液态水含量和冰晶浓度对闪电频数影响的数值模拟研究   总被引：4，自引：1，他引：4  

谢屹然  郄秀书  郭凤霞  Marcia Baker 《高原气象》2005,24(4):598-603

假定在软雹和冰晶碰撞的非感应起电机制为主要的起电机制成立的条件下，数值模拟研究了国际上公认的Fletcher和H—M冰晶产生机制以及云中的液态水含量对雷暴云放电过程（区分了云闪和地闪）的影响。结果表明，随着气压和温度的变化，在两种冰晶产生机制假定下，冰晶浓度分布有很大差异，这直接导致了雷暴云内电活动的差异。液态水含量的增加将使得首次放电时间延迟，同时将引起放电位置的下降和闪电频数的减少。  相似文献   

Predicting grain protein content of winter wheat using remote sensing data based on nitrogen status and water stress     

《International Journal of Applied Earth Observation and Geoinformation》2005,7(1):1-9

Advanced site-specific knowledge of grain protein content of winter wheat from remote sensing data would provide opportunities to manage grain harvest differently, and to maximize output by adjusting input in fields. In this study, remote sensing data were utilized to predict grain protein content. Firstly, the leaf nitrogen content at winter wheat anthesis stage was proved to be significantly correlated with grain protein content (R² = 0.36), and spectral indices significantly correlated to leaf nitrogen content at anthesis stage were potential indicators for grain protein content. The vegetation index, VI_green, derived from the canopy spectral reflectance at green and red bands, was significantly correlated to the leaf nitrogen content at anthesis stage, and also highly significantly correlated to the final grain protein content (R² = 0.46). Secondly, the external conditions, such as irrigation, fertilization and temperature, had important influence on grain quality. Water stress at grain filling stage can increase grain protein content, and leaf water content is closely related to irrigation levels, therefore, the spectral indices correlated to leaf water content can be potential indicators for grain protein content. The spectral reflectance of TM channel 5 derived from canopy spectra or image data at grain filling stage was all significantly correlated to grain protein content (R² = 0.31 and 0.37, respectively). Finally, not only this study proved the feasibility of using remote sensing data to predict grain protein content, but it also provided a tentative prediction of the grain protein content in Beijing area using the reflectance image of TM channel 5.  相似文献   

The effect of rock moisture on Schmidt hammer rebound: tests on rock samples from Marion Island and South Africa     

Paul Sumner  Werner Nel 《地球表面变化过程与地形》2002,27(10):1137-1142

In an assessment of the influence of internal rock moisture content on Schmidt hammer readings, rebound (R) values are found to decrease with increasing moisture content. For samples of basalt, sandstone and dolerite the maximum decrease in R‐values is found between oven dry values and saturated rock rebound values, the magnitude of which varies from 2 to 10 points on the R‐scale. A quartzite block has the greatest decline of 6 points at 60 per cent saturation. For certain rock types under differing site‐to‐site field moisture conditions the moisture effect can be a significant factor in the interpretation of the relative state of weathering from rebound values. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Sulfur Content and Isotopic Ratio of Cambro-Ordovician Carbonate Rocks from South Korea: A Possible Source for Mesozoic Magmatic-hydrothermal Ore Sulfur     

Shunso ISHIHARA  Myung–Shik JIN  Yoshimichi KAJIWARA 《Resource Geology》2002,52(1):41-48

Abstract: Carbonate rocks of Cambrian (18 samples) and lower-middle Ordovician (11 samples) ages from South Korea were analyzed for sulfur contents of structurally substituted sulfate (SSS) and sulfides and their δ³⁴S values. The δ³⁴S values of SSS ranging from +25.9 to +45.2 permil, are averaged as +33.6 and +33.5 permil for the Cambrian and Ordovician rocks, respectively, which indicate high δ³⁴S values of the Cambro-Ordovician seawater. The SSS contents in the carbonate rocks are low being 2.9 to 17.3 ppm S (averaged as 7.0 ppm S). Sulfide sulfur, on the contrary, is much abundant containing 3 to 1,880 ppm S and the δ³⁴S values range widely between –17.6 and +31.1 permil. Sulfide sulfur of the studied rocks excluding impure carbonates has an average content of 187 ppm S and δ³⁴S value of +12.8 permil (n=24). The estimated δ³⁴S (sulfate–sulfide) values, which range from 13.8 to 25.4 permil in general with a few exceptions from 36.5 up to 52.3 permil for some impure carbonates, may provide evidence for the persistent oceanic anoxia with its temporary recovery during the Cambro-Ordovician time.
The SSS and sulfide sulfurs have often higher δ³⁴S values than the Mesozoic-Cenozoic ore sulfur (Ishihara et al., 2000). Since carbonate rocks are very reactive with circulating hydrothermal ore solution, high δ³⁴S values of the Korean ore deposits might be caused to some extent by ³⁴S enrichment from the host carbonates, resulting in the low SSS contents observed.  相似文献   

Study on Paleoenvironment since Late Glacial Eooch in Lanzhou Area, China     

Yang Guifang  Yin Hongfu  Li ChangAn 《中国地质大学学报(英文版)》2002,13(1)

The Hongzuisi Section in Lanzhou area is used to infer the paleoclimate since the late glacial epoch. Through combined analysis of organic carbon isotope and CaCO3 content, paleoenvironment evolution of Hongzuisi Section since the late glacial epoch is discussed. There were changes in both drymoist and warm-cold. Especially the climate changes can be compared with synchronous sections of other areas, which provides useful information for our future forecast.  相似文献   

