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101.
复杂地质条件下气层的多参数识别 总被引:1,自引:0,他引:1
在复杂地质条件下,应用单一或两种孔隙测井资料直接识别气层,灵敏度不高,为了准确地识别复杂地质条件下的气层,需从不同角度,应用多参数进行综合识别,本文介绍了声波法,中子-密度法,双孔隙度法,中子-伽玛法,等效弹性模量法等,并应用它们对哈盆地两口井进行了重点分析,效果良好。 相似文献
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1987~1995年对降水、黑河水和古日乃草原地下水作了定位观测,在巴丹吉林沙漠水文探险中采集了沙漠和戈壁地下水及湖水.降水同位素组成δD~δ18O与Craig线相同,但发现了地下水的δD~δ18D关系平行于降水线且有氘盈余为负且达-22‰的异常,其成因不明.由地表、地下水环境同位素组成,分析了黑河治理规划实施后可能对地下水资源产生的工程影响,它近期不会成为古日乃草原沙漠化进程的因素,但对额济纳绿洲的影响却不容忽视. 相似文献
104.
一次飑线过程中龙卷及飑锋生成的中尺度分析 总被引:11,自引:0,他引:11
对1983年9月4日发生在陕西中部一次灾害性强风暴过程的天气形势、雷达回波、卫星云图、地面中尺度风场资料及灾情进行了综合分析研究,结果表明:此次灾害性强风暴是一次龙卷过程;龙卷出现在冷锋飑线带状回波尾部,呈典型的弓状回波(环状回波);在卫星云图上表现为南北云系交绥处发展旺盛的中尺度涡旋云团,呈新月状;龙卷发生在地面“人”字形辐合线交点后部强西北风中;龙卷是由地面两条冷锋的共同作用造成的;飑锋回波出现在龙卷雷暴后部,表现为两条平行的线状回波,与经典理论有不同之处。 相似文献
105.
Mission to asteroids and comets has been the hot spot of deep space exploration in the new century. The choice of a suitable target, which involves both scientific value and technical feasibility, becomes a difficult task to accomplish due to limited energy and technology. The aim of this paper is to provide an approach to selecting a target and evaluating accessibility for rendezvous with a Near-Earth Asteroid mission, taking into account scientific value and engineering feasibility. Firstly, according to the orbital characteristics and physical properties of Near-Earth asteroids, we make a summary of some of the most frequent factors influencing the target selection of scientific significance. When selecting the target for a space mission, these factors can be regarded as the scientific motivations. Then in order to avoid the possibility that some high priority targets for science would be discarded due to requiring too high an energy budget by using a classical direct transfer strategy, we calculate the transfer trajectory for rendezvous with candidates by using the planetary swingby technique and the global optimal two-impulse method. Finally, through a comparison between the scientific relevance of each possible target and the corresponding estimate of energy needed for rendezvous missions, the ranking of some candidates is identified. 相似文献
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The effects of four microalgae,Chlorella vulgaris,Platymonas helgolandicavar,Isochrysis galbana,and Nitzschia closterium on the grazing and filtering rates of the marine rotifer,Brachionus plicatilis,were evaluated under laboratory conditions.The grazing rates in separate cultures of the four microalga were as follows:C.vulgaris > P.helgolandicavar > I.galbana > N.closterium.However,the filtering rates occurred in the following order:P.helgolandicavar > N.closterium > C.vulgaris > I.galbana.A mixed diets ex... 相似文献
109.
Analysis of types and changes of village-level economy in rural Gongyi city,Henan Province since 1990 总被引:1,自引:1,他引:0
Based on the research on the rural living standard in China in terms of annual net income per capita, we define six types of village-level economy, i.e. "to be extremely poor", "to make a basic living", "to dress warmly and eat one's fill", "to try to enrich (to disengage poverty)", "to be well-off" and "to be affluent". The data of average annual net income of all the 292 villages between 1990 and 2004 in rural Gongyi City, Henan Province were collected, verified and classified. By using standard deviation, coefficient of variation and regression analysis, it is found that the Gongyi's rural economy has boosted up remarkably from the relative-poverty and absolute-poverty stages in 1990 to the well-off in 2004. However, the absolute differences between villages present a trend of enlargement, while the relative differences fluctuating. On the other hand, spatial analysis of village-level economy shows that most villages with relatively high economic development level were located along national expressway and most villages with absolute-poverty lay in remote mountainous areas in 1990. Since the 1990s, the rapid urbanization and industrialization have had strongly positive effects on rural economic growth. Initial economic foundation, natural resources and traditional techniques also contribute to village economy. From the perspective of geography, villages with location advantages, such as near urban center or industrial parks, have more chances for their economic development and the "core-periphery" economic structure has been presented in the process of rural development. 相似文献
110.
湖泊是对环境变化响应敏感的地理单元,湖泊消长与响应机制研究对维持区域生态系统稳定具有重要意义。基于1999—2018年Landsat、气象、水文和农业种植面积等多种数据,在ArcGIS平台中利用改进归一化差异水体指数(MNDWI)及目视修正方法提取了乌兰布和沙漠东南缘湖泊群空间信息,运用统计学方法对主要驱动因子与湖泊消涨的关系进行了分析。结果表明:1999—2018年乌兰布和沙漠东南缘大湖泊(面积大于100 hm2)在面积上占优势,小湖泊(面积小于100 hm2)在数量占优势。趋势分析表明大湖泊面积和数量呈显著性减少趋势(相关系数分别为R=0.624 > R18,0.01=0.561和R=0.648 > R18,0.01=0.561);小湖泊减少趋势不显著。在空间分布格局上,研究区中部是大湖泊稳定分布区,大湖泊数量11~23个,面积2 208~4 581 hm2。研究区湖泊消长主要受到年实际引黄水量、农田面积和地下水埋深的影响。其中,实际引黄(河)水量影响所有湖泊(P≤0.01),而农田面积和地下水埋深分别对大湖泊(P≤0.01)和小湖泊(P≤0.05)影响显著。用这3个因子分别构建的多元回归模型显示,在大、小湖泊面积和数量预测方面,精度分别达到75.7%和60.5%以上。 相似文献