扬子地台钾镁煌斑岩 Nd、Sr、Pb 同位素特征

扬子地台周缘钾镁煌斑岩 Nd、Sr同位素特征介于南非Ⅰ、Ⅱ型金伯利岩和西澳与北美钾镁煌斑岩两种变化趋势之间，不同岩区间同位素组成差异反映地台周边构造性质不同，Pb同位素特征表明晚太古代地幔岩石圈具U亏损特征。     

Typical basin-fill sequences and basin migration in Yanshan, North China--Response to Mesozoic tectonic transition

Basin-fill sequences of Mesozoic typical basins in the Yanshan area, North China may be divided into four phases, reflecting lithosphere tectonic evolution from flexure (T3), flexure with weak rifting (J1+2), tectonic transition (J3), and rifting (K). Except the first phase, the other three phases all start with lava and volcaniclastic rocks, and end with thick coarse clastic rocks and/or conglomerates, showing cyclic basin development rather than simple cyclic rift mechanism and disciplinary basin-stress change from extension to compression in each phase. Prototype basin analysis, based on basin-fill sequences, paleocurrent distribution and depositional systems, shows that single basin-strike and structural-line direction controlling basin development had evidently changed from east-west to northeast in Late Jurassic in the Yanshan area, although basin group still occurred in east-west zonal distribution. Till Early Cretaceous, main structural-line strike controlling basins just turned to northeast by north in the studied area.     

Study of charge structure and radiation characteristic of intracloud discharge in thunderstorms of Qinghai-Tibet Plateau

The comprehensive observations on lightning discharges were conducted in Naqu area of Qinghai-Tibet Plateau in summer of 2002. The electric structures of thunderstorms and the characteristics of lightning discharges at initial stage were analyzed by using the observation data. The results show that most of intracloud (IC) lightning flashes were polarities inverted in thunderstorms with tripole electric charge structure and occurred between negative charge region located in the middle of the thunderstorm and positive charge region located at the bottom of the thunderstorm. The radiation characteristics of discharge processes in cloud with longer lasting time involved in Cloud-to-Ground (CG) lightning flashes were similar to that of IC discharges.A lot of radiation pulses were produced in these discharge processes. Because the IC discharges took place at the bottom of thundercloud and were near the ground, they may produce more serious damage to equipment on the ground therefore should not be neglected in lightning protection.     

Development of joints and shear fractures in the Kuqa depression and its implication to regional stress field switching

The superimposed basin must have undergone the changes of regional stress field. Study on the nature and switch of regional stress field of superimposed basin is very useful to understanding its stress state and tectonic events during its formation and evolution. As sensitive markers of small stress changes, joint and shear fracture, characterized by consistency of orientation over wide area, can be used to reconstruct paleostress state and its evolution. Detailed observations and analysis on the orientations, geometrical patterns, sequences of joints and shear fractures and their chronological relation to faults and folds show that, the NEE-SWW systematic joints and NNW-SSE systematic joints developed in the Mesozoic and Cenozoic strata are much more prominent than NW-SE systematic joints and shear fractures with different orientations. And the NWW-SEE and NW-SE systematic joints formed later than NEE-SWW systematic joints but earlier than shear fractures with different orientations. According to the relationships between joint and shear fractures and stress, the NEE-SWW systematic joints are inferred to result from lateral weak extension caused by the late Cretaceous regional uplift, while the NNW-SSE and NW-SE systematic joints are interpreted as syn-tectonic deformation relating to strong N-S compression in the Neogene. But some conjugate shear fractures occur probably due to sinistral strike-slip faulting in the Kuqa depression. At the beginning of the Neogene, the stress field changed and the maximal principal stress σ1 switched from vertical to horizontal.     

Sedimentary environment and development controls of the hydrocarbon source beds:Middle and Upper Proterozoic in northern North China

Problem on development control of marine source bed hold in Chinese petroleum industry progression. The Hongshuizhuang Formation,Tieling Formation and Xiamaling Formation in the Middle and Upper Proterozoic are important hydrocarbon source beds in northern North China, and investigation of their sedimentary environments and the controls has great significance for petroleum exploration in North China. Based on sedimentology (sequence stratigraphy), palaeoecology, sedimentary geochemistry, and sedimentary palaeogeography, their development pattern is discussed. All these studies indicate that the development controls of the hydrocarbon source beds include a favorite palaeogeographic location, exceeding propagation of biomes in low and middle latitudes, anoxic environments, enrichment of phosphorus element and the adsorption of clay minerals during the preservation of organic matter in the marine carbonates.     

