长江三角洲末次盛冰期的气候波动   总被引：2，自引：0，他引：2  

覃军干  吴国瑄  郑洪波  周琪 《海洋地质与第四纪地质》2007,27(6):71-75

通过对长江三角洲东部地区鹤鸣孔第一硬黏土层的孢粉、藻类分析,研究了该地区末次盛冰期的气候波动。结果表明,鹤鸣孔第一硬黏土层含种类较丰富的孢子、花粉和藻类化石,并可以划分为3个孢粉、藻类组合,代表了该地区末次盛冰期气候变化的3个阶段,反映了该地区末次盛冰期并不是一个持续的干冷状况,第一硬黏土层沉积的早期和晚期气候较温暖湿润,针阔叶混交林发育,而中期阶段气候偏冷,植被贫乏。  相似文献   

Mapping Paleo‐Fire Boundaries from Binary Point Data: Comparing Interpolation Methods     

Amy Hessl  Jennifer Miller  James Kernan  David Keenum  Don McKenzie 《The Professional geographer》2007,59(1):87-104

Fire history studies have traditionally emphasized temporal rather than spatial properties of paleo‐fire regimes. In this study we compare four methods of mapping paleo‐fires in central Washington from binary point data: indicator kriging, inverse distance weighting, Thiessen polygons, and an expert approach. We evaluate the results of each mapping method using a test (validation) dataset and receiver operating characteristic plots. Interpolation methods perform well, but results vary with fire size and spatial pattern of points. Though all methods involve some subjectivity, automated interpolation methods perform well, are replicable, and can be applied across varying landscapes.  相似文献   

昌化鸡血石常见地子的成分与岩性     

李平  周越刚 《上海国土资源》2007,(3):59-62

从临安昌化镇和大峡谷镇采集了一百多个昌化鸡血石样品,分别对其作了岩石薄片鉴定、红外分析、X射线衍射分析,归纳总结了常见鸡血石种类的成分和岩性:冻地主要成分为地开石/高岭石,岩性为粘土质岩石;软地主要成分为强粘土化火山碎屑或粘土,岩性多为强粘土化凝灰岩-粘土质岩石;软刚地主要成分为蚀变火山碎屑/明矾石,岩性多为明矾石岩或中等粘土化/明矾石化凝灰岩;硬刚地主要成分为石英,岩性为弱明矾石化/弱粘土化凝灰岩;硬地主要成分为石英,岩性为弱-强硅化凝灰岩。  相似文献   

    

A. G. Journel 《Mathematical Geology》1986,18(3):269-286

Traditional interpolation algorithms, including krigings, do not account for inequality-type data less subjective qualitative information. Soft kriging formalism allows a coding of both hard data and constraint intervals as prior cumulative distribution functions (cdfs) which are interpolated into posterior cdfs. Non-Gaussian confidence intervals and various optimal estimates then are derived. A synthetic case study is presented.  相似文献   

Dynamic simulation for tempo-spatial distribution of strain energy density in inhomogeneous stratified crust     

陈宇坤  聂永安 《地震学报(英文版)》2000,13(6):636-645

IntroductionRupturetheorybasedonenergyconceptdisplaysthatstrainenergyanditsvariationinrockistheinvestigationrelevanttothebehaviorofrockdeformationandfracture.Itisoneofthemostimportantcriteriatodeterminethefractureposition,rupturingcondition,fracturedirectionaswellasrupturingscale.Therefore,toresearchonenergyfieldsofstrongearthquakes(focushasgreattheoreticalsignificancebothinunderstandingtheenergystateanditsvariationinthefocalarea,andincarryingoutexplicitpredictionforthetime,thelocationandthema…  相似文献   

砟子煤矿区硬质高岭(土)岩生产高白度煅烧高岭土工艺研究   总被引：1，自引：0，他引：1  

康震野 《吉林地质》2000,19(4):63-70

吉林省地质矿信息中心与白山市八道江区煤管局合作,对山地区石炭、二叠系煤系地层中的硬质高岭（土）岩进行了实验室加工试验,得出了影响砟子煤矿区硬质高岭（土）岩煅烧高岭土白度的六大因素,指出了煅烧工艺对砟子煤矿区硬质高岭（土）岩的关键所在,但各因素之间又是相关连,相互渗透的,对下一步建厂生产指明了方向,清楚地论述了应用砟子煤矿区硬质高岭（土）岩的煅烧加工过程,获得超细双９０型造纸涂料级产品的把握所在,双９０型产品指的是：粒度－２μｍ〉９０％,白度（ＧＥ高度）〉９０度。  相似文献   

