Characterisation of the 1997 Vulcanian explosions of Soufrière Hills Volcano,Montserrat, by video analysis

The activity of Convention at Montserrat Soufrière Hills Volcano, Montserrat, during the period 1995–1999 included numerous violent explosions. Two major cycles of Vulcanian explosions occurred in 1997: a first of 13 explosions between 4 and 12 August and a second of 75 between 22 September and 21 October. The explosions were short-lived events lasting a few tens of seconds during which partial fountain collapse generated pyroclastic surges and pyroclastic flows, and buoyant plumes ascended 3–15 km into the atmosphere. Each explosion discharged on average 3×10⁵ m³ (dense-rock equivalent, DRE) of magma, draining the conduit to depths of 1–2 km. The paper focuses on the first few seconds of three explosions of the 75 that occurred in September/October 1997: 6 October 1997 at 17:50, 7 October 1997 at 16:02 and 9 October 1997 at 12:32. Physical parameters such as exit velocities, magmatic water contents and magma pressures at fragmentation are estimated by following and modelling the ascent of individual momentum-dominated finger jets visible on videos during the initial stages of each explosion. The model treats each finger jet as an incompressible flow sustained by a steady flux of gas and particles during the few seconds of ascent, and produces results that compare favourably with those using a multiphase compressible code run using similar eruptive parameters. Each explosion reveals a progressive increase in eruptive intensity with time, jet exit velocities increasing from 40 m s^–1 at the beginning of the explosion up to 140 m s^–1 after a few seconds. Modelling suggests that the first magma to exit was largely degassed, whereas that discharged after a few seconds contained up to 2 wt% water. Magma overpressures up to ~10 MPa are estimated to have existed in the conduit immediately prior to each explosion. Progressive increases in jet exit velocity with time over the first few seconds of each explosion provide direct evidence for strong pre-eruptive gradients in water content and magma pressure in the upper reaches (probably 100–500 m) of the conduit. Fountain collapse occurred during the first 10–20 s of each explosion because the discharging jets had bulk densities up to 100 times that of the atmosphere and were unable to entrain enough air to become buoyant. Such high eruptive densities were due to the presence of partially degassed magma in the conduit.Editorial responsibility: A. Woods     

降水云中液水含量的空基遥感

在建立不同降水云垂直结构模式的基础上，利用矢量微波辐射传扬模式进行空基云雨遥感的数值试验。结果表明：星载微波辐射计6．9GHz通道对降水云的冰层很不敏感，而对降水云校总液水含量(LWC)非常敏感；辐射亮温(Tb)随LWC呈单调变化关系；进一步考查这个频率下b的两个极化分量差△Tb(＝Tbv—Tbh)和LWC的关系发现，不同云结构(对流云和层状云)对△Tb-LWC关系影响较小。研究分析表明，6．9GHz的v,h两个通道有可能用于遥感降水云的液水总量。     

基于先验知识的GIS路径寻优算法

针对地理信息系统中特定的两点路径寻优问题,提出了一种基于先验知识的快速搜索算法。该算法模拟人脑寻找路径的思维过程,首先针对实际问题建立先验知识库,在路径搜索过程中,利用知识库中的信息剪去不可能的搜索路径,构造出简化的查询树,从而大大提高最优路径的搜索速度。     

利用光谱反射率估算叶片生化组分和籽粒品质指标研究

对可见光至短波红外波段(350—2500nm)冬小麦田间冠层光谱反射率与叶片含氮量间的关系进行了相关分析。结果表明，820—1100nm波段的光谱反射率与叶片含氮量极显著正相关；1150—1300hm波段的光谱反射率与叶片含氮量显著正相关，以上两波段为叶片全氮的敏感波段。对各生育时期叶片全氮与其他生化组分的关系进行了回归分析，并建立了相关的回归方程，显著性检验结果表明，方程具有较高的可靠性。小麦的叶片含氮量可以估算其它生化组分及干物质指标含量，开花期叶片含氮量可用来估测籽粒蛋白质和干面筋等品质指标含量。     

粘粒含量对南京粉细砂液化影响的试验研究

南京粉细砂是一种以片状颗粒成分为主的粉细砂，与通常的圆形颗粒石英砂有一定区别，片状颗粒成分使得南京粉细砂具有各向异性的性质。通过对不同粘粒含量的南京粉细砂进行液化试验，分析其试验结果发现：对于粘粒含量ρc＝5％、10％和15％三种情况，在均压固结情况下，当南京粉细砂达到初始液化时，采用变形标准和孔压标准是一致的；而偏压固结时，只能采用变形标准作为南京粉细砂达到初始液化的标准，此时振动孔压仅达到围压的50％-70％。粘粒含量对南京粉细砂的抗液化强度影响很大，随粘粒含量增加，在不同固结比时，其抗液化强度并不是单调变化，而是在粘粒含量ρc＝10％左右处于一个低谷，其抗液化强度最低。     

NUMERICAL STUDY ON DOMINATING FACTOR AND KEY AREA OF EL NINO CYCLE FORMATION*

A coupled model,which is employed to study the dominating factor and key area of El Nino cycle formation,consists of a dynamical ocean model and a statistical atmospheric model.The coupled model with seasonal forcing successfully reproduces the El Nino event cycle which exhibits quasi-regular oscillations with a preferred period of about 4 years.The results show that the heat content(HC) is transported between the eastern and the western tropical Pacific areas.The spatial distribution of HC anomalies for four phases of the whole cycle clearly shows a possible formation mechanism of El Nino.Experiments further suggest that sea surface temperature in the tropical Pacific and HC in the central tropical Pacific are the most important factors and the central tropical Pacific is the most important area for determining formation of El Nino cycle.     

沙地果树节水渗灌技术的试验研究

果树渗灌是灌溉水通过特殊的透性材料持续缓慢地渗入并浸润土壤，借助土壤毛管水运动原理向果树根系供水。干旱地区沙地渗灌能有效地减少地表蒸发、避免无效渗漏造成的水分损失，提高灌溉水利用率，从而达到节水的目的。在沙地果园采用节水渗灌技术，比传统的大水漫灌和沟灌方式分别节水８３．１％和６３．１％。     

大气中CO2浓度增加对我国农业生产的影响

本文分析了大气中ＣＯ２浓度增加的事实，原因及其发展趋势，结果认为，大气中ＣＯ２浓度上升对我国农业的发展产生了一定的不利影响。因此，为控制大气中ＣＯ２的上升，必须采取相应的有效对策。     

X射线荧光分析技术在喀拉通克铜镍矿井下现场品位测定

文章主要介绍应用 X射线荧光现场取样技术在新疆喀拉通克铜镍矿井下现场测定铜镍品位 ,快速评价矿石质量和降低工人劳动强度的方法和效率     

露天矿边坡实用型专家系统PESOPS V1.0的设计与应用

结合边坡工程和岩质边坡普遍存在的问题，建造了一个露天矿边坡实用型专家系统ＰＥＳＯＰＳ Ｖ１．０。介绍了滑坡预报子系统的原理和方法，通过应用实例表明该子系统适用性强，预报可靠、使用方便。