西安白鹿塬全新世黄土剖面磁化率的古气候特征     

李秉成  雷祥义  李正泽  王世尧  温金梅  王艳娟  胡培华 《海洋地质与第四纪地质》2008,28(1):115-121

对西安地区全新世以来的环境演变特征进行了系统研究,建立了该地区全新世以来黄土-古土壤沉积的年代序列,揭示其反映的东亚冬、夏季风变迁规律,为预测西安地区乃至中国和全球未来环境的发展趋势提供依据。通过对西安白鹿塬刘家坡典型剖面全新世黄土-古土壤地层的岩性描述、地层划分和对比,结合泾阳县新庄村AMS14C的年代测定和其他学者的测年数据,建立了该地区全新世以来黄土沉积的年代序列。根据磁化率气候替代指标显示的曲线特征,阐述了这一替代指标在剖面上的变化规律,探讨了该黄土剖面所反映的东亚冬、夏季风强弱变化特点,详细分析了西安地区全新世以来环境变化的特征和规律,进而将该剖面磁化率曲线特征与其他学者根据孢粉谱建立的温度曲线对比,对西安地区全新世以来古气候的阶段性进行了详细分析和论证,将西安地区10000a以来的气候演变划分为7个阶段。  相似文献   

Predictions of large stress reversals in true triaxial tests on cross‐anisotropic sand     

Suresh K. Gutta  Jerry A. Yamamuro  Poul V. Lade 《国际地质力学数值与分析法杂志》2009,33(8):1013-1037

A rotational kinematic hardening constitutive model with the capability of predicting the behavior of soil during three‐dimensional stress reversals has been developed. An existing elasto‐plastic constitutive model, the Single Hardening Model, utilizing isotropic hardening serves as the basic framework in these formulations. The framework of the kinematic hardening model was discussed in a companion paper. The previously proposed cross‐anisotropic Single Hardening Model is added to the present kinematic hardening mechanism to capture inherent anisotropy of sands in addition to the stress reversals. This model involves 13 parameters, which can be determined from simple laboratory experiments, such as isotropic compression, drained triaxial compression and triaxial extension tests. The results from a series of true triaxial tests with large three‐dimensional stress reversals performed on medium dense cross‐anisotropic Santa Monica Beach sand are employed for comparison with predictions. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

THE TYPES OF LAKE IN SONGNEN PLAIN AND THEIR REGIONAL CHARACTER     

Jin-fu Lu  Dong-mei Jie  Zhi-min Li  Xue-tian Leng 《中国地理科学(英文版)》2000,10(4):366-370

The lake groups in the Songnen Plain are low plain lake groups, which are located in the temperate semihumid area in China. They are characterized by small area, shallow basin, thick density and various types. In the try for classifying comprehensively the lake groups, a classification system is developed based on three main factors, i.e. forming cause, water quantity and water quality. The most internal character can be concisely grasped through three principal indexes and three auxiliary indexes of three main factors. A sample of complicated changeable path is put forward for further analyzing and outlining these basic types, in the meantime, it’s linking up easily with the classification system of the single factor. According to the regional environment, the regional differences of the type composition and the principal types, the lake groups in the Songnen Plain can be divided into 6 sub-regions. Foundation item: Under the auspices of the National Natural Science Foundation of China(49671077). Biography: LU Jin-fu (1938–), male, professor. His research interest includes paleo-environment in the Quaternary.  相似文献   

新疆天山-北山成矿带区域地球化学特征     

王虹  刘拓  王庆明  郑启平 《地球科学与环境学报》2007,29(2):141-144

根据地质构造和矿产分布特征,将天山—北山成矿带划分为西南天山、东天山、西天山、北山4个单元。依据1∶20万水系沉积物测量数据,对比分析了主要成矿元素在整个成矿带及4个构造单元的背景值、元素的空间分布规律、元素富集特征及其与成矿的关系等。得出西南天山、西天山元素富集特征反映了以金为主的矿化特征;东天山反映以金、铜(镍)、银多金属为主的矿产格架,北山是以金为主矿化特征。  相似文献   

Rotational kinematic hardening model for three‐dimensional stress reversals in sand     

Poul V. Lade  Jerry A. Yamamuro  Suresh K. Gutta 《国际地质力学数值与分析法杂志》2009,33(7):967-991

A kinematic hardening mechanism has previously been proposed to capture the behavior of soil during large stress reversals in the triaxial plane. This mechanism is now extended to the principal stress space. It incorporates rotation and intersection of yield surfaces to achieve a consistent and physically rational fit with experimentally observed soil behavior during large three‐dimensional stress reversals. An existing elasto‐plastic model with isotropic hardening is used as the basic framework to which the rotational kinematic hardening mechanism has been added. The new combined model preserves the behavior of the isotropic hardening model under monotonic loading conditions, and the extension from isotropic to rotational kinematic hardening under three‐dimensional conditions is accomplished without introducing new material parameters. The framework of the model is presented here with some comparisons between theoretical and experimental directions of strain increment vectors to indicate the potential of the model. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

