Numerical modeling of the elastoplastic damage behavior of dry and saturated concrete targets subjected to rigid projectile penetration

The objective of the present paper is to present a numerical study on the penetration performance of concrete targets with 2 different water contents. Numerical analysis has been performed by using the finite element code Abaqus/Explicit, in which a coupled elastoplastic damage model has been developed for saturated/unsaturated concrete under a wide range of confining pressures. The performance of proposed model has been firstly verified by simulating the triaxial compression tests and penetration tests realized with saturated/dry concretes. Comparisons of available experimental results and numerical simulations show that the proposed model is able to reproduce satisfactorily the mechanical behavior of saturated and dry concretes. A higher failure stress and a more important pores closing are generally obtained in dry concrete samples with respect to saturated ones. Furthermore, the main observed patterns of penetration test realized with saturated concrete targets are also satisfactorily simulated by the numerical results. Therefore, the proposed model is used to numerically predict the penetration performance of dry concrete target, and the penetration performance of dry/saturated concrete target is discussed. We observe that in dry concrete target, the penetration of projectile is strongly declined, and a smaller damage zone is created. The numerical predictions and discussions can help engineers to enhance their understandings on the influence of hydraulic conditions on structural vulnerability of concrete structures subjected to near‐field detonations or impacts.     

岩石的热模型分析

在几种岩石热辐射理论模型分析的基础上,考虑到岩石的红外光谱辐射特性和岩石的热性质──热惯量,建立岩石的热传输模型,并将实测数据代人,对岩石表面的一个日照周期内的变化做出计算,绘制出不同热惯量的几种岩石在日周期内表面温度变化曲线。由曲线看出,岩石热惯量大,其昼夜辐射温度变化小;热惯量小的岩石其昼夜辐射温差大。改变岩石的反照率、辐射系数和地面径向热流而得到岩石表面温度日变化曲线,可看出这３个因素只是改变了温度的量值,不像热惯量那样改变曲线的形状。     

地震孕育过程中地磁日变规律的分析

为了探索地震短临预报的规律,选用1991～2003年洛阳及邻区的22个ML4．0以上地震,对于洛阳台、卢氏台的地磁垂直分量资料进行综合分析,认为中强地震前45天内,Z曲线形态会出现异常变化,表现为低点时间位移、W型双低值现象、低值区、曲线平缓等多种异常。当出现2种以上异常或3次以上异常,未来3个月内,洛阳及邻区可能发生中强地震(概率为0．73)。     

中国三北地区荒漠化区域分类与发展趋势综合研究

中国北方土地荒漠化主要受青藏高原隆升以来形成的构造-沉积特征、水文地质条件、全球气候变化、尤其是亚洲季风等地质背景控制。本文仅对北方沙质荒漠化、水蚀荒漠化两种主要的荒漠化类型的区域地质分布、成因及其发展趋势进行探讨。三北地区沙质荒漠化依成因可分为:就地起沙型、风沙侵入型和土地粗粒化型等。就地起沙型沙质荒漠化主要分布在西部内陆盆地周缘冲洪积扇上,中东部高原、冲积平原上的沙漠边缘地带、沙地内部和流经这些沙漠和沙地的古河道,以及河湖相砂质沉积物和以砂质沉积物为母质的土壤分布区;风沙侵入型沙质荒漠化主要分布在上述沙漠、沙地边缘的下风地带,如巴丹吉林沙漠和腾格里沙漠的东南缘、毛乌素沙地以南的覆沙黄土区、科尔沁沙地以东的辽河平原等;土地粗化主要分布在西部盆地沙漠与戈壁的过渡地带、中东部高原砾质沙草原。沙质荒漠化在毛乌素、科尔沁和浑善达克等沙地、河西走廊的局部地区有所逆转,但三北地区总体上仍呈恶化趋势,尤其是以地表土壤粗化为主的沙质荒漠化的发展更应引起人们的关注。水蚀荒漠化依地质背景之不同可分为土漠化和岩漠化两类,前者主要分布在北方中部黄土高原地区、内蒙古科尔沁沙地南侧的黄土分布区等;后者主要分布于太行山北部、辽宁西北部的基岩山区。晋陕蒙交界地带、甘肃平凉北部、定西地区和科尔沁沙地东南的蒙辽交界处等地水蚀荒漠化形势严峻;以小流域水土流失为主的治理工程使陕西的吴旗、延安、洛川等地和朝阳河中上游地区水蚀荒漠化有所好转。总之,第四纪以来的构造2沉积特征控制着不同类型荒漠化的区域分布,气候变化和水文地质条件控制着荒漠化的进程,人类不合理的经济活动则更是荒漠化过程的催化剂,尽管在局部、在一定的时间段内可使这一过程得以缓解甚至逆转。     

