宝钢地区钢管桩土芯闭塞性状研究

开口钢管桩在沉桩过程中,桩端土一部分将进入管内形成"土塞"或"土芯",一部分则被挤进土的四周.土芯进入管内的高度,将直接影响桩的设计.土芯闭塞的研究具有代表性的有山原法、田岛法等.对土芯高度能否做到事先预估,就宝钢地区的钢管桩土芯闭塞的实测资料经过整理分析拟合得到D-η曲线,并与实测值及山原法作比较,得到较合理的预估值.重点讨论了在宝钢地区开口钢管桩的桩径D对η的影响,可推断其它桩径在这一地区的沉桩的土芯高度,土芯承担的荷载,钢管桩的应力场,位移场.亦为相似工程提供可能的参考.     

Analyse isotopique de l'air piégé dans la glace pour quantifier les variations de température

Isotopic measurements in polar ice core have shown a succession of rapid warming periods during the last glacial period over Greenland. However, this method underestimates the surface temperature variations. A new method based on gas thermal diffusion in the firn manages to quantify surface temperature variations through associated isotopic fractionations. We developed a method to extract air from the ice and to perform isotopic measurements to reduce analytical uncertainties to 0.006 and 0.020$\text{‰}$ for δ¹⁵N and δ⁴⁰Ar. It led to a 16±1.5 °C surface temperature variation during a rapid warming ($\text{?70}\text{000}$ yr). To cite this article: A. Landais et al., C. R. Geoscience 336 (2004).     

南海及邻域弱对流云系活动的TBB资料特征

利用日本气象研究厅提供的 1 980～ 1 997年共 1 8年 3小时一次的TBB资料 ,采用统计TBB≤ - 2 8℃出现频率的方法 ,研究了南海及邻域对流活动的区域统计分布特征     

春季滇东南强对流天气的高空环境场分析

应用云南蒙自探空站2001～2004年的高空风、特性层资料分析了滇东南上空冬、春季副热带急流的时空分布特点及其对大气层结的影响,结合蒙自711数字化雷达站在其春季(3～4月)中观测到的强冰雹云回波进行分析。结果表明,春季高空副热带急流是造成滇东南地区大气不稳定层结的重要因子之一,天气系统触发不稳定大气层结产生强冰雹云,副热带急流具有加强、维持发展的作用。     

Connectivity of molten Fe alloy in peridotite based on in situ electrical conductivity measurements: implications for core formation in terrestrial planets

The connectivity of molten Fe-S in peridotite has been experimentally investigated by means of in situ electrical conductivity measurements at high temperatures and 1 GPa. Starting materials were powdered mixtures of peridotite KLB-1 with various amounts (0, 3, 6, 13, 19, 24 vol.%) of the 1 GPa eutectic composition in the Fe-FeS binary system. At temperatures above the eutectic point in the Fe-FeS system (∼980 °C) and below the solidus of KLB1 (∼1200 °C), molten Fe-S in a solid silicate matrix interconnects when the volume fraction is over ∼5%. Conductivity-temperature paths indicate that in the presence of partial silicate melting the connectivity of molten Fe-S in a peridotite matrix is inhibited. Based on observations of retrieved samples, the percolation threshold of Fe-S melts in the presence of low to moderate degrees of silicate melt is estimated at 13±2 vol.%. These results indicate that if the volume fraction of Fe-alloy in a planetesimal was initially greater than 5%, and if early heating by decay of radionuclides raised the temperature of the interior above the Fe-alloy melting point, initial metal segregation was controlled by permeable flow of molten iron alloy in a solid silicate matrix. These conditions were likely met by many terrestrial objects in the early solar nebula. Efficient removal of residual Fe-alloy (5 vol.%) from silicate requires high-degree melting of silicate so that metal can segregate as droplets. Giant impacts during the final stage of accretion of large planetary objects could supply the energy required for high-degrees of melting. Alternatively, if initial metal segregation were delayed until a planetary object grew to large size (∼1000 km in diameter), release of gravitational potential energy due to metal segregation could contribute enough heat to form a magma ocean.     

基于IP核的RAM VHDL设计

介绍了VHDL(Very High Speed Integrated Circuit Hardware DescHption Language)语言和IP核的特点，通过实例，详细阐述了IP核的使用方法和步骤，最后初步阐述了电路的优化方法。     

球层中的非线性自由热对流变粘度模型

粘度为常数或仅随深度变化是地幔对流模型中常用的假设. 本文在常粘度背景下， 通过假定小扰动粘度在纬向上的变化形式， 将粘度的横向变化引入地幔对流模型中， 并给出了变粘度地幔对流模型的数值解法. 对外边界为刚性、 内边界为应力自由（简记为R-F边界）和内外边界均为刚性（简记为R-R边界）边界的两种模型进行了计算， 对比了不同模型、 深度和瑞利数时的环型场的变化特征. 注意到环型场能量主要集中在球层的中、 上部区域， 其速度仅占总速度的几个百分点， 这个比例几乎不随瑞利数的变化而改变， 但其对流图样受瑞利数的影响较大. 环型场的对流形态和速度的分布特征表现出了明显的纬向差异， 这一结果清晰地反映出地幔粘度的横向变化对对流形态的影响. 目前的工作还只是初步的， 但为我们探讨全球大地构造上的某些现象， 例如南北半球的不对称性和差速旋转问题提供了一种可能的研究思路.