冰晶核化动力学在地形云中的应用

1.引言控制对流云和地形云增雨的主要因子包括目标云和播撒(或催化)物质的特有性能.对于冷云播撤,成核剂的关键的可变因素包括核化机制、核化时间速率和产量(或成核率).在被催化的云中,有效的核化时间可能十分短促.对流云中上升气流使气溶胶粒子     

锋、急流和对流层顶的结构及动力学

1.高层锋和急流二十世纪初期风筝等携带气象计的温度探测,首次使气象研究工作者观测到锋的垂直结构.Bjerknes和Palmén(1937)运用这些新观测论述了锋的"过渡带"结构,修正了早期的零阶不连续锋的概念.随着高空天气观测网空间分辨率的提高,研究人员优化了他们的关于锋、急流和对流层顶的概念模式.     

ON THE USE OF MOVABLE-BED MODELS FOR RIVER PROBLEMS:A STATE-OF-THE-ART

I. INTRODUCTIONMore than a decade ago, under tile auspices of DELFT HYDRAULICS an overview on the use ofmodels for river problems was given (de Vries & van der Zwaard. 1975). Since then a better understanding of morphological processes in rivers has been obtained, their mathematical formulation hasbeen improved and computer facilities have been expended. Scale models and mathematical models arein use. but their field of application is gradually changing. It seems that the better ma…     

应用地球物理勘查方法探测地下天然洞穴和矿井

现在联系到研究洞穴位置的工程问题来回顾确定洞穴和矿井位置的地球物理方法。其成功与否受到某地施用某方法的穿透力和分辨率所限。如今可看出只用单一物探方法绝对不可能得到与洞穴位置有关一切问题的答案，但对一特定问题施用多种方法会有一定的进展。我们建议对大部分标准物探方法来说，要探的洞穴埋深应小于其有效直径的两倍。有效直径的概念在本文可看出是很重要的。因为洞穴和矿井的存在就影响围岩的物理性质；结果其异常区要比洞穴本身所产生的异常区大得多。所以要探索洞穴和矿井的研究顺序不外乎：室内关于文献资料、图件和航片的研究、野外物化探普查、钻探或山地工程检查、再评查再钻探这么一套。     

现代洋底块状硫化物矿床中金矿化及其与同类古矿床的比较

金是火山成因的块状硫化物矿石的主要副产品之一。在加拿大黄金储量>31吨的各种类型金矿床中,10％的矿床为块状硫化物矿床,平均品位为1—3ppm,有些矿床的品位稍低。最新黄金储量加上已开采的产量达930吨。 块状硫化物在现代洋底的海山脉和扩张中心地区,在热液作用下正不断形成。这些硫化物具     

国际地质科学联合会1989年全球地层表(用地质年代学方法和磁性地层方法标定)

地质年代(距今Ma)┌─┬───┬─────────┬─────────┬────┐│界│系 │ 统 │阶 │地质年代││ │ │I │ │(距今Ma)│└─┴───┼─────────┼─────────┼────┘ │全新统 │ │ ├─────┬───┼─────────┤ │更 ├─上┐│ │ │新 │、VG?│ │ │统 ├─终┘│ │ │ ├WG}%┐│ │ │ │V犷G││ │ │ ├──┘│ │ ┌──┐│ │ │ │ │GSSP│├─────┼───┼─────────┤ └──┘│ 上 │上 │皮亚琴阶 │ │ 新 │ │(Placen艺ian…     

四万年来青藏高原的气候变迁

内陆湖泊,特别是那些大型的淡水湖和盐湖,在漫长的演变历史长河中,对气候环境的反映是相当敏感的。巨厚的沉积物,记录了古气候变迁的丰富信息。盐湖的研究表明,40000年来的重大气候事件,在世界屋脊——青藏高原内部同样有明显的反映。     

Carbonates in CI chondrites: clues to parent body evolution

All CI chondrites are regolith breccias consisting of various types of chemically and mineralogically distinct mineral and lithic fragments (or units). In the CI chondrite Ivuna, for example, four different lithological units were identified and are referred to as lithology I, II, III, and IV. So far, lithologies III and IV have been identified in Orgueil as well. It appears that at least Ivuna and Orgueil consist of the same basic lithologies in different proportions. Carbonates in CIs occur as individual grains within such lithic units or exist as large fragments between them. Carbonate fragments are remnants of former carbonate veins and, in contrast to individual carbonate grains, are not genetically linked to lithological units. Four different types of carbonates (dolomite, breunnerite, calcite, siderite) occur in CIs and they constitute, on average, 5 vol% of each studied section. In this study, carbonates in the CI chondrites Orgueil, Ivuna, Alais, and Tonk were studied petrographically, mineralologically, and chemically. The results clearly indicate that, in contrast to most previous studies, compositional differences exist between dolomites within and among CI chondrites. From these differences it can be derived that (1) several episodes of alteration occurred on the CI parent body, (2) physicochemical conditions during carbonate formation must have been different among CIs, and (3) CI carbonates obviously were formed at low temperatures in equilibrium with surrounding fluid(s). While local compositional changes in fluid(s) on a micrometer to millimeter scale (as reflected by dolomite compositions within CI chondrites) were most likely controlled by the availability of Ca2+ Mg2+, Fe2+, and especially Mn2+ ions in the aqueous solutions, more widespread compositional changes on a meter (or even larger) scale were controlled by variable pH, Eh, CO2 partial pressure, and, especially, temperature conditions (as reflected by the compositional variability of dolomites among CIs).