Measurements of level-crossing statistics of concentration fluctuations in plumes dispersing in the atmospheric surface layer     

Eugene Yee  R. Chan  P. R. Kosteniuk  G. M. Chandler  C. A. Biltoft  J. F. Bowers 《Boundary-Layer Meteorology》1995,73(1-2):53-90

The statistics of level crossings and local extremes in concentration fluctuations in plumes dispersing in the atmosphere have been investigated. A set of concentration fluctuation tracer experiments has been utilized to measure the statistical propertics of the upcrossing interval (inter-arrival time between consecutive concentration bursts), excursion duration (persistence or width of concentration bursts), and concentration amplitude (difference between the maximum and minimum concentrations between successive upcrossings) with respect to a range of concentration crossing levels. In particular, the effect of downwind distance and atmospheric stratification on the level-crossing statistics has been studied in detail. It is shown that the effect of increasing atmospheric stability on level-crossing statistics is similar to the effect of increasing distance from the source in the sense that level-crossing statistics of concentration fluctuations in stable stratification resemble those in neutral stratification, but at a greater downwind distance. It is also found that the distribution of the interval between consecutive upcrossings of a concentration level, as well as the duration of an excursion across a concentration level, can be approximated by a lognormal distribution, whereas the distribution of the concentration amplitude is best characterized by a gamma distribution. Some implications of these results for the modeling of level-crossing statistics of concentration fluctuations are discussed.  相似文献   

The difference in chemical composition of the 1962 lava from miyakezima magma reservoir in Japan     

I. Iwasaki  T. Ozawa  M. Yoshida  T. Katsura  Chan Kuk Kim  M. Aoyagi  Y. Yoshiike 《Bulletin of Volcanology》1982,45(2):81-85

Many examples of mixed magmas in banded lavas have been studied. Another type of mixed magmas or inhomogeneity of magma reservoir found in the 1962 lava flows of Miyake-zima Volcano erupted from fissures is reported.  相似文献   

Pneumatic beneficiation of coal fines using the counter-current fluidized cascade     

E.W. Chan  J.M. Beeckmans 《International Journal of Mineral Processing》1982,9(2):157-165

The counter-current gas-fluidized cascade (CFC) is a novel pneumatic device for separating mixed granular solids according to specific gravity. The possible utility of the CFC for beneficiation of coal in all size-ranges is presently under investigation, and in this paper some results are reported on pyrite beneficiation of synthetic pyrite-coal mixtures, and also on pyrite and ash beneficiation of as-received coal. The (geometric) mean particle size, by weight, of the coal used with added pyrite was 153 μm, and of the natural coal 233 μm. Preliminary results on the concentration of pyrite and ash in the reject streams indicate that CFC has some potential of being a simple and low-cost device for coal beneficiation.  相似文献   

Subliquidus glass-glass immiscibility along the albite-diopside join     

D.J. Henry  I.D.R. Mackinnon  I. Chan  A. Navrotsky 《Geochimica et cosmochimica acta》1983,47(2):277-282

A calorimetric study has shown that glasses along the albite-diopside join in the system albiteanorthite-diopside have positive enthalpies of mixing. Thermodynamic calculations based on these data describe a nearly symmetric, metastable, subliquidus irascibility gap along the join with a critical temperature at 910 K. The existence of the miscibility gap was tested experimentally by annealing an Ab₅₀Di₅₀ glass at 748 K and 823 K. Annealed glasses were examined by optical microscopy and by scanning and transmission electron microscopy. The glasses showed morphological and chemical features consistent with unmixing of two glass phases. The apparent mechanism of phase separation involves initial spinodal decomposition followed by coarsening to produce 0.1 μm–0.3 μm spherical glass phases.  相似文献   

