干旱及高寒荒漠区土壤温湿度特征及相互影响的分析

根据黑河试验1991年6月20日～8月21日、1990年12月17日～2月15日每天48个时次和第二次青藏高原试验改则及狮泉河1998年全年每天24个时次的土壤温湿度资料，采用功率谱分析、PCA分析等方法，分析了干旱及高寒荒漠区两种典型下垫面土壤温湿度的时空分布特征及其相互作用。结果表明：土壤温度除日和年变化周期外还存在6～30天的不同周期；下垫面的非均匀性及其季节变化及温度梯度变化对土壤水分运动有很大的影响，冬季温度梯度变化对土壤含水量的影响大于夏季温度梯度对土壤含水量变化的影响，且温度梯度与水分运动方向相反。     

NCEP 全球预报系统在ARM SGP站点预报大气温度、湿度和云量的检验

利用美国大气辐射测量项目(ARM)制作的“气候模拟最佳估计”(CMBE)观测数据集,检验美国环境预报中心(NCEP)全球预报系统(GFS)2001～2008年在ARM Southern Great Plains(SGP)站点预报的大气温度、相对湿度和云量的垂直分布,主要结论如下:(1)NCEP GFS较好地预报出了温度...     

基于近红外岩心光谱扫描技术研究鄂尔多斯盆地彭阳铀矿床矿物分布特征

砂岩型铀矿作为一种以表生流体作用为主的后生矿床,发育较多低温矿物。甘肃省彭阳铀矿是近年来新发现的一处深部砂岩型铀矿床,具有砂体规模大、铀矿化面积广、厚度大、等特点。在含矿层及周边发育方解石、石膏、黄铁矿、黏土矿物等低温成因矿物,研究矿物的空间分布特征及其与铀矿物的关系,对判别成矿流体的主要来源、性质以及对铀成矿的控制作用具有重要意义。近红外岩心光谱扫描技术可无损、快速、批量地识别出岩心中的层状硅酸盐矿物(如高岭石、蒙脱石、绢云母等),硫酸盐矿物(如石膏、明矾石等),碳酸盐矿物(如方解石、白云石等)等矿物信息,本文基于该技术对彭阳铀矿床的矿物类型及其组合进行研究。结果表明：洛河组发育高岭石、蒙脱石、伊利石(伊/蒙混层)、绿泥石、碳酸盐、石膏、铁氧化物等矿物,铀矿段的矿物组合为“伊利石(伊/蒙混层)+石膏+碳酸盐”,局部可见高岭石。根据矿物组合特征反演流体作用,洛河组含铀矿段矿在沉积期主要是一套碱性环境,成矿期存在还原性酸性流体的注入。     

The Characteristics of Storm Wave Behavior and Its Effect on Cage Culture Using the ADCIRC+SWAN Model in Houshui Bay,China

The current storm wave hazard assessment tends to rely on a statistical method using wave models and fewer historical data which do not consider the effects of tidal and storm surge.In this paper,the wave-current coupled model ADCIRC+SWAN was used to hindcast storm events in the last 30 years.We simulated storm wave on the basis of a large set of historical storms in the North-West Pacific Basin between 1985 and 2015 in Houshui Bay using the wave-current coupled model ADCIRC+SWAN to obtain the storm wave level maps.The results were used for the statistical analysis of the maximum significant wave heights in Houshui Bay and the behavior of wave associated with storm track.Comparisons made between observations and simulated results during typhoon Rammasun(2014)indicate agreement.In addition,results demonstrate that significant wave height in Houshui Bay is dominated by the storm wind velocity and the storm track.Two groups of synthetic storm tracks were designed to further investigate the worst case of typhoon scenarios.The storm wave analysis method developed for the Houshui Bay is significant in assisting government's decision-making in rational planning of deep sea net-cage culture.The method can be applied to other bays in the Hainan Island as well.     

河北张家口金矿黄铁矿的标型特征及其成因意义

黄铁矿是张家口金矿中一种十分重要的载金矿物。泰文通过对黄铁矿的形态、粒度、成分、晶胞参数及其热电性等矿物标型的详细研究,发现当细粒,立方体与五角十二面体晶形共同出现,含较高的As,Co和Ni,晶胞参数大以及具有较高热电系数值时的黄铁矿含金性好。综合黄铁矿的这些标型特征所蕴藏的成因信息,可以得出:张家口金矿为中深成中高温变质热液矿床。     

一种基于全局优化的交错网格有限差分法

在地震波场数值模拟中, 交错网格有限差分技术得到了广泛的应用, 但是在弹性模量变化较大时, 通常会因插值而导致模拟误差增大. 旋转交错网格可以很好地克服这个缺点, 因而适合于各向异性介质正演模拟. 但是对于同样大小的网格单元, 旋转交错网格需要的步长比常规交错网格要大, 这会使梯度和散度算子的误差增大因而更易产生空间数值频散. 针对这些问题, 本文提出了旋转交错网格与紧致有限差分相结合的方法, 并基于模拟退火算法进行全局优化, 压制数值频散, 拓宽波数范围. 数值模拟结果表明, 此方法可以有效地压制数值频散, 且具有较高的模拟精度.      

