考虑地表径流与地下渗流耦合的斜坡降雨入渗研究

为简化分析，在模拟斜坡降雨入渗暂态渗流时，通常没有考虑入渗和产流的耦合过程。笔者提出了一种新的考虑地表径流与地下渗流耦合的斜坡降雨入渗分析方法，它较好地模拟了入渗和产流的过程，并通过算例，研究了考虑与不考虑该耦合作用对斜坡孔隙水压力分布的影响。     

Computation of Long-Term Statistical Properties of Wave Agitation in Harbors

In this paper,the long-term statistical properties of wave height in an idealized square harborwith a partial opening are studied.The incident waves are propagated into the harbor numerically by the fi-nite/infinite element method using three different wave models:(1)monochromatic wave train,(2)long-crested random wave train,and(3)short-crested random wave train.This study shows that for a giv-en incident wave,the wave height in the harbor is affected by the wave model used.For long-term estima-tion of wave height exceedance probability,it is recommended that the waves be propagated into the har-bor using the random wave model,and that wave heights be computed by use of the Rayleigh probabilitydistribution.     

Stable isotope records of plant cover change and monsoon variation in the past 2200 years: evidence from laminated stalagmites in Beijing, China

Two stalagmites collected from the Shihua cave in the southwestern suburb of Beijing were dated by annual layer counting. The results are consistent with thermal ionization mass spectrometry 230 Th dating. Stable carbon isotope variation of stalagmites is dominated by plant cover change, which largely reflects climate change and monsoon variation. Oxygen isotopes are mainly affected by precipitation, which is related to summer and winter monsoon intensity. The combination of carbon and oxygen isotopes can therefore be a proxy of plant cover change and monsoon variation. Our stable isotope results show that lower carbon isotope values of the stalagmites between 200 BC and AD 1000 probably imply dense plant cover and an episode dominated by humid summer monsoon. From ~1000 to AD 1450, the dominant monsoon alternated between the winter monsoon and the summer monsoon. Since ~AD 1450, a significant jump in carbon isotope ratios and increasing oxygen isotope ratios has been demonstrated, indicating less plant cover and the probable dominance of dry winter monsoon. The results are consistent with historical documents of the region.     

台闽北部地区海岸阶地之对比

针对台湾海峡东岸台湾北部的海岸阶地进行调查研究,并与西岸福建东北部的海岸阶地进行分析比较;着重阐述台湾西北部4个海岸区域阶地的特性(阶序、分布、高度、崖差、构成等)及其变动情况(阶地抬升、变窄、延伸等);通过推断形成年代、测算隆升速率等,探讨研究区域的海岸线变化与构造升降运动,结果发现:台湾岛的海阶变化不仅受到海平面变动的影响,尚受到区域性地壳隆升的控制;福建沿海地区受蓬莱造山运动的影响极小,海岸阶地的形成主要是受到数次海平面变化的影响;福建沿海的隆升速率由北向南逐渐减少,总体上低于海峡东岸台湾岛的隆升率(平均2 mm/a).该研究印证了:相对于台湾岛地区,福建沿海地区的地壳活动相对稳定,其海阶发育可能仅受到海平面变动的影响.