西藏易贡崩塌——滑坡—泥石流的地质地貌与运动学特征   总被引：4，自引：0，他引：4  

任金卫  单新建  沈军  格桑  扎桑  邓桂英  张军  索仁 《地质论评》2001,47(6):642-647

2000年4月9日19时59分18.2秒,在西藏自治区波密县境内易贡乡发生了特大崩塌—滑坡—泥石流。构造上它发生在印度板块阿萨姆楔入角复合地带的西侧,也是高原腹地向东侧山地下降的过渡带,重力作用明显。根据便携式GPS定位仪实地测定和滑坡前后的卫星影像分析,崩塌—滑坡—泥石流堆积物形成了一座长约5.7km、宽约1.5km的“天然大坝”,完全堵塞了易贡藏布河干流,崩塌滑坡体总方量超过3.8×10~8m~3。根据区域地震台网的记录,其振动持续的时间为6min,其中最大振幅的持续时间为2min。震相分析表明有3组较为明显的震相,对应着3次较大的地表振动。计算获得崩塌滚落的平均速度约为48m/s,伴随崩塌滚落的同时,滑坡泥石流的平均滑动速度也达到了16 m/s,比一般泥石流流动速度要大一倍。  相似文献   

固体潮时频分析新方法   总被引：5，自引：2，他引：5  

周挚  山秀明  梁虹  杜爱明  全海燕  张婕  杜昌寿  杨配新  杨胜梅 《地震研究》2005,28(4):334-339

对传统时频分析方法的特点和局限性作了介绍。采用Huang．Hilbert Transformation方法分析了固体潮数据，即利用经验模态分解，将复杂信号分解成有限个本征模态函数之和，求取三维时频空间的Hilbert谱。仿真实验和重力固体潮实例分析表明，该方法适用于调频调幅信号特征的提取。  相似文献   

四川省宁南县主要地质灾害特征及防御对策   总被引：1，自引：0，他引：1  

陈玉禄  苟宁刚  单成德  姚江宁  唐扬贵 《地质灾害与环境保护》2005,16(2):119-124

宁南县属地质灾害频发区。主要地质灾害点共有31处。威胁6757人的生命财产安全。其中对城镇发生直接威胁4处，学校威胁3处，度假山庄威胁1处，潜在经济损失达22765万元。本文在详细论述地质灾害体特征的基础上并提出了相应的防御对策，提出对当地居民构成重大生命财产威胁的共5处，需采取治理措施，以减少地质灾害的发生。  相似文献   

辽东裂谷中的玉石成矿研究     

白永俊  王洪波  单晓刚 《地质找矿论丛》2005,20(Z1):134-138

辽东裂谷内的辽河群南带为玉石成矿有利部位,大石桥组三段为主蕴矿层,其层间断裂为主要的布矿和储矿构造.辽河期黑云二长花岗岩及其脉岩与富镁质碳酸盐岩接触部位对成矿最有利.玉石产于中-高温、高压、SiO2不饱和的封闭型地质环境中,为层控型热液交代为主的复合成因矿床.  相似文献   

基于网络环境的MapMIS数字化生产管理系统   总被引：2，自引：2，他引：2  

单文淼  刘四宁  齐南平  朱云 《测绘科学》2002,27(4):57-60

Map MIS是一个应用于数字化测绘生产的管理信息系统。它集成了网络、数据库、分布式数据仓库技术 ,它可以在生产过程中帮助生产管理人员、质量检查人员、作业人员管理与数字化测绘生产相关的事务流、信息流和海量的数据流。提出了数字化测绘生产管理的新模式  相似文献   

低渗透油藏储层沉积微相研究--以松辽盆地乾安油田高台子油层Ⅶ砂组为例   总被引：6，自引：1，他引：6  

王先明  单玄龙 《世界地质》2002,21(3):251-257

针对低渗透油藏储层的特征，以岩心资料和大量的测井，录井数字化资料为基础，应用沉积微相制图软件系统实现了乾安油田高台子油层Ⅶ砂组低渗透储层的沉积微相自动识别，本区储层沉积微相为水下分流河道，席状砂、远砂坝和水下扇等类型，绘制出VII砂组3个小层的平面沉积微相图，沉积微相的研究对本区主力油层及剩余油分布具有指导意义。  相似文献