested if surface sediment diatom assemblages significantly differed among lakes that have sparse (<10% cover; group 1), moderate (10–40% cover; group 2) or extensive (>40% cover; group 3) macrophyte cover. Analysis of similarity indicated that the diatom assemblages of these a priori groups of macrophyte cover were significantly different from one another (i.e., difference between: groups 1 and 3, R statistic = 0.31, P < 0.001; groups 1 and 2, R statistic = 0.049, P < 0.01; groups 3 and 2, R statistic = 0.112, P < 0.001). We then developed an inference model for macrophyte cover from lakes classified as sparse or extensive cover (145 lakes) based on the surface sediment diatom assemblages, and applied this model using the top-bottom paleolimnological approach (i.e., comparison of recent sediments to pre-disturbance sediments). We used the second axis of our correspondence analysis, which significantly divided sparse and extensive macrophyte cover sites, as the independent variable in a logistic regression to predict macrophyte cover as either sparse or extensive. Cross validation, using 48 randomly chosen sites that were excluded from model development, indicated that our model accurately predicts macrophyte cover 79% of the time (r ² = 0.32, P < 0.001). When applied to the top and bottom sediment samples, our model predicted that 12.5% of natural lakes and 22.4% of reservoirs in the dataset have undergone a ≥30% change in macrophyte cover. For the sites with an inferred change in macrophyte cover, the majority of natural lakes (64.3%) increased in cover, while the majority of reservoirs (87.5%) decreased in macrophyte cover. This study demonstrates that surface sediment diatom assemblages from profundal zones differ in lakes based on their macrophyte cover and that diatoms are useful indicators for quantitatively reconstructing changes in macrophyte cover.  相似文献   

旅游目的地形象与目的地感知吸引力关系——以厦门市为例     

郭安禧  孙雪飞  王纯阳 《热带地理》2015,35(6):943-949

为明确目的地形象的细分维度与目的地感知吸引力的关系,以厦门市为例,基于问卷调查,利用Logistic回归模型实证研究认知形象、情感形象、总体形象对目的地感知吸引力的影响。结果表明：1）目的地品牌、自然和文化2个认知形象因子对目的地感知吸引力有显著正向影响,休闲娱乐和接待环境2个认知形象因子对目的地感知吸引力没有显著正向影响;2）情感形象、总体形象对目的地感知吸引力皆有显著正向影响;3）情感形象对目的地感知吸引力的影响大于认知形象对目的地感知吸引力的影响。  相似文献   

Identifying transit corridors for elephant using a long time-series     

Claudia Pittiglio  Andrew K. SkidmoreHein A.M.J. van Gils  Herbert H.T. Prins 《International Journal of Applied Earth Observation and Geoinformation》2012,14(1):61-72

The role of corridors in mitigating the effects of landscape fragmentation on biodiversity is controversial. Recent studies have highlighted the need for new approaches in corridor design using long-term datasets. We present a method to identify transit corridors for elephant at a population scale over a large area and an extended period of time using long-term aerial surveys. We investigated environmental and anthropogenic factors directly and indirectly related to the wet versus dry season distribution of elephant and its transit corridors. Four environmental variables predicted the presence of elephant at the landscape scale in both seasons: distance from permanent water, protected areas and settlements and vegetation structure. Path analysis revealed that altitude and monthly average NDVI, and distance from temporary water had a significant indirect effect on elephant distribution at local scale in dry and wet seasons respectively. Five transit corridors connecting Tarangire National Park and the northern as well as south-eastern wet season dispersal areas were identified and matched the wildlife migration routes described in the 1960s. The corridors are stable over the decades, providing landscape connectivity for elephant. Our approach yielded insights how advanced spatial analysis can be integrated with biological data available from long-term datasets to identify actual transit corridors and predictors of species distribution.  相似文献   

Well site conditions associated with nitrate contamination in a multilayer semiconfined aquifer of Buenos Aires,Argentina     

L. I. Carbó  M. C. Flores  M. A. Herrero 《Environmental Geology》2009,57(7):1489-1500

A stepwise logistic regression (LR) model was generated to evaluate the association between contamination of groundwater by nitrates with several risk factors such as soil types, farm facilities and practises, and well characteristics. The odds ratio was calculated to estimate the degree of impact that the associated variables had on the risk of contamination in a semiconfined multilayer aquifer underlying rural areas of Buenos Aires, Argentina. Duplicate farm groundwater samples (n = 160) were taken and nitrate was analyzed. Data, involving various farm factors, was gathered via two questionnaires concerning farm’s general and productive aspects, and well characteristics. Statistical tests were run between nitrates and each variable present in the survey. A 96.25% of the samples presented detectable nitrate levels, 40.91% of which had more than 45 ppm nitrates. The final LR model involved five of the variables under study: well age, soil permeability, depth of water table, location, and distance from well to contamination sources. Cross validation proved to be a good estimator of nitrate water contamination. Suspicions about how these characteristics influence groundwater contamination by nitrates were confirmed, and as these five factors represent a higher risk for this type of aquifer, their proper management may contribute to a better resource protection.  相似文献   

