黑龙江省团结沟金矿床原生晕分带模式     

林名河 《吉林大学学报(地球科学版)》1992,(1)

研究了火山热液金矿床原生晕成晕元素、成晕性质、分带序列与分带结构。根据露天采场岩石地球化学调查资料建立元素分带序列和轴向分带模型。首先按元素成晕性质与成晕相对时间编排子序列;之后联结三个子序列间空间关系最紧密元素(Cr—K—Au)组成总序列。空间上各单元素晕,包括负晕与正晕,在原生晕总体范围呈现规律性排列:K正晕位于核部;Bi、Mo、W晕重叠其下部;Ag、Au、AS、Sb)晕重叠其上部。Mn负晕套合K正晕处围;Mn正晕镶嵌Mn负晕边部Na晕覆盖整个原生晕。  相似文献   

企业领导自觉抓好安全生产的有效途径          下载免费PDF全文

邢洪春 《探矿工程》1994,(3):57-58

根据近３年的工作实践，在当前转换经营机制、实行市场经济的新形势下，提高企业领导自觉抓好安全生产的有效途径是：完善对企业领导的安全考核办法、进行严格的安全培训、落实安全生产责任制和严格依法管安全。  相似文献   

1991年北京延庆人工引雷实验及分析   总被引：4，自引：1，他引：4       下载免费PDF全文

陈明理  刘新中 《地球物理学报》1994,37(2):167-173

简要地叙述了北京１９９１年夏天利用火箭－导线技术两次引雷成功的结果．两次引雷成功均是在地面电场为正（即正电荷当顶）时触发的．触发时地面电场分别为３．１ｋＶ／ｍ和２．５ｋＶ／ｍ，高度在３００－４００ｍ之间．分析表明，两次火箭引雷均系火箭上升到一定高度时激发上行负流光，然后产生连续对地放正电的过程，无回击发生．简单模式分析表明，中和电量小于１０Ｃ，火箭上升过程导线中电晕电流约为４ｍＡ．  相似文献   

Transcriptomic comparison to identify rapidly evolving genes in Braya humilis     

YuMing Wei  XiaoFei Ma  PengShan Zhao 《寒旱区科学》2018,10(5):428-435

  相似文献   

人工引雷上行正先导传播过程中爆发式磁场脉冲极性反转现象的观测与分析     

郑天雪  陆高鹏  谭涌波  樊艳峰  蒋如斌  张鸿波  刘明远  郄秀书 《大气科学》2018,42(1):124-133

为了进一步理解人工引雷上行正先导的传播过程及相关的爆发式电磁辐射脉冲,本文分析了2014年8月23日山东沾化人工触发闪电实验（SHATLE）中获得的三次上行正先导通道含有明显向下传播过程的个例。结果表明,在初始连续电流阶段观测到的爆发式磁场脉冲极性反转现象与正先导头部发展方向相对于观测位置投影方向的变化密切相关。因此可以推断,爆发式磁场脉冲是由正先导头部较小空间尺度放电过程辐射出的,就本文分析的个例而言,爆发式磁场脉冲辐射源的放电尺度约为2 m,放电强度的最大值达到2.49 kA。爆发式磁场脉冲的辐射机制不同于人工引雷先导始发阶段初始脉冲电流产生的磁场脉冲的辐射机制,可能与正先导通道头部的梯级形式发展过程相关。  相似文献   

激光铅垂仪向上投点在地铁隧道工程中进行联系测量的实践     

高绍伟 《北京测绘》2008,(2):57-60

盾构法地铁隧道施工测量中,提高联系测量对隧道贯通起着决定的作用。本文对地铁施工测量贯通测量的误差来源进行了分配,对二井定向利用激光铅垂仪向上投点方案进行了精度分析,并和钢丝投点法的计算成果进行了比较,提出了激光铅垂仪向上投点法方案措施。  相似文献   

Predictions of future hydrological conditions and contribution of snow and ice melt in total discharge of Shigar River Basin in Central Karakoram, Pakistan     

Javed Hassan  Rijan Bhakta Kayasth  Ahuti Shresth  Iram Bano  Sayed Hammad Ali  Haleem Zaman Magsi 《寒旱区科学》2017,9(6):511-524