高地应力下硬岩的本构模型研究   总被引：1，自引：0，他引：1  

陈景涛  冯夏庭 《岩土力学》2007,28(11):2271-2278

传统的本构模型在模拟高地应力下硬岩破坏的范围和深度方面并不理想。针对高应力下的拉西瓦花岗岩,通过真三轴压缩试验模拟了开挖时应力路径的演化。在摩尔-库仑强度准则、格里菲斯强度准则、德鲁克-普拉格准则、双剪统一强度理论和霍克-布朗强度准则的基础上,考虑十二面单元体主剪面上主剪应力、正应力和静水压力的共同作用,提出了一个有关高应力下硬岩的三剪强度准则。根据试验结果,利用遗传算法全局寻优的功能,搜索出了三剪强度准则的参数。预测样本和与摩尔-库仑强度准则、德鲁克-普拉格准则、双剪统一强度理论的比较表明,该三剪强度准则与试验结果吻合,适用于高地应力下的硬岩。根据试验得到的应力-应变关系曲线,建立了基于三剪强度准则和应变软化的弹-脆-塑性本构模型,并用FLAC3D提供的基于C++的用户自定义模型工具UDM,创建了用户自定义模型的动态链接库,嵌入了FLAC3D软件。采用遗传算法-FLAC方法,搜索得到了基于岩石试样和岩体的本构模型参数。计算结果与实测情况吻合,表明建立的本构模型适用于高地应力下的硬岩,为高地应力下硬岩地下工程的安全性和稳定性分析奠定了基础。  相似文献   

土壤侵蚀预报研究中的标准小区问题论证   总被引：19，自引：2，他引：17  

张科利  刘宝元  蔡永明 《地理研究》2000,19(3):297-302

确定标准小区在土壤侵蚀预报中具有重要意义,也是进行土壤侵蚀规律研究的必要基础。文中根据我国的自然环境条件、土壤侵蚀特征、农业生产特点,通过分析土壤侵蚀发生的地形特点、已有资料的坡度变化范围,以及土壤流失量估算中的误差变化规律,提出并论证了我国土壤侵蚀研究中的标准小区应选定15°坡度、20m坡长、5m宽的清耕休闲地。小区每年按传统方法准备成苗床,并按当地农作习惯适时中耕,保证没有明显的杂草生长。  相似文献   

Are spatial patterns of soil moisture at plot scales generalisable across catchments,climates, and other characteristics? A synthesis of synoptic soil moisture across the Mid-Atlantic     

Charles I. Scaife  Jonathan M. Duncan  Laurence Lin  Christina Tague  Colin D. Bell  Lawrence Band 《水文研究》2021,35(9):e14313

The spatial variation of soil moisture over very small areas (<100 m²) can have nonlinear impacts on cycling and flux rates resulting in bias if it is not considered, but measuring this variation is difficult over extensive temporal and spatial scales. Most studies examining spatial variation of soil moisture were conducted at hillslope (0.01 km²) to multi-catchment spatial scales (1000 km²). They found the greatest variation at mid wetness levels and the smallest variation at wet and dry wetness levels forming a concave down relationship. There is growing evidence that concave down relationships formed between spatial variation of soil moisture and average soil moisture are consistent across spatial scales spanning several orders of magnitude, but more research is needed at very small, plot scales (<100 m²). The goal of this study was to characterise spatial variation in shallow soil moisture at the plot scale by relating the mean of measurements collected in a plot to the standard deviation (SD). We combined data from a previous study with thousands of new soil moisture measurements from 212 plots in eight catchments distributed across the US Mid-Atlantic Region to (1) test for a generalisable mean–SD relationship at plot scales, (2) characterise how landcover, land use, season, and hillslope position contribute to differences in mean–SD relationships, and (3) use these generalised mean–SD relationships to quantify their impacts on catchment scale nitrification and denitrification potential. Our study found that 98% of all measurements formed a generalised mean–SD relationship like those observed at hillslope and catchment spatial scales. The remaining 2% of data comprised a mean–SD relationship with greater spatial variation that originated from two riparian plots reported in a previous study. Incorporating the generalised mean–SD relationship into estimates of nitrification and denitrification potential revealed strong bias that was even greater when incorporating mean–SD observations from the two riparian plots with significantly greater spatial variation.  相似文献   

Supporting USLE‐MM reliability by analyzing soil loss measurement errors          下载免费PDF全文

Vincenzo Bagarello  Vito Ferro 《水文研究》2017,31(4):847-853

Sampling the collected suspension in a storage tank is a common procedure to obtain soil loss data. A calibration curve of the tank has to be used to obtain actual concentration values from those measured by sampling. However, literature suggests that using a tank calibration curve was not a common procedure in the past. For the clay soil of the Sparacia (Italy) experimental station, this investigation aimed to establish a link between the relative performances of the USLE‐M and USLE‐MM models, usable to predict plot soil loss at the event temporal scale, and soil loss measurement errors. Using all available soil loss data, lower soil loss prediction errors were obtained with the USLE‐MM (exponent of the erosivity term, b₁ > 1) than the USLE‐M (b₁ = 1). A systematic error of the soil loss data is unexpected for the Sparacia soil because the calibration curve does not depend on the water level in the tank. In any case, this type of error does not have any effect on the b₁ exponent. Instead, this exponent decreases as the level of underestimation increases for increasing soil loss values. This type of error can occur at Sparacia if it is assumed that a soil loss measurement can be obtained by a bottle sampler dipped close to the bottom of the tank after mixing the suspension and assuming that the measured concentration coincides with the actual one. In this case, the risk is to obtain a lower b₁ value than the actual one. In conclusion, additional investigations on the factors determining errors in soil loss data collected by a sampling procedure are advisable because these errors can have a noticeable effect on the calibrated empirical models for soil loss prediction.  相似文献