有向拓扑的河系渐变自动绘制算法     

吴伟  李成名  殷勇  郭沛沛 《测绘科学》2016,(12):89-93

河系渐变绘制是地图制图中水系要素表达的重要方面。针对全自动河系渐变研究较少的现状,该文提出一种基于树状约束stroke特征的河系渐变自动绘制算法。该方法在深入分析有向拓扑的数据结构基础上,重点解决河口模式识别、树状约束stroke特征构建、河系层次关系建立、主支流分级渐变等问题,实现全自动河系渐变,并进行实践测试。结果表明,该算法在地图制图过程中无须对河系河源、河口识别、河系分层和河系渐变进行人工干预,自动化程度高,大幅度提升制图效率,渐变效果优于人工绘制效果。  相似文献   

Estimating apparent thermal diffusivity of soil using field temperature time series     

Pathmanathan Rajeev  Jayantha Kodikara 《Geomechanics and Geoengineering》2016,11(1):28-46

Reliable estimates of soil thermal properties such as heat capacity, thermal conductivity, and diffusivity are important in analysis of heat transmission through soils in applications such as shallow geothermal applications, buried electrical conduits, and in general heat/fluid flow analyses. A number of analytical, numerical and experimental methods are available to determine the soil thermal properties. In this paper, the analytical and numerical methods developed on the basis of one-dimensional heat conduction equation are used to estimate the apparent thermal diffusivity of soil. Three of the four analytical methods, Amplitude, Phase, and Arctangent provide explicit equations for the apparent thermal diffusivity. Two methods, Harmonic and Numerical, make use of large number of temperature measurements to implicitly solve for the apparent thermal diffusivity. The temperature time series data monitored at different depths in two field sites in Melbourne, Australia for more than 2 year period were used to estimate the apparent thermal diffusivity of soil down to 2 m depth. The apparent thermal diffusivity was calculated using all five methods and compared with laboratory experimental results. The effectiveness of each method in predicting the thermal diffusivity was compared and observed discrepancies were discussed. Finally, the observed soil temperature data for a 12 month period are used to model the temperature variation in the ground analytically using Harmonic method and the model prediction for the following 12 month was compared independently with the field measurements. The analytical model prediction is found to be in good agreement with the field monitored data.  相似文献   

超微粉碎在孔石莼多糖提取中的应用   总被引：1，自引：1，他引：0  

綦慧敏  赵婷婷  张全斌  张虹  牛锡珍  赵增芹 《海洋科学》2005,29(12):56-58

研究超微粉碎技术在孔石莼（Ulva pertusa）多糖提取中的可行性。分别用超微粉碎后提取和常规提取两种方法提取孔石莼多糖,在不同条件下比较其提取率和所得产品的质量。结果表明,超微粉碎后的孔石莼在125℃提取4h收率达到17．39％,与常规方法比较其收率提高28．8％,主要化学组分及其含量没有差异,红外图谱也表明,两种方法所得的孔石莼多糖其主要官能团没有差异,说明超微粉碎技术在孔石莼多糖提取过程中的应用是可行的,它除了保持孔石莼多糖的品质外,可在较易控制的条件下提高其提取率。  相似文献   

单轴压缩下软岩的动态力学特性试验研究   总被引：7，自引：0，他引：7  

李海波  王建伟  李俊如  周青春  刘亚群 《岩土力学》2004,25(1):1-4

对软岩(砂浆模拟材料)进行了应变速率范围为10-5~101s-1的动单轴压缩实验。实验结果表明,试样的抗压强度随应变速率的增加有较明显的增加趋势,增加幅度大于硬岩;试样的弹性模量以及泊松比随着应变速率的增加均有增加的趋势,但幅度小于强度的增加幅度。并根据不同应变速率下试样破裂面的SEM实验结果,初步地分析了软岩动态力学特性机理。  相似文献   

黄上丘陵林地土壤侵蚀与土壤性质变化     

查小春  唐克丽 《地理学报(英文版)》2003,13(3):373-378

The serious soil erosion caused the fragile eco-environment in the Loess Plateau. In modern soil erosion of the Loess Plateau, the man-made accelerated erosion was the dominant erosion pattern (Tang etal., 1993a; 1993b). There are many kinds of human activities to accelerate erosion, of which the most influential activities are to destroy forest and grass, even to destroy vegetation. Reclamation at the expense of destruction of forestland and grassland artificially could increase soil erosio…  相似文献   

冬春季青藏高原北麓河多年冻土活动层中气体CO2浓度分布特征   总被引：14，自引：4，他引：10  

赵拥华  赵林  武天云  唐素然 《冰川冻土》2006,28(2):183-190

2005年1~5月在青藏高原北麓河附近的高寒干草原、高寒草甸和高寒草原3种典型草地上进行了不同深度土壤气体采样和CO₂浓度分析.结果表明:土壤剖面的土壤气体CO₂浓度呈现出上低下高的分布特征.在动态变化上,土壤中CO₂浓度在多年冻土活动层春季升温过程中出现一个峰值,经过短暂的降低后随夏季融化过程开始而升高.土壤剖面CO₂浓度与土壤有机碳、重组有机碳、轻组有机碳、水溶性有机碳、植物残体有机碳、微生物碳贮量和土壤温度呈明显的相关关系,在100 cm以上深度与土壤水分呈负相关关系.在整个观测期间,高寒干草原、高寒草原和高寒草甸植被下3种土壤剖面土壤气体CO₂浓度变化范围分别为1 052~3 050 mL·m^-3、3 425~39 144 mL·m^-3和984~12250 mL·m^-3,高于我国塿土CO₂浓度变化范围,也远远高于青藏高原五道梁地区高寒草原土壤气体CO₂浓度变化范围.石灰简育寒冻雏形土和石灰寒冻砂质新成土CO₂浓度变化范围低于国外报道的草地和农田CO₂浓度变化范围;石灰草毡寒冻雏形土CO₂浓度变化范围明显高于国外报道的草地和农田CO₂浓度变化范围.活动层冻结期,土壤CO₂的闭蓄作蓄作用比较明显.由于微地形导致土壤水分条件的差异,夏季融化过程各观测点土壤CO₂浓度开始升高时间存在差异.  相似文献   

