Compositional effect on the pressure derivatives of bulk modulus of silicate melts   总被引：1，自引：0，他引：1  

Zhicheng Jing  Shun-ichiro Karato 《Earth and Planetary Science Letters》2008,272(1-2):429-436

Although the bulk moduli (K_T0) of silicate melts have a relatively narrow range of values, the pressure derivatives of the isothermal bulk modulus (K_T0^′) can assume a broad range of values and have an important influence on the compositional dependence of the melt compressibility at high pressure. Based on the melt density data from sink/float experiments at high pressures in the literature, we calculate K_T0^′ using an isothermal equation of state (EOS) (e.g., Birch–Murnaghan EOS and Vinet EOS) with the previously determined values of room-pressure density (ρ₀) and room-pressure bulk modulus (K_T0). The results show that best estimates of K_T0^′ vary considerably from ~ 3 to ~ 7 for different compositions. K_T0^′ is nearly independent of Mg # (molar Mg/(Mg + Fe)), but decreases with SiO₂ content. Hydrous melts have anomalously small K_T0^′ leading to a high degree of compression at high pressures. For anhydrous melts, K_T0^′ is ~ 7 for peridotitic melts, ~ 6 for picritic melts, ~ 5 for komatiitic melts, and ~ 4 for basaltic melts.  相似文献   

海岛建设引发的植被覆盖度变化的遥感分析     

温小乐  李洋  林征峰 《地球信息科学学报》2017,19(2):273-280

海岛生态脆弱、稳定性差,大规模的海岛开发使得原本脆弱的岛上植被生境面临更大的威胁,对海岛开发中的植被覆盖变化开展分析显得尤为重要。本文基于Landsat 5卫星和Landsat 8卫星的2001、2010和2014年的遥感影像,采用Gutmand和Ignatov提出的植被覆盖度计算模型提取福建平潭岛的植被覆盖度,并结合其土地覆盖变化信息,探究平潭综合实验区建设前后植被覆盖度变化特点及其原因。研究结果表明,3个时相的平潭岛植被覆盖度达中度以上的区域面积比例分别为86.00%、58.92%和71.16%,表明研究区整体植被覆盖状况良好。动态变化分析结果显示,2001-2014年研究区植被覆盖度总体呈下降趋势,其中2001-2010年植被覆盖度下降显著,下降区域面积比例高达53.95%;而2010-2014年岛上植被覆盖状况有较大改善,植被覆盖度增加区域面积比例达47.77%,这在一定程度上弥补了之前植被覆盖度大幅下降的影响,分析原因主要得益于平潭综合实验区建立后所采取的科学规划、进一步加大植树造林、逐步完善海岛绿地系统的植被建设与保护措施。  相似文献   

重力场向下延拓的三阶Adams-Bashforth公式法     

张冲  黄大年  秦朋波  吴国超  方刚 《吉林大学学报(地球科学版)》2017,(5):1533-1542

重力场向上延拓是稳定且收敛的过程,而向下延拓是不稳定且发散的过程。为此,本文提出一种重力场向下延拓新方法。首先,对重力场及其垂向一阶导数向上延拓,得到不同高度的重力场垂向导数;然后,基于求解微分方程的三阶Adams-Bashforth多步法,推导出稳定的向下延拓公式;最后,为验证本文方法,将其分别应用于模型数据和实际数据。理论模型试验及误差曲线表明,相对于经典下延方法——傅里叶变换下延法和积分迭代下延法,新方法三阶Adams-Bashforth公式法下延过程稳定,边界效应不明显,下延深度可达5倍点距,下延结果与真实值的相对误差更小,结果更准确。将本文方法应用于加拿大某区实测航空重力数据,得到有效且准确的下延结果,能够识别和圈定一些细小异常特征。  相似文献   

The scientific legacy of Harold Edwin Hurst (1880–1978)     

P.E. O’Connell  D. Koutsoyiannis  H. F. Lins  Y. Markonis  A. Montanari  T. Cohn 《水文科学杂志》2016,61(9):1571-1590

ABSTRACT

Emanating from his remarkable characterization of long-term variability in geophysical records in the early 1950s, Hurst’s scientific legacy to hydrology and other disciplines is explored. A statistical explanation of the so-called “Hurst Phenomenon” did not emerge until 1968 when Mandelbrot and co-authors proposed fractional Gaussian noise based on the hypothesis of infinite memory. A vibrant hydrological literature ensued where alternative modelling representations were explored and debated, e.g. ARMA models, the Broken Line model, shifting mean models with no memory, FARIMA models, and Hurst-Kolmogorov dynamics, acknowledging a link with the work of Kolmogorov in 1940. The diffusion of Hurst’s work beyond hydrology is summarized by discipline and citations, showing that he arguably has the largest scientific footprint of any hydrologist in the last century. Its particular relevance to the modelling of long-term climatic variability in the era of climate change is discussed. Links to various long-term modes of variability in the climate system, driven by fluctuations in sea surface temperatures and ocean dynamics, are explored. Several issues related to the Hurst Phenomenon in hydrology remain as a challenge for future research.