不同预处理方法对尕海沉积物粒度测试的影响   总被引：2，自引：0，他引：2  

李华勇  潘安定  明庆忠 《干旱区地理》2011,(4)

湖泊沉积物粒度是研究湖区古环境演化的一个重要代用指标,粒度测量结果与预处理方法密切相关。从柴达木尕海湖岩心钻孔取48个样品,采用五种预处理方法,运用马尔文2000激光粒度仪进行粒度分析。结果显示经过预处理后平均粒径有不同程度的变细。单独加入H2O2除去样品中的有机质后,粒度分散变细最为明显,变幅可达10%左右,单独加入(NaPO3)6或H2O2处理后,>63μm(粗颗粒组分)粒径百分含量降低8个百分点左右。单独加蒸馏水浸泡、单独加HCl除去碳酸盐类胶结物和先后加H2O2、HCl(、NaPO3)6处理这三种方法分散效果不明显。23～33号样品对预处理的灵敏度最差,其他样品灵敏度稍好,但总体上尕海湖沉积物对预处理作用不敏感。对于性质类似的盐湖沉积物粒度测试,本文推荐加H2O2进行预处理。  相似文献   

粒子群神经网络混合模型在农用地分等中的应用     

马世发  何建华  念沛豪  张雄宇 《地理与地理信息科学》2011,27(1):105-108,115

针对常规农用地分等模型因子权重计算存在人为干扰和神经网络模型自身优化过程中易陷入局部最优的情况,该文综合了BP神经网络非线性权重数据挖掘特性和粒子群的全局优化能力,建立了农用地分等计算的粒子群神经网络混合模型(PSO-BP网络模型),并应用于广东省揭西县农用地分等计算中,发现PSO-BP网络模型能避免定级因子权重确定的人为干扰,同时具有较高的优化效率,应用效果较好。  相似文献   

沉积物粒度分析方法的比较   总被引：5，自引：0，他引：5  

冉敬  杜谷  潘忠习 《岩矿测试》2011,30(6):669-676

近年来激光粒度分析法在沉积物粒度分析方面的应用得到了进一步扩展。本文利用美国麦克奇公司生产的S3500型激光粒度分析仪开展沉积物粒度分析方法实验,研究表明:S3500型仪器较优的样品用量约为0.2 g;稀释过程会影响样品的粒度分布;样品分取方式会带来不同的随机误差。与薄片图像法和筛析法两种传统粒度分析方法获得的粒度分布参数比较表明:激光法测得的平均粒径较薄片图像法和筛析法偏细;激光法和筛析法的峰度相关性较好。采用Malvern 2000和Micro S3500两种激光粒度分析仪测量结果的比较表明:Malvern 2000测得的平均粒径较Micro S3500测得的平均粒径偏细,但二者的相关性很好(r=0.9574),研究认为这两种粒度仪的测试结果会给岩石粒度定名带来差异。由于各种粒度分析方法存在差异和局限性,在实际工作中粒度分析应尽可能建立在同一测量体系上,以便资料对比。  相似文献   

Fabric evolution within shear bands of granular materials and its relation to critical state theory   总被引：2，自引：0，他引：2  

Pengcheng Fu  Yannis F. Dafalias 《国际地质力学数值与分析法杂志》2011,35(18):1918-1948

In an effort to study the relation of fabrics to the critical states of granular aggregates, the discrete element method (DEM) is used to investigate the evolution of fabrics of virtual granular materials consisting of 2D elongated particles. Specimens with a great variety of initial fabrics in terms of void ratios, preferred particle orientations, and intensities of fabric anisotropy were fabricated and tested with direct shear and biaxial compression tests. During loading of a typical specimen, deformation naturally localizes within shear bands while the remaining of the sample stops deforming. Thus, studying the evolution of fabric requires performing continuous local fabric measurements inside these bands, a suitable task for the proposed DEM methodology. It is found that a common ultimate/critical state is eventually reached by all specimens regardless of their initial states. The ultimate/critical state is characterized by a critical void ratio e which depends on the mean stress p, while the other critical state fabric variables related to particle orientations are largely independent of p. These findings confirm the uniqueness of the critical state line in the e ? p space, and show that the critical state itself is necessarily anisotropic. Additional findings include the following: (1) shear bands are highly heterogeneous and critical states exist only in a statistical sense; (2) critical states can only be reached at very large local shear deformations, which are not always obtained by biaxial compression tests (both physical and numerical); (3) the fabric evolution processes are very complex and highly dependent on the initial fabrics. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

北京地区某基坑边坡支护变形分析及建议          下载免费PDF全文

秦俊生  王成彪  程剑 《探矿工程》2011,38(4):36-40

通过北京地区某基坑开挖工程中的变形情况,分析该工程基坑边坡变形的根本原因,同时通过该工程的情况,反思在岩土工程设计及施工过程中遇见该类饱和的细颗粒地层时应当注意的事项,最后对在此类地层中施工时的一些难点提出了解决方法。  相似文献   

利用方式对东北黑土粘土矿物组成的影响   总被引：1，自引：0，他引：1  

郑庆福  赵兰坡  冯君  王鸿斌  李春林 《矿物学报》2011,31(1):139-145

土地利用方式是影响土壤可持续利用的重要因素。粘土矿物是土壤重要的活泼物质,会受利用方式的影响而发生改变。为了揭示利用方式对土壤粘土矿物的影响,对不同利用方式下的东北黑土进行土壤理化特性及粘粒XRD分析。结果表明:荒地、旱田(大豆)、旱田(玉米)、水田利用的土壤矿物颗粒的风化依次增强,伊利石的含量和结晶度也依次降低。经水田利用后的黑土,粘土矿物的演变过程为:云母→伊利石→蛭石和绿泥石。定量结果表明黑土水田利用会出现蛭石绿泥石化现象。综合说明旱田利用会使土壤结构破坏以及水土流失加剧,而水田利用则能较好的协调土壤理化性质,可较大程度的改良土壤。  相似文献   