不同荷载作用下拉破裂的声发射特征研究     

郭彦双  朱维申  李术才  林春金  温暖冬  杨磊 《岩土力学》2006,27(Z1):1055-1058

采用类岩石材料研究了不同加载条件下的张拉裂纹的破裂过程,并利用声发射(AE)测试技术分析了劈拉试样和三点弯曲试样在断裂过程中裂纹的萌生、起裂、扩展和破裂全过程的声发射特征。试验结果表明,声发射的阶段性突发特征反映了张拉裂纹阶段性扩展的力学机制。但是,在不同的加载条件下,张拉破裂的声发射特征有所差异：在弯拉应力作用下,试样拉破裂的声发射特征表现可分为声发射数的渐进增长、快速增长、突发式增长和逐渐下降4个阶段;而在劈拉应力作用下,试样破裂的声发射特征可分为声发射数缓慢增长、声发射数突发和声发射数的稳定发展3个阶段。在弯拉应力作用下,裂纹的萌生和聚集阶段的声发射特征明显,但在劈拉应力作用下几乎观察不到其声发射特征变化。不同破裂模式下的声发射特征值得进一步研究。  相似文献   

细粒含量对尾矿材料液化特性的影响   总被引：2，自引：0，他引：2  

张超  杨春和 《岩土力学》2006,27(7):1133-1137

为了模拟沉积分选后颗粒组成的变化对尾矿材料的动力特性的影响,尾矿筛分后按不同的细粒（颗粒直径小于 0.074 mm）含量制备尾矿试样,并进行了大量的土动力学试验。分析了细颗粒含量对尾矿材料的动力液化特性的影响规律。研究表明,对于铜矿类尾矿坝的尾矿材料,当细颗粒含量占到总量的35 %时其抗液化性能最佳。根据尾矿材料动力特性试验的研究结果,并结合现场的标准贯入试验成果,提出了适用于尾矿材料的细粒含量对标准贯入击数的修正式。该式可以分析不同细粒含量的尾矿材料的抗液化强度,提高尾矿坝液化判别方法的判别准确程度。  相似文献   

Estimating field‐saturated soil hydraulic conductivity by a simplified Beerkan infiltration experiment          下载免费PDF全文

V. Bagarello  S. Di Prima  M. Iovino  G. Provenzano 《水文研究》2014,28(3):1095-1103

Field‐saturated soil hydraulic conductivity, K_fs, is highly variable. Therefore, interpreting and simulating hydrological processes, such as rainfall excess generation, need a large number of K_fs data even at the plot scale. Simple and reasonably rapid experiments should be carried out in the field. In this investigation, a simple infiltration experiment with a ring inserted shortly into the soil and the estimation of the so‐called α* parameter allowed to obtain an approximate measurement of K_fs. The theoretical approach was tested with reference to 149 sampling points established on Burundian soils. The estimated K_fs with the value of first approximation of α* for most agricultural field soils (α* = 0.012 mm^?1) differed by a practically negligible maximum factor of two from the saturated conductivity obtained by the complete Beerkan Estimation of Soil Transfer parameters (BEST) procedure for soil hydraulic characterization. The measured infiltration curve contained the necessary information to obtain a site‐specific prediction of α*. The empirically derived α* relationship gave similar results for K_fs (mean = 0.085 mm s^?1; coefficient of variation (CV) = 71%) to those obtained with BEST (mean = 0.086 mm s^?1; CV = 67%), and it was also successfully tested with reference to a few Sicilian sampling points, since it yielded a mean and a CV of K_fs (0.0094 mm s^?1 and 102%, respectively) close to the values obtained with BEST (mean = 0.0092 mm s^?1; CV = 113%). The developed method appears attractive due to the extreme simplicity of the experiment. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Estimation of soil hydraulic properties and their uncertainty through the Beerkan infiltration experiment          下载免费PDF全文

Saeed Ghavidelfar  Asaad Y. Shamseldin  Bruce W. Melville 《水文研究》2015,29(17):3699-3713

The Beerkan method based on in situ single‐ring water infiltration experiments along with the relevant specific Beerkan estimation of soil transfer parameters (BEST) algorithm is attractive for simple soil hydraulic characterization. However, the BEST algorithm may lead to erroneous or null values for the saturated hydraulic conductivity and sorptivity especially when there are only few infiltration data points under the transient flow state, either for sandy soil or soils in wet conditions. This study developed an alternative algorithm for analysis of the Beerkan infiltration experiment referred to as BEST‐generalized likelihood uncertainty estimation (GLUE). The proposed method estimates the scale parameters of van Genuchten water retention and Brooks–Corey hydraulic conductivity functions through the GLUE methodology. The GLUE method is a Bayesian Monte Carlo parameter estimation technique that makes use of a likelihood function to measure the goodness‐of‐fit between modelled and observed data. The results showed that using a combination of three different likelihood measurements based on observed transient flow, steady‐state flow and experimental steady‐state infiltration rate made the BEST‐GLUE procedure capable of performing an efficient inverse analysis of Beerkan infiltration experiments. Therefore, it is more applicable for a wider range of soils with contrasting texture, structure, and initial and saturated water content. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献