A Case study of a snowstorm at the Great Wall Station,Antarctica

A case of a snowstorm at the Great Wall Station was studied using data of NCEP (National Centers for Environmental Prediction) analysis, in situ observations and surface weather charts. The storm occurred on August 29th,2006, and brought high winds and poor horizontal visibility to the region.It was found that the storm occurred under the synoptic situation of a high in the south and a low in the north. A low-level easterly jet from the Antarctic continent significantly decreased the air temperature and humidity.Warm air advection at high level brought sufficient vapor from lower latitudes for the snowstorm to develop.The dynamic factors relating to strong snowfall and even the developmentof a snowstorm were deep cyclonic vorticity at middle and low levels,the configuration of divergence at high level and convergence at low level, and strong verticaluplift. There was an inversion layer in the low-level atmosphere during the later phase of the storm.This vertical structure of cold air at low levels and warm air at high levels may have been important to the longevity of the snowstorm.     

巧用CASIO fx-4800P计算器测设线路复合曲线

应用地面点与线路中线相对关系的统一数学模型，使用CASIO fx-4800P程序型计算器编制的适合野外测设线路各种复合曲线(包括直线、缓和曲线、圆曲线的任意组合)的实用程序。     

Design of an adaptive GPS vector tracking loop with the detection and isolation of contaminated channels

GPS Solutions - In vector tracking loop (VTL), the relativity among received signals is exploited to deeply integrate the entire information within signal processing channels. However, the tracking...     

Soil moisture dynamics under different land uses on karst hillslope in northwest Guangxi,China

Temporal and spatial dynamics of soil moisture are little known on karst hillslope with shallow soil in subtropical region. The objectives of this paper were (1) to investigate the temporal dynamics of soil moisture at depth of 0–10 cm under different land uses; and (2) to understand the relationship between mean and coefficient of variation (CV) of moisture contents on karst hillslope in northwest Guangxi, China. Soil moisture contents had a moderate variation (CV 17.5–30.3%) over an 8-month period and they had a significant difference among different land uses at the 0.01 level with a decreasing order: native scrubland > abandoned cropland and sloping cropland > economic forestland. There were higher mean and lower CV of moisture contents in rainy season than those in drought season. Mean and CV of moisture contents had a significant negative linear relationship except in abandoned cropland with higher soil and vegetation heterogeneity. This suggested that spatial variability of soil moisture within sampling sites would decrease when soils were wet and increase when soils were arid. Compared with rainy season, more soil samples may be needed and the interval for sampling should be shortened in drought season. Such information provided some insights to better understand the dynamics and variability of soil moisture at a larger scale in karst region of southwest China.     

An approximate analytical solution for measuring air permeability of asphalt samples partially saturated with water

In coastal areas, abnormally high pressure may be caused by the tide-induced water table variation under extensive pavements, particularly during rainfall. To simulate the rainfall infiltration effects on the air permeability of asphalt pavements in coastal area, column-shaped asphalt sample was fixed in the upper part of a steel cylinder with its upper surface saturated with ponding water (depth < 5 mm) and open to the atmosphere. The cylinder’s lower part formed an air chamber. The chamber was pressurized and then the air therein was released naturally through the sample. The pressure variation with time in the chamber was recorded for analysis. Based on the Green–Ampt piston model for the surface water infiltration, an approximate analytical solution was derived to describe the pressure–time relationship in the chamber. A new parameter called the escape pressure was introduced to describe the air pressure needed for the chamber air to break through the capillary pressure induced by the ponding water. The analytical solution gave good estimations of both the escape pressures and the harmonic averages of the permeabilities of the wet and dry parts of 14 samples in the sense that excellent fittings were obtained between the observed and predicted air pressures in the air chamber. The estimated escape pressure ranges from 0.0 to 1.74 kPa. The harmonic average of the permeabilities of the wet and dry parts is 5–94% of the dry sample’s permeability.