云南水汞在姚安6.5级地震前的异常特征分析     

杨杰英 《高原地震》2002,14(4):36-41

对2000年1月15日姚安6．5级地震前后云南水汞异常进行分析研究，结果表明：在9个观测台站中，地震前有1个观测台站的水汞出现中期趋势异常，1个台站的水汞出现远震异常，4个台站的水汞出现短期异常，1个台站的水汞出现临震异常。地震前3个月内，水汞短期异常有活跃，平静的过程，在平静中(仅1个台站出现临震异常)发生姚安6．5级地震。姚安地震发生在距出现远震异常的水汞观测台站70km的地方。出现远震异常的水汞观测台站附近，可能是未来强震的发震地区。  相似文献   

Simultaneous radio and optical observations of the mid-latitude atmospheric response to a major geomagnetic storm of 6–8 April 2000     

E. L. Afraimovich  Ya. F. Ashkaliev  V. M. Aushev  A. B. Beletsky  V. V. Vodyannikov  L. A. Leonovich  O. S. Lesyuta  Yu. V. Lipko  A. V. Mikhalev  A. F. Yakovets 《Journal of Atmospheric and Solar》2002,64(18)

Basic properties of the mid-latitude traveling ionospheric disturbances (TIDs) during the maximum phase of a major magnetic storm of 6–8 April 2000 are shown. Total electron content (TEC) variations were studied by using data from GPS receivers located in Russia and Central Asia. The nightglow response to this storm at mesopause and termospheric altitudes was also measured by optical instruments FENIX located at the observatory of the Institute of Solar-Terrestrial Physics (51.9°N,103.0°E), and MORTI located at the observatory of the Institute of Ionosphere (43.2°N, 77.0°E). Observations of the O (557.7 and 630.0 nm) emissions originating from atmospheric layers centered at altitudes of 90 and 250 km were carried out at Irkutsk and of the O₂(b¹∑_g⁺−X³∑_g⁻) (0-1) emission originating from an atmospheric layer centered at altitude of 94 km was carried out at Almaty. Our radio and optical measurement network observed a storm-induced solitary large-scale wave with duration of 1 h and a wave front width of no less than 5000 km, while it traveled equatorward with a velocity of 200 m/s from 62°N to 38°N geographic latitude. The TEC disturbance, basically displaying an electron content depression in the maximum of the F2 region, reveals a good correlation with growing nightglow emission, the temporal shift between the TEC and emission variation maxima being different for different altitudes. A comparison of the auroral oval parameters with dynamic spectra of TEC variations and optical 630 nm emissions in the frequency range 0.4–4 mHz (250–2500 s periods) showed that as the auroral oval expands into mid-latitudes, also does the region with a developed medium-sale and small-scale TEC structure.  相似文献   

乌鲁木齐10号泉He含量变化的映震特征   总被引：5，自引：0，他引：5  

高小其  蓝陵  许秋龙  李新勇  崔勇  李艳萍  迪里夏提 《四川地震》2002,(3):27-31

本文从监测泉点的水文地质概况入手，结合近19年来的资料分析了10号泉水中氦含量变化的映震特征：氦含量变化的地震前兆异常基本上都是正异常，且具有较好的重复性，泉点即流量测值遵循：背景值一趋势性上升（或突升）－最高值－趋势性下降（或突降）－恢复至背景值的变化过程。而地震常常发生在氦含量由高变低的过程中。最后初步认定了泉点较好的地质构造环境和氦特有的化学特性是该泉氦具有映震灵敏性的原因。  相似文献   

数字城市建设研究   总被引：7，自引：0，他引：7  

段学军 《地域研究与开发》2003,22(5):1-4

数字城市建设是一项复杂的系统工程，需要做好规划，解决管理、制度、标准以及必须的关键技术等问题。文章在分析了数字城市建设目标和内容的基础上，探讨了数字城市建设的基本原则，提出了数字城市建设的具体实施方案。  相似文献   

Sensitivity Analysis of a Feedforward Neural Network for Considering Genetic Mechanisms of Kuroko Deposits     

Matsuda  Setsuro  Koike  Katsuaki 《Natural Resources Research》2003,12(4):291-301

Exploration for volcanogenic massive sulfide deposits of the kuroko-type is underway in many places. Clarifying the spatial patterns of the metals in kuroko deposits will be useful for understanding their genetic mechanisms and for future exploration of such types of deposits. This study represents a spatial distribution analysis on the contents of principal metals of kuroko deposits: Cu, Pb, and Zn, in the Hokuroku district, northern Japan, by a feedforward neural network and 1917 sample data at 143 drillhole sites. The network, which consists of three layers, was trained by the principle of SLANS in which the numbers of neurons in the middle layer and training data are changed to improve estimation accuracy. Using the weight coefficients connecting adjacent neurons, sensitivity analysis of the neural network was carried out to identify factors influencing spatial distributions of the three metals. The coordinates depth (z) direction, Bouguer gravity, and specific lithology such as dacite were determined to be influencing factors. The high frequency of the z coordinate signifies that the metal contents differ to a large extent by depth. The sensitivity vector was defined using sensitivity coefficients for x, y, and z coordinates of an estimation point. We determined that the directions of large vectors were different inside and outside of the Hanawa-Ohdate area. This characteristic is considered to originate from the differences in the permeability of fractures that became the paths for rising ore solutions, and the depths that the solutions mixed with sea water.  相似文献