雅鲁藏布江中下游地区湿季降雨量的空间分布模型

对于水文气象站点稀少的青藏高原山区,获得较为精确的降雨空间分布信息是进行降雨径流模拟的前提。该文利用GIS手段和多元回归方法,建立了雅鲁藏布江中下游地区旱、偏旱、正常、偏涝、涝等5种类型年份的湿季(5—9月)降雨量的空间分布模型。结果显示:多种地理地形因子对湿季降雨空间分布均有重要影响。统计分析表明:(1)雅鲁藏布江中下游流域地形复杂、降雨站点稀少,回归分析中的地理、地形因子共线性问题突出,方差扩大因子法、Pear-son相关系数法和因子分析法的组合应用是识别和解决共线性问题的有效方法;(2)影响湿季降雨的局部地形因子表达存在着最优空间尺度,15—25km半径范围内的平均坡度、平均坡向、开放度值与降雨也有较高相关性,但考虑其他局部地形因子后,开放度对降雨空间分布的影响可以忽略。     

中国大陆与香港地区风荷载规范比较研究

静力等效风荷载是结构抗风设计的重要内容,不同国家和地区的风荷载规范不同。比较了我国大陆与香港地区荷载规范中风荷载的计算方法,所得结论为有关研究和设计提供了理论依据。     

Pyrolysis of oil at high temperatures: Gas potentials, chemical and carbon isotopic signatures

Although the gas cracked from oil has been believed to be one of the important sources in highly ma-tured marine basins, there are still some debates on its resource potentials and chemical and isotopic compositions. In this study a Cambrian-sourced marine oil sample from the Silurian reservoir of well TZ62 in the central Tarim basin was pyrolyzed using sealed gold tubes with two different pyrolysis schemes: continuous pyrolysis in a closed system and stepwise semi-open pyrolysis. The results show that the maximum weight yield of C_1–5 gases occurs at EasyRo=2.3% and the residual gas poten-tial after this maturity is only 43.4 mL/g, about 12% of the yield of 361 mL/g at EasyRo=2.3%. Combined with the results of kinetic modeling, the main stage of gas generation from oil cracking is believed within the EasyRo=1.6%―2.3%. The increase in the volume yield of C_1–5 gases at EasyRo>2.3% in a closed system is mainly related to the re-cracking of previously formed C_2–5 wet gases, not the direct cracking of oil. The stepwise pyrolysis experiments show that the gas from the cracking of residual oil at EasyRo>2.3% is characterized by very high dryness index (higher than 92%) and heavy methane carbon isotopes ranging from -28.7‰ to -26.7‰, which is quite different from the gases from the con-tinuous pyrolysis in a closed system. The kinetic modeling of methane carbon isotope fractionation shows that the carbon isotopes of methane within the main stage of gas generation (EasyRo<2.3%) are far lighter than the carbon isotopes of the precursor oils under a geological heating rate of 2 ℃/Ma. The above observations and results provide some new clues to the accurate recognition and objective re-source evaluation of oil cracking gas in highly mature marine basins.     

圬工桥墩弯矩增大系数实用计算法

采用非线性计算方法，分析影响圬工桥墩弯矩增大系数各主要因素的性质，建立用于设计的弯矩增大系数实用计算公式，并通过回归分析，建立了有关系数的表达式。