拉萨市夏季大气降尘单颗粒矿物组成及其形貌特征   总被引：3，自引：0，他引：3       下载免费PDF全文

张学磊  邬光剑  岳雅慧  张成龙 《岩石矿物学杂志》2011,30(1):127-134

应用带能谱的电子扫描电镜(SEM-EDX)对拉萨市夏季正常天气下收集的大气自然沉降气溶胶样品进行分析,研究了拉萨市大气降尘矿物组成和各种物相形貌特征信息。拉萨市大气颗粒物含有硅酸盐颗粒、富钙颗粒、富铁颗粒、富碳颗粒(燃煤飞灰颗粒和燃油飞灰颗粒)和植物残体颗粒。根据颗粒物数量统计发现拉萨市大气颗粒物以硅酸盐颗粒为主,富钙颗粒和富铁颗粒次之,需要指出的是以燃油飞灰为主的富碳颗粒已占到一定比重,说明以燃油为主的机动车尾气对拉萨大气污染在加强。研究结果表明,大气降尘矿物成分及其形貌特征可以用作判定污染物来源的重要标志,拉萨大气中颗粒来源的多样性决定了治理措施也应综合进行。  相似文献   

Modeled Influence of East Asian Black Carbon on Inter-Decadal Shifts in East China Summer Rainfall   总被引：1，自引：0，他引：1       下载免费PDF全文

Rashed MAHMOOD  LI Shuang-Lin 《大气和海洋科学快报》2011,4(6):349-355

Two inter-decadal shifts in East China summer rainfall during the last three decades of the 20th century have been identified.One shift occurred in the late 1970s and featured more rainfall in the Yangtze River valley and prolonged drought in North China.The other shift occurred in the early 1990s and featured increased rainfall in South China.The role of black carbon(BC) aerosol in the first shift event is controversial,and it has not been documented for the second event.In this study,the authors used Geophysical Fluid Dynamics Laboratory's(GFDL's) atmospheric general circulation model known as Atmosphere and Land Model(AM2.1) ,which has been shown to capture East Asian climate variability well,to investigate these issues by conducting sensitive experiments with or without historical BC in East Asia. The results suggest that the model reproduces the first shift well,including intensified rainfall in the Yangtze River and weakened monsoonal circulation.However,the model captures only a fraction of the observed variations for the second shift event.Thus,the role of BC in modulating the two shift events is different,and its impact is relatively less important for the early 1990s event.  相似文献   

Atmospheric Concentrations and Phase Partitioning of Polycyclic Aromatic Hydrocarbons in Izmir,Turkey   总被引：1，自引：0，他引：1  

Eylem Demircioglu  Aysun Sofuoglu  Mustafa Odabasi 《洁净——土壤、空气、水》2011,39(4):319-327

Ambient air polycyclic aromatic hydrocarbon (PAH) samples were collected at a suburban (n = 63) and at an urban site (n = 14) in Izmir, Turkey. Average gas‐phase total PAH (∑₁₄PAH) concentrations were 23.5 ng m^?3 for suburban and 109.7 ng m^?3 for urban sites while average particle‐phase total PAH concentrations were 12.3 and 34.5 ng m^?3 for suburban and urban sites, respectively. Higher ambient PAH concentrations were measured in the gas‐phase and ∑₁₄PAH concentrations were dominated by lower molecular weight PAHs. Multiple linear regression analysis indicated that the meteorological parameters were effective on ambient PAH concentrations. Emission sources of particle‐phase PAHs were investigated using a diagnostic plot of fluorene (FLN)/(fluorine + pyrene; PY) versus indeno[1,2,3‐cd]PY/(indeno[1,2,3‐cd]PY + benzo[g,h,i]perylene) and several diagnostic ratios. These approaches have indicated that traffic emissions (petroleum combustion) were the dominant PAH sources at both sites for summer and winter seasons. Experimental gas–particle partition coefficients (K_P) were compared to the predictions of octanol–air (K_OA) and soot–air (K_SA) partition coefficient models. The correlations between experimental and modeled K_P values were significant (r² = 0.79 and 0.94 for suburban and urban sites, respectively, p < 0.01). Octanol‐based absorptive partitioning model predicted lower partition coefficients especially for relatively volatile PAHs. However, overall there was a relatively good agreement between the measured K_P and soot‐based model predictions.  相似文献   

基于均值漂移的粒子滤波算法设计及其在导航数据处理中的应用     

宫轶松  归庆明  李保利  乔书波  张灵敏 《测绘学报》2011,(Z1):120-125,132

针对标准粒子滤波算法中存在的计算量大和粒子的权值退化的缺陷,将均值漂移算法和PF算法进行融合,设计基于均值漂移搜索算法的粒子滤波新算法。该算法仍遵从粒子滤波算法的计算框架,基本原理是利用MS算法对粒子的聚类作用,将均值漂移思想融合到粒子滤波算法的重要性采样过程中,对粒子集进行确定性搜索,使每个粒子收敛于局部最优值,这样粒子的状态表示更接近真实的状态分布,因此只需较少的粒子数便可达到未嵌入MS的使用大量粒子数的粒子滤波状态估计的性能,从而在缓解粒子的权值退化的同时提高粒子滤波算法的实时性。大量的数值试验和对GPS/DR组合导航数据处理的结果验证了该方法的有效性。  相似文献