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331.
DONG Zhiming lv Junchang Research Center of Paleontology Stratigraphy Jijin University Changchun Institute of Paleontology Paleoanthropology Chinese Academy Sciences Beijing Institute of Geology Chinese Academy of Geological Sciences Beijing 《《地质学报》英文版》2005,79(2):164-167
Based on a nearly complete lower jaw from the Early Cretaceous of Liaoning Province, a new ctenochasmatid pterosaur: Liaoxipterus brachyognathus gen, et sp. nov. is erected. Liaoxipterus brachyognathus is different from any known pterosaurs with skulls preserved from western Liaoning Province and its peripheral areas in that the anterior part of the mandibular symphysis is expanded, being widest between the fourth alveolus of each side. Liaoxipterus brachyognathus is assigned to Ctenochasmatidae based on the following characters: the rounded anterior end of the lower jaw is spatulated and dorsoventrally flattened and marked heterodonty in the dentition is absent. It differs from other ctenochasmatid pterosaurs in having relatively small number of teeth. Liaoxipterus is distinguished from some ornithocheirids, which have expanded anterior parts of the mandibular symphyses, such as Anhanguera piscator,Coloborhynchus robustus in which the teeth of the new pterosaur are not as variable. 相似文献
332.
滇川西部金沙江古特提斯洋的威尔逊旋回 总被引:12,自引:0,他引:12
本文对滇川西部金沙江造山带被动大陆边缘、蛇绿岩、洋盆相放射虫硅质岩、岛弧岩浆岩和造山磨拉石建造的形成时代进行了综合研究,结合古生物化石和SHRIMP年龄,论证了金沙江古特提斯洋盆的威尔逊旋回,即大陆裂解(晚泥盆世)、洋盆扩张(石炭纪)、俯冲消减(二叠纪)和碰撞造山(三叠纪)。金沙江洋是滇川西部古特提斯多岛洋中重要的支洋盆。 相似文献
333.
长白山地区是中国泥炭分布集中地区之一。本文选择长白山地区典型的泥炭剖面--大桥剖面,探讨其沉积物常量元素和微量元素的垂直分布规律及其对全新世气候变化的指示作用,并与该区另一代表剖面--金川泥炭剖面进行对比。结果表明,泥炭中常量元素含量最大值出现在195 cm,向上、向下都减少,铁含量与灰分、容重在剖面上的变化规律基本一致,说明它主要来源于灰分;由于泥炭和砂土的基本性质,如容重、灰分、pH值有很大的区别,泥炭层微量元素大于下部砂土的含量,亚表层微量元素含量最高,这与灰分、纤维含量正好相反,与pH值剖面变化一致;沉积物容重、灰分、pH值、Ca/ Mg以及元素的富集因子、泥炭中总碳含量在剖面上的变化,显示很强的一致性,据此反映该区经历了早11880~7600aBP)、中(7 600~480aBP)、晚(2480~0aBP)全新世三个环境阶段,其结论与前人通过孢粉、同位素手段分析得到的金川泥炭剖面环境变迁规律相同,从而说明它们可以作为研究环境变迁的敏感指标。 相似文献
334.
系数矩阵存储和线性方程组求解是限制三维电磁积分方程方法发展的主要因素。Zhdanov提出准线性(QL)近似技术,建立了复杂散射场与背景场的线性关系,有效地避免了积分方程中大型线性方程组的求解,但是该算法用于多源问题航空电磁正演模拟时精度不高。因此,本文提出一种基于多重网格准线性(MGQL)近似的算法,并利用系数矩阵的Toeplitz性质存储矩阵和快速傅里叶变换,实现了矩阵与向量的快速乘积、降低了计算复杂度,采用多重网格结合了积分方程方法和准线性近似解法的优点,在保证精度的条件下提高计算速度、减少存储量。针对不同类型网格的模拟实验表明,相比于传统积分方程方法,本文算法在保证计算精度的同时,可以将计算速度极大地提高(>10倍)。 相似文献
335.
抚顺—清原地区是辽宁省最重要的铜矿产地,但近年来资源量急剧减少,开展铜矿资源进一步找矿工作已十分紧迫。文章依托"辽宁省铜矿资源潜力评价"和"辽宁省矿产地质志"项目所收集到的地、物、化、遥、自然重砂等资料,在建立红透山式铜矿找矿模型、提取证据因子的基础上,应用MRAS软件的证据权重模型模块对抚顺—清原地区红透山式铜矿进行矿产预测。共圈定找矿远景区10个,以计算得到的后验概率(P)将其划分为Ⅰ级找矿远景区4个、Ⅱ级找矿远景区3个、Ⅲ级找矿远景区3个;并利用找矿信息量预测等值线图和色块图对预测成果进行了表达。 相似文献
336.