Important progress on the use of isotope techniques and methods in catchment hydrology

The use of isotope techniques and methods in catchment hydrology in the last 50 years has generated two major types of progress: (1) Assessment of the temporal variations of the major stocks and flows of water in catchments, from which the estimation of wa-ter residence times is introduced in this paper. (2) Assessment of catchment hydrologic processes, in which the interactions be-tween different waters, hydrographical separation, and bio-geochemical process are described by using isotopes tracers. Future progress on isotope techniques and methods in hydrology is toward the understanding of the hydrological process in large river basins. Much potential also waits realization in terms of how isotope information may be used to calibrate and test distributed rainfall-runoff models and regarding aid in the quantification of sustainable water resources management.     

南极中山站附近冰盖近地面层湍流参数的观测研究

利用2007/2008年中国第24次南极考察队在南极中山站附近冰盖上观测试验获得的湍流脉动及相关资料,对原始资料通过坐标旋转订正后,应用涡动相关法计算分析了冰盖近地面层的湍流强度(I)、稳定度参数(z/L)、摩擦速度(u*)、拖曳系数(Cd)、地表粗糙度(z0)及动量通量(τ)和感热通量(H),并与空气动力学方法的计算结果进行对比。结果表明,Louis方案能够较好地模拟近地面层湍流通量;在平均状态下,全天雪面以感热形式从大气获得净的能量;近中性层结下地表粗糙度z0为4.54×10-4m,拖曳系数Cd=1.7×10-3,在非中性条件下,稳定度越小Cd越大,反之,则稳定度越大Cd越小。     

Erratum to: Recovery of gonadal development in tiger puffer Takifugu rubripes after exposure to 17β-estradiol during early life stages

Journal of Oceanology and Limnology - A mistake was found in Section 2.2. The current expression is “In each treatment group, juveniles were exposed to E2 at the set concentration for 2 h...     

矿山环境遥感动态监测中的相对辐射校正方法研究

多时相不变特征集(TIC)方法是一种简单而有效的相对辐射校正方法,该方法通过反射率基本不随时间变化地物的高密度中心确定线性回归方程,与目前国内多采用的伪不变特征点(PIF)方法相比,在反射率基本不随时间变化的地物数量较少时,不受反射率发生变化地物的干扰。在植被覆盖程度高、城镇点较少的矿山环境中,反射率基本不随时间变化的地物较少,因此TIC方法适用于矿山环境遥感动态监测。以鄂东南多金属矿区为研究区,使用TM数据,采用TIC方法对不同时相的归一化植被指数(NDVI)进行了相对辐射校正,有效地减小了辐射差异,实现了多时相遥感图像的辐射归一化。     

岩石实验室光谱对应分析

成像光谱图像具有几十个窄波段和高的光谱分辨率,使直接识别岩石岩性成为可能,但其海量数据又为数据的处理、分析和应用带来了不便。因此就需要寻求一种在不损失信息或最大限度保持原有信息的前提下又压缩或最小化数据量的方法。在对岩石实验室光谱按成像光谱仪（ＭＡＩＳ）通道重采样后,应用了一种特征信息提取的方法（对应分析法）,对岩石光谱进行了分析,达到了压缩数据与岩石分类的目的,同时也探讨了其处理大数据量成像光谱图像数据的意义