研究气温变化趋势的新方法——三组耐抗线     

刘俊卿  杨军  强德厚 《干旱气象》2007,25(1):79-82

针对气象资料难以满足高斯分布的情况,引进了具有耐抗性的三组耐抗线方法,分析了满足不同信度情况下最小二乘回归和三组耐抗线的差异,并用西藏近30 a气温资料进行了检验。结果表明三组耐抗线方法比最小二乘法研究气候变化趋势有明显优势;采用最小二乘法得到的西藏气候变暖估计偏高。  相似文献   

Computational fluid dynamics modeling of abutment scour under steady current using the level set method     

《国际泥沙研究》2020,35(4):355-364

The scour and deposition pattern around an abutment under constant discharge condition is calculated using a three dimensional (3D) Computational Fluid Dynamics (CFD) model. The Reynolds-Averaged Navier Stokes (RANS) equations are solved in three dimensions using a CFD model. The Level Set Method (LSM) is used for calculation of both free surface and bed topography. The two-equation turbulence model (k-ε and k-ω) is used to calculate the eddy viscosity in the RANS equations. The pressure term in the RANS equations on a staggered grid is modeled using the Chorin's projection method. The 5th order Weighted Essentially Non-Oscillatory (WENO) scheme discretizes the convective term of the RANS equations. The Kovacs and Parker and Dey formulations are used for the reduction in bed shear stress on the sloping bed. The model also used the sandslide algorithm which limits bed shear stress reduction during the erosion process. The numerical model solution is validated against experimental results collected at the Politecnico di Milano, Milan, Italy. Further, the numerical model is tested for performance by varying the grid sizes and key parameters like the space and time discretization schemes. The effect of varying bed porosity has been evaluated. Overall, the free surface is well represented in a realistic manner and bed topography is well predicted using the Level Set Method (LSM).  相似文献   

孔隙尺度多孔介质流体流动与溶质运移高性能模拟          下载免费PDF全文

周鸿翔  郑延丰  吴劳生  陈铖  曾令藻 《水科学进展》2020,31(3):422-432

深入探究孔隙尺度下的流体流动特性和溶质运移规律对石油开采、农田养分管理、地下水污染修复有着重要意义。以人工构建的多孔介质结构和同步辐射X射线显微CT扫描的土壤团聚体(分辨率3.7μm)为研究对象,在空间节点数多达64 000 000的情况下,基于格子Boltzmann模型和GPU并行技术计算得到多孔介质流体运动和溶质运移过程的关键参数,并据此探究多孔介质空间异质性对水力学特性的影响。通过对3组不同结构的多孔介质比较发现,结构复杂程度最高的土壤样品和不规则堆叠的圆球结构的渗透率在100 mD(即10^-13m^2)量级,远低于规则堆叠的圆球结构(>20 000 mD);土壤的迂曲度为1.40~1.60,明显高于规则堆叠的圆球结构。研究结果表明,渗透率大的样品具有较小的迂曲度,这与结构的空间异质性有较强的关系;土壤的渗透率和迂曲度呈现各向异性;在水力梯度一定的前提下,渗透率较大的样品,纵向弥散系数也较大;同时,结构的异质性也会影响溶质的穿透曲线。本研究提出的模拟方法可在土壤结构中进行高效的水流运动和溶质运移模拟,可用于土壤多孔介质在孔隙尺度下的水力学特性研究。  相似文献   

脆弱生态环境定量评价方法的研究   总被引：132，自引：4，他引：128  

赵跃龙 《地理科学》1998,18(1):73-79

建立了一套系统、完整、客观、灵活且具较强可操作性的脆弱生态环境定量评价指标体系及方法,并通过用此法评价全国２６个省、区生态环境脆弱度的方式,对其可操作性和准确性进行了验证。  相似文献   

一种利用贝叶斯最小判别准则估计未来地震危险的新方法   总被引：2，自引：0，他引：2  

金学申  邵辉成 《中国地震》1998,14(3):88-93

提出了一种基于最大似然和贝叶斯最小判别准则的新预测方法,它的长处在于对样本数无特殊要求,所以,对低地震活动地区,此模型也能得到与时间有关的稳定的未来强震危险估计。最后,以华北地区为例,说明了本方法的可行性。  相似文献   

