1998年4-5月地球同步轨道MeV电子通量增强事件

采用GOES9卫星观测的能量大于2MeV和大于4MeV电子通量和行星际飞船ACE太阳风参数的高时间分辨率资料,以及磁暴指数Dst资料,分析了1998年4-5月期间地球同步轨道电子通量增强事件的时间和能量响应特征及其与行星际太阳风参数、磁暴和亚暴等扰动条件的对应关系.结果表明,地球同步轨道相对论性（MeV）电子通量增强事件有明显的周日变化,中午极大和午夜极小.4月22日和5月5日开始的两次大事件中,能量大于2MeV电子通量中午极大值上升到最大值的时间尺度分别约为4天和1天,中午极大值高于背景水平的持续时间分别为13天（4月22日-5月4日）和16天（5月4日-20日）以上.每次MeV电子通量增强事件的能量范围不完全相同.两次大事件的上升段都对应于磁暴的恢复相,与太阳风动压脉冲、高速流脉冲和负Bz分量关系密切.     

井间电磁成像系统应用研究

井间电磁（EM）成像系统的技术目标是实现井间电学特性的直接测量,并提供井间电阻率的二维及三维图像.从1997年开始,胜利油田与美国EMI公司合作,开展了EM技术的应用与研究,主要是通过大型、系统的现场试验,在大井间距的条件下,进一步验证仪器的性能,进行油藏研究的适用性和可行性分析;以系统的现场实测数据为依据,加快成像处理方法和软件的开发;开展穿透金属套管井的EM试验,探讨金属套管条件下的电阻率成像方法。两年来,利用EMI提供的XBH2000型测量系统,对胜利油田典型的低电阻率砂泥岩剖面,成功地进行了3对井、10个井次的试验。试验证明了仪器性能的可靠,取得了测量重复性好、系统完整的井间EM数据.并反演得到电阻率成像,在分析井间油气分布和油层开采动态方面,取得了良好的地质效果.     

Changes in velocity profiles at roughness transitions in coarse grained channels

Heterogeneous coarse grained channels are often characterized by local transitions in bed surface roughness. Distinct spatial zones in terms of grain size have been reported, for example sand ribbons and bedload sheets. The transition from areas of finer to coarser grained surface sediment is often abrupt. However, the effects of these transitions on the shape of the velocity profile and associated shear velocity and roughness length estimates have not been investigated in detail in coarse grained channels. This paper therefore examines the combined effects of a sudden change in surface roughness and of superimposed scales of resistancé on the structure of the turbulent boundary layer. Measurements along roughness transitions from smooth to rough beds were conducted in a flume using artificial roughness features and in a natural gravel bed river. Immediately at the transition from a zone of close packed roughness to a rougher section dominated by obstacles superimposed on the more or less uniform roughness surface, boundary shear stress and roughness length increase considerably. Downstream from this transition, velocity profiles become concave upwards. Downstream and upstream sections show significant differences in terms of near bed velocities (deceleration downstream of the transition), velocity gradient and turbulence intensity of the streamwise velocity component. Comparing the mean velocity profiles corresponding to these two different roughness surfaces gives some indication of the proportion of total shear velocity (or shear stress) associated with the pressure drag produced by large and isolated obstacles.     

ON SOME NEOLITHIC (AND POSSIBLY PALAEOLITHIC) FINDS IN MONGOLIA,SINKIANG AND WEST CHINA

In the course of the past two years,when they were in the field with theThird American (1930) and the Haardt-Citroen (1931) Central Asiatic Expedi-tions,the authors of the present note had opportunities for making a series ofarchaeological observations ov     

ON AN ENIGMATIC PTEROPOD-LIKE FOSSIL FROM THE LOWER CAMBRIAN OF SOUTHERN SHANSI,BICONULITES GRABAUI,NOV.GEN.,NOV.SP.

Ⅰ. GEOLOGY OF THE SITE The Lower Cambrian fossils here described were first found, insufficiently preserved, by Licent and Teilhard in 1926 at K(?)ntingshih (圪丁石), just along the border of the high limestone range, 50 lis N. of Cbishanhsien (S. Shansi).     

ON THE RECENT MARINE BEDS,AND THE UNDERLYING FRESHWATER DEPOSITS,IN TIENTSIN By E.LICENT AND P.TEILHARD DE CHARDIN

Marine beds, containing numerous well preserved shells, are actuallyexposed in a broad pit recently open, one mile south from the Hoangho-PaihoMuseum (Race Course Road, Tientsin), in order to get the earth required forthe filling of some pools along the Race Course Road.     

THEME 5 SEDIMENT PROBLEMS RELATED TO INTAKE STRUCTURES AND THE INFLUENCE OF INTAKES ON THE SEDIMENT REGIME OF RIVERS

ABSTRACT

The paper presents the observed effects on the streamflow of changing a tropical forest in the high rainfall belt of Zambia to agricultural use based on traditional farming methods. Hydrological observations were carried out on four small catchments under their natural conditions first, and later two of them under agricultural use with accompanying deforestation. Simple linear regression analysis of both monthly and annual runoff from the treated catchments on the monthly and annual runoff from undisturbed catchments showed that there was an increase in streamflow as a result of deforestation and subsistence agriculture. It is also shown that the shape of the flood hydrograph was changed as a result of changes in land use.     

Interpretation of the behaviour of agrowell systems in Sri Lanka using radial flow models

Abstract

This paper describes a study of the use of large diameter “agrowells” used for irrigation in Sri Lanka. Detailed field information for a single location is presented and a numerical radial flow model was used to interpret the field response. Initially the model was used to represent a pumping test in which the pumping and subsequent recovery were monitored. It was then used to investigate the operation of the well during a dry season. Satisfactory agreement could only be obtained when account was taken of the withdrawal of water from below the water table by trees. From the simulation it was possible to show that skilful farming practice could be used in steadily exploiting the resources for irrigation over the whole of the dry season.