337.
本文以郑洛地区为研究区域,以裴李岗文化时期、仰韶文化前期、仰韶文化后期和龙山文化时期为时间序列,对研究区域的流域盆地面积与相应的遗址点数量的关系、流域盆地面积与相应的遗址点增长速率的关系,以及各个流域盆地中遗址点分布密度的时空分布特征进行了研究。结果显示:(1)通过相关方法分析,以数字化的形式表明了流域盆地面积与分布的遗址点数量呈显著的正相关关系,且裴李岗文化时期的相关程度与其他3个文化时期相比较小;(2)对各流域盆地内遗址点的变化趋势分析发现,流域盆地面积与分布的遗址点变化趋势呈显著的正相关关系,这也解释了流域盆地黄河流域(B)、伊洛河流域(C)的变化趋势最快的缘由;(3)对各流域盆地内遗址点的分布密度进行分级可发现,在裴李岗文化时期,东部地区遗址点的分布密度大于西部地区,而其他3个文化时期是中西部地区大于东部地区。 相似文献
338.
Data of flood, drought, hailstorms, and low temperature events in Xinjiang from 1949 to 2012 were analyzed with the diffusion method to assess the risk of the most common types of disasters in Xinjiang. It was proved that the frequency and intensity of meteorological disasters of the study area showed an increasing trend associated with global warming. Among the four types of disasters, surpass probability of drought was the largest, followed by hailstorm, low temperature and flood in turn. Moreover, the wavelet method analysis revealed that greater oscillations had occurred since 2000, which may be associated with the occurrence of extreme climatic changes. The spatial distribution of frequencies reveals that the northern slope of Tianshan Mountains is a multiple disaster area, the southern slope of Tianshan is the area where more floods and hailstorms occur, and the west of Turpan-Hami Basin is the area wind is prevalent. The relationships between disaster-affected areas and corresponding meteorological and socio-economic indexes were also analyzed. It indicated that there were significant positive correlations between the areas affected and the most meteorological and socio-economic indicators except the grain acreage. 相似文献
339.
Based on the surface runoff, temperature and precipitation data over the last 50 years from eight representative rivers in Xinjiang, using Mann-Kendall trend and jump detection method, the paper investigated the long-term trend and jump point of time series, the surface runoff, mean annual temperature and annual precipitation. Meanwhile, the paper analyzed the relationship between runoff and temperature and precipitation, and the flood frequency and peak flow. Results showed that climate of all parts of Xinjiang conformably has experienced an increase in temperature and precipitation since the mid-1980s. Northern Xinjiang was the area that changed most significantly followed by southern and eastern Xinjiang. Affected by temperature and precipitation variation, river runoff had changed both inter- annually and intra-annually. The surface runoff of most rivers has increased significantly since the early 1990s, and some of them have even witnessed the earlier spring floods, later summer floods and increasing flood peaks. The variation characteristics were closely related with the replenishment types of rivers. Flood frequency and peak flow increased all over Xinjiang. Climate warming has had an effect on the regional hydrological cycle. 相似文献
340.
YU JunBao LIU JingShuang SUN ZhiGao SUN WeiDong WANG JinDa WANG GuoPing & CHEN XiaoBing Key Lab of Coastal Envionment Processed Yantai Institute of Coastal Zone Research for Sustainable Development Chinese Academy of Sciences Yantai China Key Lab of Wetl Ecology Environment Northeast Institute of Geography Agricultural Ecology Changchun Key Laboratory of Isotope Geochronology Geochemistry Guangzhou Institute of Geo... 《中国科学:地球科学(英文版)》2010,(5)
Nitrous oxide (N2O) and methane (CH4) emissions were measured using a static chamber method in two adjacent plots of freshwater marsh predominated by Calamagrostis angustifolia, one is seasonal waterlogged (SW) and the other without surface water accumulation (NW), in Sanjiang Plain wetland (47°35′N, 133°31′E), northeast China, during 2002-2004. The diurnal and seasonal flux variations of both gases were significantly correlated with 5-cm-soil temperature. The NW marsh is a source of N2O and sink of CH4, wh... 相似文献