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911.
912.
根据地球真极移和地壳运动关系的规律,以华北为例,阐明中国大陆南移的观点。从200Ma到180Ma的真极移,应在我国中部或西部。根据真极移引起地球形状调节的假说,大陆块从高纬度地区沿真极移面向赤道道运动时一般成为碎片,这和所见的地质现象一致。 相似文献
913.
针对采矿后遗留的采空区会诱发严重的地质灾害问题,该文提出一种采空区几何参数的反演算法,旨在及时探明采空区的分布特征与几何形状,进而有效控制灾害的发生.该文通过合成孔径雷达差分干涉(D-InSAR)技术获取采空区上方的地表连续沉降场,通过概率积分模型建立采空区几何特征与地表沉降场之间的相互关系,引入BFGS最优化算法对采空区的几何参数进行反演.仿真实验结果表明:在加入5 mm随机误差的情况下,BFGS算法能够有效反演出全部参数,且反演精度略高于遗传算法(SA)和模拟退火(GA)算法;同时,在不同的初值条件下,BFGS算法反演结果的数值稳定性与反演精度仍明显优于其他两种算法.工程应用中,反演结果显示SA与GA算法的相对误差平均值都超过了 10%,而BFGS算法的相对误差平均值只有4.73%,进一步验证了 BFGS算法的可靠性. 相似文献
914.
LiPing Li ChunYan Zhang Eimear Nic Lughadha Tarciso CCLeão Kate Hardwick YaoMin Zheng HuaWei Wan Ming Ma Nurbay Abudusalih Ying Hai Zhen Pu JiangShan Lai ZhanFeng Shen Li Liu Tuo Wang YangMing Jiang HuiHui Zhao QingJie Liu 《寒旱区科学》2022,14(1):54-67
Patterns in species geographic range size are relatively well-known for vertebrates,but still poorly known for plants.Contrasts of these patterns between groups have rarely been investigated.With a detailed flora and fauna distribution database of Xinjiang,China,we used regression methods,redundancy analysis and random forests to explore the relationship of environment and body size with the geographic range size of plants,mammals and birds in Xinjiang and contrast these patterns between plants and animals.We found positive correlations between species range size and body size.The range size of plants was more influenced by water variables,while that of mammals and birds was largely influenced by temperature variables.The productivity variable,i.e.,Enhanced Vegetation Index(EVI)was far more correlated with range size than climatic variables for both plants and animals,suggesting that vegetation productivity inferred from remote sensing data may be a good predictor of species range size for both plants and animals. 相似文献
915.
Liu XiaoHong Shao XueMei Wang LiLi Zhao LiangJu Wu Pu Chen Tuo Qin DaHe Ren JiaWen 《中国科学D辑(英文版)》2007,50(7):1076-1085
In the reconstruction of past climate using stable carbon isotope composition (δ13C) in tree ring, the responses of the stable carbon composition (δ13C) of multiple tree species to environmental factors must be known detailedly. This study presented two δ13C series in annual tree rings for Chinese hemlock (Tsuga chinensis Pritz) and alpine pine (Pinus densata Mast), and investigated the relationships between climatic parameters and stable carbon discrimination (Δ13C) series, and evaluated the potential of climatic reconstruction using Δ13C in both species, in a temperate-moist region of Chuanxi Plateau, China. The raw δ13C series of the two species was inconsistent, which may be a result of different responses caused by tree's inherent physiological differences. After removing the low-frequency effects of CO2 concentration, the high-frequency (year-to-year) inter-series correlation of Δ13C was strong, indicating that Δ13C of the two tree species were controlled by common environmental conditions. The Δ13C series of the species were most significantly correlated with temperature and moisture stress, but in different periods and intensity between the species. During the physiological year, the impacts of temperature and moisture stress on Δ13C occur earlier for Chinese hemlock (previous December to February for moisture stress and February to April for temperature, respectively) than for alpine pine (March to May for moisture stress and April to July for temperature, respectively). In addition, in temperatemoist regions, the control on Δ13C of single climatic parameter was not strongly dominant and the optimal multiple regressions functions just explained the 38.5% variance of the total. Therefore, there is limited potential for using δ13C alone to identify clear, reliable climatic signals from two species. 相似文献
916.
Xingting Pu 《Astrophysics and Space Science》2012,337(1):331-334
Using a homogenous sample of 1962 quasars with redshift 3.0≤z≲4.5 drawn from the Sloan Digital Sky Survey (SDSS), we study the relationships between radio loudness, virial black hole
(BH) mass and Eddington ratio (accretion rate relative to the Eddington limit). For the radio-detected objects, we find a
significant (>99.5 per cent) anticorrelation between radio loudness R parameter and BH mass, consistent with previous studies of low-redshift radio-loud quasars. The truly radio-loud quasars
(R>30) are found to be confined to M
BH≲1010 M⊙ within our sample. We also find that R is only weakly correlated with Eddington ratio L
bol/L
Edd. Combined with previous results on the low-redshift R−L
bol/L
Edd relation, this result indicates no strong L
bol/L
Edd dependence of R at L
bol/L
Edd≳10−2. On the other hand, the large scatter in these relationships suggests that other physical properties such as BH spin and
quasar clustering must also play an important role in quasar radio emission. 相似文献
917.
918.
Ecosystem service valuation of bays in East China Sea and its response to sea reclamation activities
Liu Ruiqing Xu Hao Li Jialin Pu Ruiliang Sun Chao Cao Luodan Jiang Yimei Tian Peng Wang Lijia Gong Hongbo 《地理学报(英文版)》2020,30(7):1095-1116
Journal of Geographical Sciences - Ecosystem service values (ESVs) of bays and their response to sea reclamation are of great practical importance for forming bay eco-compensation policy and... 相似文献
919.
连续强沙尘天气的发展和时空演变机制的数值模拟 总被引:2,自引:8,他引:2
2002年4月6-8日由蒙古气旋和地面冷锋引发了一次连续沙尘暴天气,特别是内蒙古中东部、华北和东北大部分地区沙尘持续影响时间较长,强度大。利用与非静力平衡中尺度气象模式完全耦合的区域沙尘数值模式,模拟研究这次强沙尘天气过程中沙尘浓度的空间分布结构和时间演变趋势。模拟结果与地面天气观测、定点沙尘颗粒物浓度观测资料进行对比和检验。结果表明:沙尘数值模式较逼真地刻画出这次连续强沙尘天气的形成、发展、移动、减弱的全过程;客观地揭示了强沙尘天气过程的垂直分布结构和沙尘浓度的时空演变机制;模拟的强沙尘以及输送至下游的浮尘天气范围、强度和出现时间与实况基本一致,特别是对我国华北和东北沙尘的模拟相当成功。高时空分辨率的数值模式对研究沙尘的发生、发展机制和预报预警有重要意义。 相似文献
920.
冕西稀土成矿带成矿条件探讨 总被引:7,自引:0,他引:7
该区之南河断裂及雅龙江断裂是成岩成矿流体的通道,控制了矿带的展布。哈哈、棉沙湾次级断裂带的有利部位直接控制了矿床的产出,更次级的断层、节理为矿脉、矿体提供了良好的赋存空间;霓石碱性花岗岩是稀土成矿的直接母岩,矿床与之紧密共生。含矿杂岩体的生成过程就是稀土成矿的过程,它的发育程度,决定矿床规模和价值,成矿带内已发现的稀土矿床均为充填断裂带的脉型矿床。深部构造+北北东走向地壳深断裂带+幔质碱性杂岩体“三位一体”是基本的成矿条件和模式。区内具有良好的找矿远景。 相似文献