海南定安富文金矿床矿石特征   总被引：1，自引：0，他引：1  

张小文  覃海灿  傅杨荣 《地球科学与环境学报》2007,29(1):26-29

从不同标高、不同品位的矿石选矿试验研究入手,论述了富文金矿矿石的物质组成、矿物成分、结构构造、金的赋存状态等。研究表明,该金矿为中型特高硫化物含金石英脉型金矿床,矿体严格受断裂裂隙控制。矿石的有用组分多样,有害杂质少,金矿物主要为自然金。主要金属矿物为黄铁矿、毒砂,同时也是主要的载金矿物;非金属矿物为石英、碳酸盐矿物。矿石多具自形、半自形、他形粒状结构,以脉状、浸染状构造为主。自然金形态为尖角粒状、角粒状、长角粒状,赋存状态以裂隙金为主,其次为粒间金,包裹金占16.9%,自然金为细粒金。矿石类型为富金银多金属硫化物含金石英脉型。  相似文献   

Effects of grid cell size and time step length on simulation results of the Limburg soil erosion model (LISEM)     

Rudi Hessel 《水文研究》2005,19(15):3037-3049

With increasing computer power, process‐based models that use grids to discretize space have become increasingly popular. For such models, the simulation results might depend on both grid cell size and, in the case of dynamic models, on the time step length used in the model. In this study, the dynamic Limburg soil erosion model (LISEM) was applied to a small catchment on the Chinese Loess Plateau. To study the effect of grid cell size and time step length, simulations were performed for grid cell sizes ranging from 5 to 100 m for a single time step length, and for time step lengths ranging from 2 to 120 s for a single grid cell size. The results show that the LISEM results vary considerably as a function of both grid cell size and time step length. For both increase in cell size and increasing time step length, the trend was a decrease in predicted discharge and predicted soil loss. For discharge, the most important causes are likely to be a decrease in slope with increasing grid cell size, rainfall averaging for longer time step lengths, and numerical dispersion of the kinematic wave solution. For soil loss, the cause is less clear, reflecting the complexity of soil loss prediction, which depends on available water, transport capacity and sediment redistribution, all of which change in time and space. These results show that a choice for a certain grid cell size and a certain time step length should be made before calibration of the model. Similar erosion models are likely to have similar dependencies on grid size and time step length. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

《儒林外史》人物对比讽刺谈     

莫纯星 《广东海洋大学学报》2007,27(2):83-86

《儒林外史》是一部讽刺小说,主要运用对比讽刺,包括“鹤立鸡群”式、“言行相悖”式、“无独有偶”式、“前后矛盾”式、“自打嘴巴”式以及明比、暗比等讽刺。在作者的笔下,讽刺手法剥光了那些令人憎恶的封建文人、官僚豪绅、市井无赖等的外衣,露出了他们丑恶的灵魂,深刻地揭露了行将崩溃的封建制度的腐朽性,强烈地抨击了罪恶的科举制度。这种讽刺艺术在我国古代小说发展史上达到了顶峰。  相似文献   

草鱼网围养殖区声波的研究     

曹瑜  施炜纲  彭晓星 《广东海洋大学学报》2006,26(6):31-34

对网围养殖区内草鱼的活动声波进行了采集与分析,并将采集的声波进行了回放。结果表明,草鱼网围养殖区声波频率范围为0~3.2 kHz,整个频段内没有宽带波峰。在草鱼饥饿、食饵和饱食的不同状态下养殖区内的水声特性有一定的差异。研究表明在网围养殖区通过声波回放能对草鱼起到诱集作用,在投饵回放、投饵不回放及不投饵回放声波的情况下,草鱼的响应时间分别为2.55、3.504、.80 min,存在显著差异。回放持续性声波和间隔性声波在响应时间上不存在显著差异。  相似文献   

古田水口库区ML4.8地震成因探讨     

吴绍祖  陈光  关玉梅  倪晓寅 《大地测量与地球动力学》2009,29(Z1):32-36

介绍水口库区地震地质构造特征与地震活动特点，重点分析2008年3月6日古田4.8级地震序列以及震时福建地区应力场特征。分析认为：1) 2008年3月水口库区处于明显的应力积累区域；2）古田4.8级地震为构造型水库地震， NE向湾口断裂（F2）是可能的发震构造之一；3）水口水库前两次4级地震发震时间相隔近12年，表明水库水位的升降与发震之间的相关性并不明显，区域构造应力的变化是导致水口库区地震的决定因素。  相似文献