The species diversity of fusulinaceans and high-frequency sea-level changes in the Carboniferous-Permian boundary section at Xikou, Zhen’an County, Shaanxi Province, China

The study on the interrelation between sea-level changes and biodiversity with its evolution has great significance for understanding the impact of global changes on organic evolution and exploring the inherent laws of life-environment coevolution in geological history. In this paper, the stratigraphic distribution of fusulinacean fauna in the Carboniferous-Permian boundary section at Xikou, Zhen’an County, Shaanxi Province, is analyzed quantitatively, and the relationship between the species diversity of fusulinaceans and relative sea-level changes is discussed. As a whole, the species numbers of fusulinacean fauna experience a rapid increase and an obvious decline in Xikou, Zhen’an County, from the Late Carboniferous to the Early Permian. There is a significant increase in species diversity around the Carboniferous-Permian boundary, which is one of the biggest bio-events of the fusulinacean fauna, and represents the radiation of Pseudoschwagerininae subfamily in the studied area. Integrated fusulinacean species diversity into sequence stratigraphic framework, detailed study suggests that the species diversity of the fusulinaceans is closely related to its relative stratigraphic location, and is essentially controlled by the sea-level changes, especially by the high-frequency sea-level changes. Generally, the species diversity of fusulinaceans is low, and the number of first and last appearance datum is small in the lower unit of high-frequency depositional cycle formed during the quick rise of the sea level; whereas the species diversity of fusulinaceans is high, and the number of first and last appearance datum is large in the upper unit of high-frequency cycle formed during the slow fall of the sea level. Within the third-order depositional sequence, the species diversity of the fusulinaceans at the first flooding surfaces and the maximum flooding surfaces is low, and it increases upward. The fusulinacean species diversity is low within the transgressive systems track, and it is high within the highstand systems track. The second-order rise and fall in sea level coincide with the bloom and decline of high order taxa of fusulinaceans.     

额尔齐斯成矿带萨尔布拉克金矿床的构造-成矿流体

萨尔布拉克金矿床位于准噶尔盆地北东缘之喀拉通克岛弧带,北邻呈北西西向展布的额尔齐斯构造挤压带,矿体受次级断裂萨尔布拉克韧性剪切带控制。据构造变形-热液蚀变-矿物共生组合特征,构造-成矿阶段划分为4个：Ⅰ韧性变形-黄铁矿化-硅化阶段;Ⅱ韧脆性变形-黄铁矿-毒砂-石英阶段;Ⅲ网脉状石英阶段（多金属硫化物阶段）;Ⅳ石英-碳酸...     

中性和不稳定层结大气的孤立行波精确解

通过研究二维准动量无辐散、无摩擦层结大气非线性方程组的行波解问题证明，非线性行波解的本质属性是由参数ｂ的符号性质决定的。当ｂ＞０时，为周期解，其周期与相应的线性周期解的周期相等；当ｂ≤０时，为孤立波解。给出了一般行波解的解析表达式。并细致地研究了中性和不稳定层结大气中的孤立行波的特征，发现中性和不稳定层结大气中存在具有类似于飑线结构特征的孤立波。指出了中性和不稳定层结大气中的一般孤立行波物理量的分布特征。     

玄武岩中刚玉巨晶的包体研究：Ⅰ.更长石包体的发现及意义

本文对山东昌乐碱性玄武岩中刚玉巨晶的更长石包体及同一地区产出的歪长石巨晶进行了电子探针、红外吸收光谱测定,讨论了更长石包体与刚玉巨晶、歪长石巨晶间的成因关系,认为刚玉巨品、歪长石巨晶以及玄武岩中的其他巨晶构成了一个结晶序列,歪长石相对较晚结晶。     

稻田甲烷排放的初级模式

本文建立了一个区域尺度稻田生态系统CH4排放的初步模式，该模式能从理论上反映稻田CH4产生、传输与排放的机理，并提供了一种估计不同区域气候和土壤条件下稻田生态系统CH4排放总量的有效方法。模式主要包括三个部分:水稻的生长、土壤有机物的分解和CH4的产生、传输及排放过程。模式分别模拟了早稻和晚稻CH4的排放，模拟结果与实测比较接近，CH4的季平均排放量，模拟值与实测值的偏差在10% 左右。模式的敏感性实验表明，温度是稻田CH4排放规律的主要控制因子。     

地震波面波空间相干性规律研究

本文选取台湾LSST、SMART-1台阵地震记录,分别计算不同间距S波和面波相干系数,采用Loh提出的相干函数模型对计算结果进行参数拟合。研究结果表明,当台站间距$ d < \text{50}\;{\rm{m}} $时,面波和S波相干系数基本相同;当台站间距$d = \text{500}\;{\rm{m}}$时,面波相干系数小于S波相干系数,且随着台站间距的增大,二者的差别逐渐增大;当台站间距$ d > \text{500}\;{\rm{m}}$时,面波空间相干性几乎不存在,可不考虑。本文给出的面波相干函数模型参数可作为大型盆地中的长大结构抗震分析时合成地震动场的参考。     

Population geography in China since the 1980s: Forging the links between population studies and human geography

This paper reviews the progress of population geography in China since the 1980s. The review results suggest that contrary to the common perception of its invisibility and marginalized status in the field, tremendous progress has been made in population geography in China since the 1980s. Population geographers have made significant contribution to the understanding of a wide range of population issues from geographical perspectives, including migration, urbanization, population distribution, the relationships between population, environment and resources, aging, marriage patterns, and migrants’ crimes, although such contribution often did not appear in the geographical circle. Furthermore, population geographers have played an indispensable role in revitalizing population studies in China and forging its links to human geography, occupying an important position in this multi-disciplinary field. Population geographers’ contribution to the areas of migration and urbanization research has been particularly significant, reflected in their leading roles in these areas’ research. The paper demonstrates that as latecomers in the field after more than 20 years of isolation, population geographers in China have gone through a process of catching up and increasing engagement with developments in social sciences and increasing interaction with social scientists since the 1980s, and have benefited greatly from it; however, there is a tendency for population geography to be increasingly alienated from the main stream human geography, a phenomenon similar to but not exactly the same as Anglo-American geography in the late 1990s and early 2000s. The paper argues that population geography is only half way in the course to forge the links between population studies and human geography, and it needs to return to geographical sciences to strike a healthy balance between the field of population studies and that of human geography, and promote its further development in a multi-disciplinary field.     

Experimental study on the pile group-soil vibration induced by railway traffic under the inclined bedrock condition

Acta Geotechnica - The aim of this paper is to study the soil vibration response of a pile group induced by train traffic resting on the inclined bedrock condition. A series of model tests on the...     

The disastrous 23 July 2009 debris flow in Xiangshui Gully, Kangding County, Southwestern China

On 23 July 2009, a catastrophic debris flows were triggered by heavy rainfall in Xiangshui gully, Kangding county, southwestern China. This debris flow originating shortly after a rainstorm with an intensity of 28 mm per hour transported a total volume of more than 480×103 m3 debris, depositing the poorly sorted sediment including boulders up to 2-3 m in diameter both onto an existing debris fans and into the river. Our primary objective for this study was to analyze the characteristics of the triggering ra...