A nonstationary parameter model for the sandstone creep tests

The rock masses of hydro-fluctuation belt experience seepage pressure following impoundment in the Three Gorges Reservoir; its creep behaviors are significant for reservoir bank slopes. To study the creep behaviors under seepage pressure (0, 1.45, and 1.75 MPa), we performed creep tests using representative landslide sandstone in the Three Gorges Reservoir and investigated the sandstone creep behaviors under the coupling effects of seepage pressure and stress. Previous researches on rocks have usually regarded the creep constitutive parameter as a constant; however, in this study, a nonlinear, nonstationary, plastic-viscous (NNPV) creep model which can describe the curve of sandstone creep tests is proposed. The rock-creep parameters under three levels of seepage pressure were identified, and theoretical curves using the NNPV model agreed well with the experimental data, indicating that the new model cannot only describe the primary creep and secondary creep stages under varying seepage pressures but also, in particular, perfectly describes the tertiary creep stage. Finally, the sensitivity of the NNPV model parameters is analyzed, and the result shows that the nonstationary coefficient α and the nonlinear coefficient m are main parameters affecting the tertiary creep stage.     

不同砾石覆盖度戈壁床面风蚀速率定量模拟

通过风洞实验,利用称重传感器自动记录风蚀观测样方重量变化过程,对供沙条件下不同砾石覆盖度戈壁床面风蚀速率进行了定量模拟研究。结果表明:砾石覆盖度是影响戈壁风蚀速率的关键因子,戈壁床面风蚀速率随砾石覆盖度增加按指数规律递减。各实验风速下,砾石覆盖度>50%时,戈壁床面风蚀速率随砾石覆盖度增加而减小量有限,甚至无风蚀发生;而盖度从10%到50%时,风蚀速率显著减小。因此,两种实验粒径砾石(3 cm与4 cm)至少在50%盖度时才能达到较好的风蚀防治效果。戈壁风蚀防护机理主要是砾石覆盖度的增加增大了砾石间沙粒的临界起动剪切风速,而且减少了作用在砾石间可蚀地表的剪切压。与沙质对照床面相比,10%~90%砾石盖度戈壁床面沙粒临界起动剪切风速增大了0.8~3.4倍,只有0.5％~28%的剪切压作用在砾石间可蚀地表。     

Deformation mechanism of strain localization in 2D numerical interface tests

Heterogeneity arises in soil subjected to interface shearing, with the strain gradually localizing into a band area. How the strain localization accumulates and develops to form the structure is crucial in explaining some significant constitutive behaviors of the soil–structural interface during shearing, for example, stress hardening, softening, and shear-dilatancy. Using DEM simulation, interface shear tests with a periodic boundary condition are performed to investigate the strain localization process in densely and loosely packed granular soils. Based on the velocity field given by grains’ translational and rotational velocities, several kinematic quantities are analyzed during the loading history to demonstrate the evolution of strain localization. Results suggest that tiny concentrations in the shear deformation have already been observed in the very early stage of the shear test. The degree of the strain localization, quantified by a proposed new indicator, α, steadily ascends during the stress-hardening regime, dramatically jumps prior to the stress peak, and stabilizes at the stress steady state. Loose specimen does not develop a steady pattern at the large strain, as the deformation pattern transforms between localized and diffused failure modes. During the stress steady state of both specimens, remarkable correlations are observed between α and the shear stress, as well as between α and the volumetric strain rate.     

Evolution of Quaternary groundwater system in North China Plain

The Quaternary groundwater system in the North China Plain is formed mainly through the terrestrial water flow action on the united geological and tectonic backgrounds. The analysis of groundwater dynamic field, simulation of groundwater geochemistry, and the¹⁴C dating and extraction of isotope information have provided more evidence for recognizing and assessing the evolution of groundwater circulation system and studying the past global changes. The exploitation and utilization of groundwater on a large scale and overexploitation have given rise to the decline of regional groundwater level, change of flow field, decrease of water resources and downward movement of saline water body. The water environment has entered a new evolution stage in which it is intensely disturbed by the mankind’s activities. Project supported by the National Natural Science Foundation of China.