Shallow landslides in deeply weathered slates of the Sierra de Collcerola (Catalonian Coastal Range, Spain)     

Domenico Calcaterra  Jos A. Gili  Roberto Iovinelli 《Engineering Geology》1998,50(3-4):283-298

Stability conditions in an area located NW of Barcelona (Spain) are discussed. Here, several mass movements were observed, mainly affecting weathered Paleozoic slates. Many of these failures involved slopes cut along recent infrastructures: debris flows, wedge and plane failures, generally surficial, occurred more frequently. After a detailed geological and geomorphologic survey, geomechanic characterization was carried out, according to RMR and SMR classifications. This rating gave a prediction of slope behaviour, in fairly good agreement with the real observed one.

Stability numerical analysis was carried out for the main cut slopes, based upon the Limit Equilibrium Method. First of all, the deterministic factor of safety was computed using the mean values of parameters. After that, a simulation technique based upon the Monte Carlo Method was applied in order to obtain factor of safety distributions. The probability of failure was estimated as P(F<1).

Finally, results from deterministic and probabilistic approaches were compared. The effectiveness of different possible remedial measures was highlighted by means of a sensitivity analysis, which showed that the more important parameters in the study area are the geometrical ones (height, slope and failure plane angles). The final technical solutions adopted are briefly outlined.  相似文献   

逆斜率法及其讨论     

吴耀华 《上海国土资源》1998,(1):29-34,45

经对上海地区51根试桩资料分析表明,同实测值比较,计算值误差一般不超过30％,误差与未次加载的ΔSn/ΔPn比值似有一定的相关性,当比值大于2,误差一般不超过20％,同时对没有达到终至加载条件的试桩也可采用此法估算。  相似文献   

位移时空综合分析法及其在边坡工程中的应用   总被引：1，自引：1，他引：0  

尚彦军  唐纯华 《工程地质学报》1998,6(3):238-243

以往对监测位移数据分析方法主要是位移-时间关系分析。但监测数据包含了大量对工程设计和施工都很有用的信息,其中不乏位移-空间方面的信息;另一方面,从工程设计和施工角度看,除需要位移-时间信息外,还需要位移-空间信息。位移时空综合分析法的提出旨在综合位移-时间和位移-空间等两方面的信息,为工程设计和施工服务。该方法依表现形式不同又分为竖线法和曲面法两种。本文将通过五强溪船闸边坡工程实例,来进一步说明位移时空综合分析法的原理及其应用。  相似文献   

The generation and redistribution of overland flow on a massive oxic soil in a eucalypt woodland within the semi-arid tropics of North Australia     

Mike Bonell  John Williams 《水文研究》1986,1(1):31-46

There is a dearth of knowledge on the runoff processes of eucalypt woodland communities in the semi-arid tropics of Australia. The work was undertaken on a 100 m transect of a 0·8 degree hillslope typical of the ‘smooth plainlands’ of central-north Queensland. This paper introduces a new experimental design for measuring overland flow in such areas by way of a cascade system of unbounded runoff plots which allow the inputs and outputs between troughs to be calculated. Most storms generate overland flow. Time to overland flow ranges between 1 and 18 min where rain intensities are above 10mm hr⁻¹ and when the average detention storage of 3·6 mm is exceeded. The bare soil surfaces within the scattered grass understory control the runoff generation process through the temporal variability of field saturated hydraulic conductivity. The study demonstrated that overland flow is mainly redistributed over the freely-draining oxic soil. Some areas export more overland flow than they gain from upslope (runoff), others gain more overland flow than they export (runon). Over the study period only 2 per cent of total rain is transferred out of this 100 m transect as overland flow due to the short duration of storms, the relatively high soil permeability, and the low slope angle. The remainder adds to the large soil water store or deep drainage. The variability of runoff–runon over these ‘smooth plainlands’ highlights how results from bounded plots would be misleading in such areas.  相似文献   

水产养殖遥感监测及信息自动提取方法研究   总被引：2，自引：0，他引：2  

关学彬  张翠萍  蒋菊生  曹建华 《国土资源遥感》2009,(2):41-44

以海南省文昌地区为例,在沿海地区尝试利用遥感监测的手段提取水产养殖地块和面积.采用面向对象的分类方法进行监测,取得了理想效果,同时也提出了提高分类精度的建议.  相似文献