The high mountains of Hindu-Kush Karakoram and Himalaya(HKKH) contain a large volume of snow and ice, which are the primary sources of water for the entire mountainous population of HKKH. Thus, knowledge of these available resources is very important in relation to their sustainable use. A Modified Positive Degree Day Model was used to simulate daily discharge with the contribution of snow and ice melt from the Shigar River Basin, Central Karakoram, Pakistan. The basin covers an area of 6,921 km2 with an elevation range of 2,204 to 8,611 m a.s.l.. Forty percent of the total area is glaciated among which 20% is covered by debris and remaining 80% by clean ice and permanent snow. To simulate daily discharge, the entire basin was divided into 26 altitude belts. Remotely sensed land cover types are derived by classifying Landsat images of 2009. Daily temperature and precipitation from Skardu meteorological station is used to calibrate the glacio-hydrological model as an input variable after correlating data with the Shigar station data(r=0.88). Local temperature lapse rate of 0.0075 °C/m is used. 2 °C critical temperature is used to separate rain and snow from precipitation. The model is calibrated for 1988~1991 and validated for 1992~1997. The model shows a good Nash-Sutcliffe efficiency and volume difference in calibration(0.86% and 0.90%) and validation(0.78% and 6.85%). Contribution of snow and ice melt in discharge is 32.37% in calibration period and 33.01% is validation period. The model is also used to predict future hydrological regime up to 2099 by using CORDEX South Asia RCM considering RCP4.5 and RCP8.5 climate scenarios.Predicted future snow and ice melt contributions in both RCP4.5 and RCP8.5 are 36% and 37%, respectively. Temperature seems to be more sensitive as compared to other input variables, which is why the contribution of snow and ice in discharge varies significantly throughout the whole century.  相似文献   

基于MEMLS模型的积雪深度反演方法     

李震  邵雨阳  周建民  田邦森  陈权  张平 《遥感学报》2013,17(3):657-670

利用被动微波遥感反演积雪深度一直是积雪遥感领域中的研究热点。在现有的积雪深度反演算法中,NASA算法因其简洁、易于扩展的特点,成为应用最为广泛的算法。但NASA算法存在着一定不足:首先,由于NASA算法基于线性拟合得出,在应用到其他研究区域时需要对反演公式进行重新拟合,适用范围受到一定限制;其次,由于算法中引入的19GHz与37GHz的亮温差在雪深达到一定范围时会达到饱和,因此算法会低估积雪深度。本文针对现有反演算法的不足之处,结合蚁群智能算法的特点,发展了基于蚁群算法的积雪深度反演算法;此外,针对NASA算法中存在的雪深低估问题,引入了AMSR-E10.7GHz亮温数据,对算法进行了改进。利用MEMLS模型的模拟数据与AMSR-E辐射亮温数据对算法进行实验,并采用实测数据与AMSR-E雪水当量产品对算法的反演精度进行评价。结果表明,两种积雪深度反演算法均是可行的,反演精度与现有产品相比有较为明显的改进。  相似文献   

Variation in low food access areas due to data source inaccuracies     

《Applied geography (Sevenoaks, England)》2013

Several spatial measures of community food access identifying so called “food deserts” have been developed based on geospatial information and commercially-available, secondary data listings of food retail outlets. It is not known how data inaccuracies influence the designation of Census tracts as areas of low access. This study replicated the U.S. Department of Agriculture Economic Research Service (USDA ERS) food desert measure and the Centers for Disease Control and Prevention (CDC) non-healthier food retail tract measure in two secondary data sources (InfoUSA and Dun & Bradstreet) and reference data from an eight-county field census covering 169 Census tracts in South Carolina. For the USDA ERS food deserts measure accuracy statistics for secondary data sources were 94% concordance, 50–65% sensitivity, and 60–64% positive predictive value (PPV). Based on the CDC non-healthier food retail tracts both secondary data demonstrated 88–91% concordance, 80–86% sensitivity and 78–82% PPV. While inaccuracies in secondary data sources used to identify low food access areas may be acceptable for large-scale surveillance, verification with field work is advisable for local community efforts aimed at identifying and improving food access.  相似文献   

A cellular automata model for simulating the evolution of positive–negative terrains in a small loess watershed     

Min Cao  Fang Zhang  Jianyi Yang 《International journal of geographical information science》2013,27(7):1349-1363

Cellular automata (CA) have been used increasingly to simulate complex geographical phenomena. This paper proposes a CA model for simulating the evolution of dynamic positive and negative (P–N) terrains in a small loess watershed. The CA model involves a large number of attributes, including the state of P–N terrains, distance to the shoulder-line, neighbourhood condition and topographic factors. Topographic factors include the slope gradient, aspect, slope length, slope variation, aspect variation, plan curvature, profile curvature, relief amplitude and flow accumulation. The CA model was applied to simulate the evolution of P–N terrains in an indoor, small loess watershed under artificial rainfall. The transition rules for CA were constructed automatically using a decision-tree algorithm. The derived transition rules are explicit for decision-makers and helpful for generating more reliable terrains. The simulation produces encouraging results in terms of numeric accuracy and spatial distribution, in agreement with natural P–N terrains. The iterative processes show that loess negative terrains continuously erode positive terrains. The development of a loess sinkhole near the centre gully head was reproduced as well, which shows the function of loess sinkholes in the formation of loess channel systems.  相似文献