基于Logistic模型及水驱曲线的一种综合预测模型   总被引：1，自引：0，他引：1  

孙来喜  付国民  冯文光  石京平 《矿物岩石》2002,22(4):97-100

水驱曲线法与开发模型法是油藏工程的重要预测方法，但二者孝有一定的缺陷。将广泛适用的Logistic峰型模型和甲型、丙型水驱曲线相结合，建立一种综合预测模型，这种模型不但可以预测某一特定时间水驱油田的产油量、累积产油量、含水率、水驱波及系数，而且可以预测水驱油田的可采储量、可动油储量和最终水驱波及系数。  相似文献   

Landslide susceptibility mapping: A comparison of logistic regression and neural networks methods in a medium scale study, Hendek region (Turkey)   总被引：36，自引：0，他引：36  

E. Yesilnacar  T. Topal   《Engineering Geology》2005,79(3-4):251-266

Landslide susceptibility mapping is one of the most critical issues in Turkey. At present, geotechnical models appear to be useful only in areas of limited extent, because it is difficult to collect geotechnical data with appropriate resolution over larger regions. In addition, many of the physical variables that are necessary for running these models are not usually available, and their acquisition is often very costly. Conversely, statistical approaches are currently pursued to assess landslide hazard over large regions. However, these approaches cannot effectively model complicated landslide hazard problems, since there is a non-linear relationship between nature-based problems and their triggering factors. Most of the statistical methods are distribution-based and cannot handle multisource data that are commonly collected from nature. In this respect, logistic regression and neural networks provide the potential to overcome drawbacks and to satisfy more rigorous landslide susceptibility mapping requirements. In the Hendek region of Turkey, a segment of natural gas pipeline was damaged due to landslide. Re-routing of the pipeline is planned but it requires preparation of landslide susceptibility map. For this purpose, logistic regression analysis and neural networks are applied to prepare landslide susceptibility map of the problematic segment of the pipeline. At the end, comparative analysis is conducted on the strengths and weaknesses of both techniques. Based on the higher percentages of landslide bodies predicted in very high and high landslide susceptibility zones, and compatibility between field observations and the important factors obtained in the analyses, the result found by neural network is more realistic.  相似文献   

Assessment of sidewall erosion in large gullies using multi-temporal DEMs and logistic regression analysis   总被引：3，自引：0，他引：3  

J. A. Martínez-Casasnovas  M. C. Ramos  J. Poesen 《Geomorphology》2004,58(1-4):305-321

Although in the last decades gully erosion has been a thriving research field, few studies have specifically addressed the contribution and location of sidewall erosion processes in gullies. In this paper, sidewall erosion in some large gullies in a Mediterranean area (Anoia-Penedès, NE Spain) is mapped and assessed for two time intervals (1975–1995 and 1995–2002), using detailed digital elevation models derived from aerial photographs at a scale of 1:5000 to 1:7000. Logistic regression analysis is applied to compute the probability of occurrence of gully sidewall erosion from terrain variables. The results confirm the complex nature of sidewall processes, whose intensity is most probably related to rainfall characteristics. Prolonged wet soil conditions in the period 1995–2002, together with the large and high-intensity rainfall of an extreme event occurred on 10th June 2000, help to explain the different sediment production rates: 16±0.4 Mg ha⁻¹ year⁻¹ in 1975–1995 and 83±6.3 Mg ha⁻¹ year⁻¹ in 1995–2002. The logistic regression analysis revealed that gully-wall slope angle was the main factor controlling gully sidewall failure. In gully walls with high slope angles, tension crack development is the main process promoting wall collapse. The application of the logistic regression model showed a high overall accuracy (87%) but over 50% of commission and omission errors for the class of interest (sidewall erosion), in agreement with the variance explained by the model.  相似文献   

基于Logistic回归及前期有效雨量的降雨诱发型滑坡预测方法   总被引：17，自引：0，他引：17  

李铁锋  丛威青 《中国地质灾害与防治学报》2006,17(1):33-35

滑坡预测预报一直是国内外滑坡灾害研究的重点。且多数滑坡均属降雨诱发型。为此将降雨诱发型滑坡的研究列为重中之重。但是,降雨与滑坡发生的关系不仅密切,而且非常复杂。除降雨外,还涉及到地质、气象、水文、土壤等多个学科。因此,至今尚未总结出一种对降雨诱发型滑坡进行定量预测预报的成熟方法。文章将Logistic回归模型与前期有效降雨量结合,形成一套对降雨诱发型滑坡进行定量预测预报的方法。并以长江三峡地区为例进行了检验,效果较好。  相似文献