泥石流沟谷演化的不等时距灰色预测*

泥石流沟谷纵剖面形态系表征泥石流发育的综合地形指标.本文以利子依达沟为例,用不等时距GM(1,1)预测沟谷纵剖面形态指数N值的变化,并改进了预测模型的精度.     

Models of deep electrical conductivity obtained from data on global magnetic variational sounding

An analysis of published papers containing magnetovariation sounding data (MVS) is carried out. A catalogue of the most trustworthy MVS parameters' values covering periods from 6 hours up to 11 years is compiled. With the help of averaged data of the magnetovariation sounding a planetary geoelectric profile is constructed meeting the requirements of up-to-date understanding of the physical processes in the Earth.     

Rates of erosion of till in the nearshore zone

Measurements of vertical erosion of till in water depths ranging from 1.1 m to 5 m have been obtained using a modified micro-erosion meter. Measurements in this environment are hindered by poor underwater visibility and losses due to high erosion rates and ice action. There is considerable spatial and temporal variability in the erosion rates measured but average values show a general increase from 11 mm y^?1 in 6 m of water to about 35 mm y^?1 in 2.3 m of water and even higher rates closer to shore. The measured values in shallow water are in good agreement with long-term rates extrapolated from shoreline recession. It is suggested that erosion occurs through abrasion and fluid stressing, and that these mechanisms are aided by softening of the upper surface of the till, possibly through cyclic ‘fatigue failure’.     

"中国地学大断面与深部地球物理资料整理"项目成果介绍

本文详细介绍了“中国地学大断面与深部地球物理资料整理”项目的立项背景、目标、所开展的主要工作、取得的成果、研究成果的社会效益和对该领域研究未来工作的展望。     

Intertidal subsidence and collapse features on wave‐exposed,drift‐aligned sandy beaches subject to Amazon mud: Cayenne,French Guiana

Short‐lived collapse features affecting the intertidal sandy profile were observed on mud‐rich beaches in Cayenne. They were formed in packets of beach sand accumulating over thick (several metres) fluid to under‐consolidated foreshore mud, which adjusts to this sand loading by seaward and longshore migration of fluid mud and subsequent in situ mud dewatering, thus generating subsidence and deformation of the overlying sand sheet. These sandy collapse features required active longshore sand transport and were washed out by wave processes at each rising tide. They finally disappeared permanently as adjustment of the underlying mud enabled stabilization of the beach profile. Copyright © 2006 John Wiley & Sons, Ltd.     

热释光法在内蒙东胜地区铀矿找矿中的试验应用

土壤天然热释光测量是一种穿透能力较强的核技术方法,能探测到地下较深处的地球物理信息。简单介绍了土壤天然热释光方法测量原理,研究了土壤热释光测量的影响因素。通过对已知剖面测量的结果表明,土壤天然热释光法在寻找铀矿床上可取得较好的效果。     

压制截断效应的Radon变换在波场分离中的应用

由于离散运算,Radon变换方法中存在截断效应,传统的最小二乘约束反演并不能有效抑制这种效应。介绍了一种频域空间稀疏约束算法,在反演迭代过程中,根据前一次迭代的结果,通过贝叶斯原理将加权矩阵与前一次迭代的结果联系起来,得到新的加权矩阵;然后求解这个加权矩阵方程,得到频率域的稀疏解。比较了用最小二乘反演和压制截断效应的Radon域变换的效果,后者效果明显优于前者。模拟了一个5层的水平地层的地质模型,用这种压制截断效应的Radon变换进行了VSP资料的上下行波场的分离,得到了较好的效果。     

Velocity and concentration profiles of particle movement in sheet flows

Sheet flows occur widely in natural free-surface flows including rivers in flood, tidal estuaries and coastal waters in storm conditions when bed shear stress becomes sufficiently high. Particle volumetric concentration in sheet flows normally follows a linear distribution with the Rouse [Rouse H. Modern conceptions of the mechanics of fluid turbulence. Trans ASCE, 1937;102:463–543] distribution applicable in the dilute water column above the sheet-flow layer. However, a well-verified formula for determining particle velocity distribution in sheet flows is still lacking. This paper presents formulas to describe the particle velocity profile in steady or oscillatory sheet flows. They compare well with measured data. In particular, the novel formula for determining the particle velocity at the top of bedload–sediment-dominated sublayer in sheet flows is also well verified with measured data.     

Hypothesis of the multiple subsidence trough related to very steep and vertical coal seams and its prediction through profile functions

Coalfields in the north of Spain (Asturias) are mainly steeply dipping and at considerable depth. There is widespread use of caving mining methods at the present time. This paper describes a theory developed to predict the subsidence related to very steep and nearly vertical coal seams (70°–90°). This theory of the multiple subsidence trough is applied through a new profile function. Three real cases are analysed and the profile function is adjusted. An empirical relationship between the parameters of the new profile function and geological and mining factors has been developed.